Sunday, August 15, 2010

Medical Technology


We could not imagine medical science without modern treatment methods and highly developed technological procedures.
High-tech developments such as ultrasound equipment or magnetic resonance imaging make it easier for doctors to make a diagnosis and save patients having to undergo stressful and risky examinations.
Where would we be without the ability to use X-rays in making a diagnosis, or the use of lasers to ensure the precision of surgical techniques and treatments?  Technological advances in medical care are simply incredible.


Few discoveries have influenced medicine, technology and science as much as X-rays. On 8th November 1895, the German physicist Wilhelm Conrad Röntgen accidentally discovered them when experimenting with cathode rays. He first called them X-rays because of their unknown physical properties. But then he made a sensational discovery: the rays are electromagnetic, like light or radio waves. They can also be reflected or broken. They differ from light rays, however, in that they are very high-energy, making them able to penetrate solid material.
In November 1895, Röntgen presented the first X-ray photographs at a lecture on X-rays: they showed the bones of a hand – and caused a sensation worldwide. The excitement was so great that X-ray equipment was, for instance, set up in shoe shops so that customers could examine their feet through their new footwear.
The harmful effect of X-rays was not recognised until long after their discovery. A lot of people died from the radiation or became ill with leukaemia. Gradually, people began protecting themselves from the rays.
X-rays can be generated by causing currents of electrons to collide under special conditions. A negatively charged hot cathode emits electrons into an evacuated tube. They are accelerated in an electric field and collide into the positively charged anode. This creates the X-rays which can be seen on photographic material or a fluorescent screen.
An X-ray tube and a luminescent screen are the two most important components in X-ray diagnostic equipment. The object under examination is placed between the source of the rays and the screen. The denser the material, the more radiation is absorbed. The image of the object which appears on the screen (a bone for instance) is light. The exact opposite occurs with more penetrable materials such as skin or muscles.
X-ray diagnosis can help to detect fractures, bone cancer or osteoporosis, an illness which breaks down bone tissue.

Ultrasound waves are generated by crystals oscillating rapidly in an alternating electrical field and have a frequency range of over 20 kilohertz – higher than the human ear can detect.
During a medical ultrasound examination, also termed sonography, a so-called transducer emits the sound waves as well as receiving the sound which is reflected back. A gel allows the high-frequency ultrasound waves to enter the body more easily. Once inside the body they hit different kinds of tissue: air, bones and other mineralised tissues absorb ultrasound almost completely. Consequently, this diagnostic procedure is not suitable for examining the skeleton or the lungs.
Finally, the ultrasound waves return, similar to an echo, and provide three important pieces of information: how long did they travel? How much energy did they consume? From which direction did they come? The computer uses this data, which is provided by a pattern of sound reflection, to generate a two-dimensional image in a matter of seconds.
New ultrasound equipment can even provide three-dimensional images. These 3D pictures, upon which the finest of structures can be discerned, are especially helpful for the exact medical observation of unborn babies in the womb. Ultrasound is not only used for diagnosis, however, but can also be employed for treatment. The sound waves make it possible to carry out very precise operations without destroying too much tissue. In addition, patients undergoing ultrasound treatment are spared painful wounds and scar formation.
The transducer is the most essential part of ultrasound treatment equipment. It can, for instance, destroy a tumour by bundling sound waves at a point which is calculated exactly beforehand. The temperature at this point rises to up to 90 degrees – and with every “shot” several millimetres of the malignant tissue are burnt.Patients with kidney stones are also frequently treated with ultrasound. The shock waves shatter the stone whilst the procedure itself is very gentle on the patient

magnetic Resonance Imaging

With the help of magnetic resonance imaging or nuclear spin resonance tomography, thin, layered images, so-called tomograms, can be generated of any part of the body from any angle without penetrating the body.
The largely stress-free diagnostic procedure which has been applied since the beginning of the 1980s works with strong magnetic fields and short radio impulses. It is based on so-called nuclear spin. This term describes the property of an atomic nucleus to turn on its own axis like a spinning top, changing it into a tiny magnet. The atomic nuclei of hydrogen, which are present in the body in large numbers, behave in exactly the same way.
In magnetic resonance imaging, the body is subjected to a magnetic field, which is approximately 30,000 times stronger than that of the earth. This artificial magnetic field causes the hydrogen atoms in the body to align themselves in one direction rather like compass needles in a magnetic field on earth.
Radio frequency coils send a short impulse with an exactly determined wave length and strength into the body. The pulse causes the aligned hydrogen atoms to spin. Once the impulse has ceased the atoms quickly return to their original positions. During this so-called relaxation time the hydrogen atoms emit resonance signals which are measured.
The signals received serve as the foundation for generating images of the inside of the body with the aid of computer processes such as those already developed for radiography and computer tomography. The various tissues appear on the screen in different levels of brightness. Tissues which are rich in water are very bright, tissues with a low water content are dark. Accordingly, bones can hardly be seen whilst tissues such as muscles, ligaments, tendons and organs can be recognised clearly in finely graduated tones of grey.

The term laser is formed from the initials of the words that describe the specific technology involved: Light Amplification by Stimulated Emission of Radiation. To put it simply, a laser – which generates intensive, highly concentrated beams of light – is a light amplifier.
Its history began in New York in 1960. On 7th July of that year, Theodore H. Maiman demonstrated a lamp which emitted a brilliant red line – a concentrated beam of light. And this is how the world’s first laser, which Maiman had constructed using the precious stone ruby, worked: a flash lamp was shone on the ruby causing some of the ruby molecules to oscillate. The molecules are then in an excited, high-energy state. However, each molecule attempts to return to its normal state. When it does so, it emits a particle of light, also known as a photon – a phenomenon that Albert Einstein had already noted in 1917. Laser light occurs when a very large number of ruby molecules are excited, because they can stimulate each other when they return to their initial state.
As of 1960, the first solid-state and gas lasers were built by Nikolai Gennadiyevich Basov and Alexander Mikhailovich Prokhorov in the Soviet Union and Maiman and All Javan in the United States. The semiconductor laser followed in 1962 and the dye laser some time later.
Today, lasers have become a vital component in many areas of technology. This includes the field of medicine in which laser applications are used every day, ensuring the precision of surgical techniques and treatments. The concentrated artificial light also allows minimal invasiveness; limited side-effects and is therefore especially gentle on the patient.
Intensive laser beams can cut through and cauterise human tissue in fractions of a second without damaging the surrounding tissue. A huge variety of conditions can be treated safely and effectively from vasodilatation to carcinomas of the liver. Over three million eye operations involving laser therapy are performed each year worldwide.

Water Power


   The first hydroelectric power stations for    the production of electricity were built in England as early as 1880. Today there are river power plants, storage power plants, pumped storage power plants, tidal power stations and wave power stations. But as different as these various types of hydroelectric power station are – they all function in similar ways: a power station generally consists of a weir or dam which stores the water in front of the power station or in a reservoir located on higher ground. From here, the water enters the supply pipe or penstock via the intake.
Depending on the type of the turbine, either potential or kinetic energy drives a turbine which is connected to a generator. This finally transforms the mechanical energy into electricity. If the water has passed the turbine it is channeled back into the natural course of the river or the equalising reservoir.
Modern “water wheels” such as the Francis or Pelton turbine can convert almost all of the water power into mechanical energy. They can attain 95 percent efficiency.
Wave Power Stations
The power of the seas can also be used to produce energy. A wave power station on the Scottish island of Islay has been providing electricity since 2001. The technology is actually quite simple: it is not the water which creates energy but the air which the water displaces.
The plant consists of a pipe-shaped reservoir which reaches under the surface of the water. The water level rises and falls with the waves and the air in the pipes is pushed upwards or sucked downwards. The air flow which this creates powers the Wells turbines, named after their inventor.
These turbines are remarkable in that they turn in the same direction whether there is an inflow or outflow of air. Optimum use of wave power is achieved as the turbo generator driven by the turbines also supplies electricity when the waves subside. In this way, the “Limpet 500” produces 500 kilowatts – enough for around 400 households.


Solar Technology

Wind Energy

Suitable areas for large wind power stations are, however, scarce – therefore great hopes are being placed in wind power plants at sea. Worldwide, some offshore wind parks have now been set up, for example in Denmark, Sweden, the Netherlands, Germany and England. The fact that the energy yield at sea is around 50 percent higher is due, amongst other factors, to the fact that water surfaces offer almost no friction to the wind. From a technical point of view, however, the offshore plants are considerably more costly than wind power stations on land because they have to brave high waves, storms and ice. This makes them around 60 percent more expensive than comparable onshore wind parks. In addition, the offshore power stations produce low frequency sounds which could drive away birds, fish and marine mammals.

The Aeroplane

As early as 500 years ago, Leonardo da Vinci devoted himself to the technology of flying and designed various flying devices.
The Englishman Sir George Cayley realized that muscle-powered flying machines based on the flapping motion of birds were leading nowhere and dedicated himself to the construction of gliders. He formulated the main factors of flight – lift, propulsion and steering – which he applied during his attempts at constructing a flying apparatus. One of his assistants finally took off briefly with Cayley’s flying machine in November 1809.
The Berlin engineer Otto Lilienthal undertook the first successful manned flight to cover any distance. In 1891 he took off from a hill with his hand glider and flew a full 25 metres. In the following years, Lilienthal undertook more than 2,000 attempted flights and improved the steering and stability of his flying machines. However, he was unable to carry out his plan of incorporating a petrol engine into a glider; he died in a crash on 9th August 1896.
The trained locksmith, Gustav Weißkopf, who renamed himself Gustave Whitehead after immigrating to the USA, developed a flying machine with wings which could be folded back. On 14th August 1901 (two years before the Wright Brothers) Weißkopf is alleged to have accomplished a successful powered flight. Apparently, he flew a distance of approximately 800 metres with his home-made, engine-powered monoplane “No. 21”.
On 17th December 1903, Orville Wright rose into the air with the biplane “Flyer I”, which had taken off from the ground using engine power, and flew around 36 metres in twelve seconds. Orville and his brother Wilbur undertook a total of four attempted flights on this day – finally remaining in the air for a whole 59 seconds. During these attempts, their Flyer, which was equipped with a 12 horsepower petrol engine as well as a pitch elevator and rudder, flew distances of between 36 and 265 metres. The step towards controlled, powered flight had been taken. In 1904 the brothers were the first to successfully turn a plane and fly in a full circle.
In 1909, the Frenchman Louis Blériot flew over the English Channel. Over 20th and 21st May 1927, the American, Charles Lindbergh, became the first person to fly over the Atlantic alone without stopping. It took him 33½ hours to fly the 5,810 kilometres from New York to Paris. 1939 saw the first jet-powered aircraft, the “Heinkel 178”. In 1947, American Charles Yeager was the first person to break the sound barrier with his rocket aircraft “Bell X-1”. In 1952, the British jet aircraft "De Havilland Comet" heralded the beginning of the jet age in civil aviation. The supersonic jet “Concorde” began regular passenger service in 1976.
Around a hundred years after the first attempts at powered flight, a further chapter in aviation history is now beginning. The "Airbus A380" is expected to enter service in 2006. With 555 seats, the flying giant will be the largest passenger aircraft ever to take off.

Thursday, August 12, 2010

Types of circuits:Analog&Digital

Analog circuits

Hitachi J100 adjustable frequency drive chassis.
Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.
The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.
One rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance. This type of circuit is usually called "mixed signal" rather than analog or digital.
Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output.

Digital circuits

Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. Most digital circuits use two voltage levels labeled "Low"(0) and "High"(1). Often "Low" will be near zero volts and "High" will be at a higher level depending on the supply voltage in use. Ternary (with three states) logic has been studied, and some prototype computers made.
Computers, electronic clocks, and programmable logic controllers (used to control industrial processes) are constructed of digital circuits.Digital Signal Processors are another example.

Electronic devices and components

An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a desired manner consistent with the intended function of the electronic system. Components are generally intended to be connected together, usually by being soldered to a printed circuit board (PCB), to create an electronic circuit with a particular function (for example an amplifier, radio receiver, or oscillator). Components may be packaged singly or in more complex groups as integrated circuits. Some common electronic components are capacitors, resistors, diodes, transistors, etc. Components are often categorized as active (e.g. transistors and thyristors) orpassive (e.g. resistors and capacitors).

What is electronics?

Electronics is the branch of science and technology which makes use of the controlled motion of electrons through different media and vacuum. The ability to control electron flow is usually applied to information handling or device control. Electronics is distinct from electrical science and technology, which deals with the generation, distribution, control and application of electrical power. This distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters, receivers and vacuum tubes.
The concept electronics is used for electronic components, integrated circuits, and electrical systems. Main areas of usage are modern information technology and telecommunications, tools for recording and playing sound and picture, sensors and steering systems, instrumentation and measurement devices. Electronics, information technology and communication technology have undergone immense growth during the past 30 years. Our new technology-based lives are run by the development of miniaturized electrical circuits (microchips) and broadband phone and internet through optical fibers or across wireless channels.

Within transportation we have advanced electrical navigation systems, landing systems for planes, and anti-collision systems for ships and cars. Automatic toll stations across the biggest cities provide money for new roads and environmental friendly traffic. Modern cars are provided with constantly advancing electronics, such as airbag systems, ABS breaks, anti-spin systems and theft alarms.
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