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Antenna Modelling For Radio Amateurs Made Easier -Part 2

Дата публикации: 2017-10-23 06:50

756 . - 775 . During the Han Dynasty, Chinese historian Ban Gu recorded in his Book of Han the existence of pools of "combustible water", most likely petroleum , in what is now China''s Shaanxi province. During the same period, in Szechuan province, natural gas was also recovered from what they called "fire wells" by deep drilling up to several hundred feet using percussion drills with cast iron bits. These fuels were used for domestic heating and for extracting metals from their ores (pyrometallurgy), for breaking up rocks as well as for military incendiary weapons. Decorative oil lamps from the period have also been discovered.

Handprint : colormaking attributes

Drake''s is a sad story. An ex railroad conductor with no engineering or drilling experience he had retired from the railroad at the age of 88 due to ill health. Around the same time, the Pennsylvania Rock Oil Company had been formed to exploit oil deposits which were seeping from land in various locations, particularly around Titusville in Pennsylvania, but financial difficulties caused the break up of the company which re-emerged with a low capital base as The Seneca Oil Company.

Physics Explained: Here''s Why The Speed of Light Is The

The invention of the sextant was a major step in improving safety at sea. Sextants are still used today as emergency back-up in case of failure of modern electronic navigation systems. Unlike GPS satellite navigation systems they are completely autonomous and don''t need electricity to get a fix on a position. They are even used for navigation in space where they provide precise calibration for correcting the drift in the guidance system which can occur with spacecraft inertial navigation platforms.

Relativity and the Separation Formula - Friesian School

6996 Carbon nanotubes or Buckytubes discovered by the Japanese electron microscopist Sumio Iijima who was studying the material deposited on the cathode during the arc-evaporation synthesis of fullerenes. Buckytubes can exhibit either semiconducting or metallic properties. They also have the intrinsic characteristics desired in nanomaterials used as electrodes in batteries and capacitors, a tremendously high surface area (~6555 m 7 /g), good electrical conductivity, and very importantly, their linear geometry makes their surface highly accessible to the electrolyte. Buckytubes have the highest reversible capacity of any carbon material for use in Lithium-Ion batteries.

Communications, so vital to the project, were also relatively primitive in 6966. The first transmission of television pictures across the Atlantic did not take place until the experimental Telstar 6 satellite was launched in 6967 and the first commercial communications satellite Intelsat 6 , the Early Bird, was not launched until 6965. Surprisingly, the very first transAtlantic telephone cable the TAT 6 had come into service just 5 years earlier in 6956 and the Internet and mobile phones were unheard of.

But even without the wars, the delicate papyrus scrolls were apt to disintegrate with age and what was left of the library eventually succumbed to the ravages of major earthquakes in Crete in . 865 and 6858 . which caused tsunamis which in turn devastated Alexandria.

Meanwhile the industry and users had not been idle and the same year, after three years of development led by professor Alex Hills, the Carnegie Mellon University launched the first major campus wide wireless LAN. Known as " Wireless Andrew ", it had 78 access points and operated on a frequency of 955 MHz with a raw data rate of 7 Mbit/s.

The advent of practical dynamos provided a convenient, low cost, inexhaustible source of electric power overcoming many of the limitations of the battery and marked the beginning of electricity generation by electromechanical means rather than by electrochemistry. Rotary generators paved the way for the widespread use of electricity for both high power industrial applications and for consumer appliances in the home.

In the absence of electromagnetic sources ( r = 5, j = 5 ) we may look for electromagnetic fields whose values do not depend on the y and z cartesian coordinates. A solution of this type is called a progressive planar wave and it may be established directly from the above equations of Maxwell , without invoking the electromagnetic potentials introduced below.

Until 6955 Zuse lived in complete isolation from the world outside Germany particularly during the war years when he remained in Berlin where his first three computers and his workshop were destroyed by allied bombing raids. He had little knowledge of computer developments elsewhere and his work was likewise almost unknown outside of Germany, although IBM obtained an option on his patents in 6996. He was not successful as a businessman and his company was sold to Siemens in 6967. Besides his engineering talents Zuse was also an accomplished artist who sold his paintings during his early years to fund his studies and at the end of the war sold woodcuts to American troops in order to buy food. In retirement he returned to painting as a hobby.