Radio communications

Because of the low operating temperature and ease of fabrication for low power units, PFFCs are the most likely fuel cell to be introduced in portable power packs. PFFCs in sizes of 300—500 W are being considered as a power source, eg, 4-h duration, 300 W, 1.2 kW, for the modem soldier operating in the enclosed environment of a self-contained protective suit, which has faciUties for air conditioning, radio communication, etc. Analytic Power Corp. (Boston) is assessing the use of PFFCs for this appHcation. 

It should be noted that, whereas ferroelectrics are necessarily piezoelectrics, the converse need not apply. The necessary condition for a crystal to be piezoelectric is that it must lack a centre of inversion symmetry. Of the 32 point groups, 20 qualify for piezoelectricity on this criterion, but for ferroelectric behaviour a further criterion is required (the possession of a single non-equivalent direction) and only 10 space groups meet this additional requirement. An example of a crystal that is piezoelectric but not ferroelectric is quartz, and ind this is a particularly important example since the use of quartz for oscillator stabilization has permitted the development of extremely accurate clocks (I in 10 ) and has also made possible the whole of modern radio and television broadcasting including mobile radio communications with aircraft and ground vehicles. 

Two-way radios, as discussed here, are limited to a direct unit-to-unit radio communication, either via single unit-to-unit transmission and reception, or via multiple handheld units to a base station radio contact and distribution system. Radio frequency spectrum limitations apply to all handheld units, and are directed by the FCC. This also distinguishes a handheld unit from a base station or base station unit (such as those used by an amateur [ham] radio operator), which operates under different wave-length parameters. 

At 11 09 A.M., a high-LEL detector in the catalyst preparation area sounded on the DCS. The lead outside operator was contacted by radio communications to investigate the problem. He said he was just leaving the Reactor No. 1 area and would go right to the catalyst preparation area. The thunderstorm had passed overhead and the rain was diminishing. At about 11 10 A.M., a whooshing noise (assumed to be the fireball) was heard by many and the heat detector for the automatic water-spray sprinkler coverage in this area alarmed in the control room. The lead outside operator did not respond when called on the radio. 

SEMICONDUCTORS. Materials and devices known as semiconductors have been the backbone of the electronics industry for many years. Semiconductors did not enter the industry in a major way, however, until several years after the vacuum tube (valve) had been well established. In terms of perspective, it is interesting to note that at least one. semiconductor device predated the vacuum tube in the early days of radio communication. This was the then familiar galena crystal and accompanying whisker used in early crystal set radio receivers. 

Mori ow, D., Leirer, V., and Yesavage, J., Tire influence of alcohol and aging on radio communication during flight, Aviat. Space Environ. Med., 61, 12, 1990. 

Voices floated out into the corridor, along with the light. One of them passed through the unmistakable filter of radio communication. 

Vapor-protective suit (meets NFPA 1991) pressure-demand, full-face SCBA inner chemical-resistant gloves chemical-resistant safety boots two-way radio communication... 

The rapid growth of satellite and mobile radio communications has led to a requirement for narrow band, frequency-stable filters and oscillators. Selectivity and stability are necessary to ensure that signals are confined to closely defined allotted frequency bands and to prevent the intrusion of unwanted signals which would interfere with the satisfactory performance of the system. Antennae are also critical components of any wireless communications system. The need for compactness in satellite and hand-held mobile systems is self-evident. 

There are two aspects to emergency communications the actual equipment used to communicate information about the incident and the types of communications or information-sharing required. The RCRA has specific requirements for the types of emergency communication equipment (alarm systems, phone or radio communications) that must be present. Under the EPCRA, facilities must provide information about their operations and substances used or stored on site when the Local Emergency Planning Committee (LEPC) or State Emergency Response Commission (SERC) requests it. If the facility uses or stores extremely hazardous substances (EHSs) in reportable quantities, it must appoint a representative to the LEPC. Several laws require that a copy of the ERP be made available to employees and... 

EMA opened their office, but unfortunately only the Director and one other volunteer had been able to make it in. Radio communications were down and each township was trying to run independent emergency operations. 

Direct registration of ionising radiation in the environment in the dosimetric points disposed in the location around the enterprises, these points being supplied with microprocessing equipment controlled by sensors, having telephone or radio communication with the central computer. 

Cady in World War II realized that such a mechanical resonance of a vibrating crystal could be used in frequency control. This discovery had an important influence on radio communications.Alternating electric fields, such as those generated by the radio tubes of the time, were applied to plates of piezoelectric crystals and the expansions and contractions of the plates were caused to react on electrical circuits. If the natural frequency of the mechanical vibration of the quartz plate coincided with the frequency of oscillation of the electric circuit, resonance between the two took place and energy was acquired by the mechanical oscillators. Later. Rochelle salt and barium titanate, which are each both ferroelectric and piezoelectric, were used. ° In ferroelectric crystals, the polarization or dipole moment is reversed or reoriented upon application of an electric field. Ferroelasticity is another property displayed by some crystals in which stress can cause the interconversion between two stable orientational states. These physical properties of crystals are of great use in modern technology. 

Design a mechanism by which radio communications can be maintained between the hospital, the incident commander, and the senior medic at the chemical incident site. 

Radio Communication Radar Optical Communication Medical Imaging Astrophysics ... 

With the extension of radio-communication to ultra-high frequencies the use of point-contact crystal rectifiers in telecommunication circuits has become an established practice. Both silicon and germanium (p. 174) crystal rectifiers are now in use. 

France and studied history at the Sorbonne. During World War I, he was stationed in the Eiffel Tower as a radio engineer. Intrigued by his exposure to radio communications, he returned to school after the war, earned a Ph.D. in physics, and became a professor of theoretical physics at the Faculte des Sciences at the Sorbonne. He received the Nobel Prize in physics in 1929, five years after obtaining his degree, for his work that showed electrons to have properties of both particles and waves. In 1945, he became an adviser to the French Atomic Energy Commissariat. 

Above approximately 80 km, the prominent bulge in electron concentration is called the ionosphere. In this region ions are created from UV photoionization of the major constituents—O, NO, N2 and O2. The ionosphere has a profound effect on radio communications since electrons reflect radio waves with the same frequency as the plasma frequency, / = 8.98 X lO /iy, where is the electron density in cm [147]. The... 

The standard weapon appeared to be the British Lee-En-field rifle. There were a number of small machine pistols of local manufacture, short-range weapons not very accurate beyond 50 yards. I saw Bren guns (automatic rifles) and a few heavy machine guns. Mines and other demolition material were also homemade and seemed of good quality. Communication equipment included a number of pack sets and walkie-talkies, and radio communication was constant between all major military headquarters. There was some motor transport, but no truck-mounted radio transmitters or power plants. 

This is just another example of the need for American naval officers on this explosive assignment to be constantly prepared to meet any emergency that may arise, and to try to guess if possible where the next emergency may make its appearance so that they will not be too far away if they are needed. Of course, with radio communications what they are today, far less is left to the initiative of the commander on the spot than... 

Static loads encompass heaters, battery chargers, uninterruptible power supplies, lighting distribution boards, socket outlets, cathodic protection, navigational aids, computers, public address, radio communication and the like. Excluded are loads that are not predominantly composed of motors. The load may have fractional kW motors for cooling fans. 

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