Industrial, scientific, and medical applications

J. Thunry, Microwaves Industrial, Scientific and Medical Applications, Artech House, Boston, Mass., 1992. 

J. Thuery and E. H. Grant (eds). Microwaves Industrial, Scientific, and Medical Applications. The Artech House microwave library. 1992, Artech House Boston, xviii, 670. 

Secondly, it operates in a highly crowded frequency range because most of the ISM (industrial, scientific, and medical) applications operate in the same range. 

Microwaves are electromagnetic radiation placed between infrared radiation and radio frequencies, with wavelengths of 1 mm to 1 m, which corresponds to the frequencies of 300 GHz to 300 MHz, respectively. The extensive application of microwaves in the field of telecommunications means that only specially assigned frequencies are allowed to be allocated for industrial, scientific or medical applications (e.g., most of wavelength of the range between 1 and 25 cm is used for mobile phones, radar and radio-line transmissions). Currently, in order not to cause interference with telecommunication devices, household and industrial microwave ovens (applicators) are operated at either 12.2 cm (2.45 GHz) or 32.7 cm (915 MHz). However, some other frequencies are also available for heating [1]. Most common domestic microwave ovens utilize the frequency of 2.45 GHz, and this may be a reason that all commercially available microwave reactors for chemical use operate at the same frequency. 

As it was mentioned earlier, mierowaves are electromagnetie waves having a frequeney ranging from 300 MHz and 0.3 THz. Most of the existing apparatuses, however, operate between 400 MHz and 60 GHz, using well defined frequeneies, allocated for industrial. Scientific and Medical (ISM) applications. Among them, the 2.45 GHz is widely used for... 

The key limiting factor is the penetration depth of microwave irradiation, which is only a few centimeters in most solvents at 2.45 GHz. An issue therefore arises in getting sufficient microwave power into the reaction mixture to achieve the desired heating effect. The core of a large reactor vessel will not receive any microwave radiation as it will all have been absorbed by the outer layers. As a result, the center is effectively conductively or convectively heated, and the potential benefits of microwave heating will be lost. Penetration depth does, however, vary with frequency. Only a limited number of Industrial, Scientific, and Medical (ISM) frequencies are allowed so as not to interfere with military and civil aviation frequencies and telecommunications. Alternative frequencies are used for other large-scale applications and thus may provide an alternative solution to the scale-up of micro-wave chemistry. ... 

Microwaves are electromagnetic waves between infrared and ladiofiequency waves. The wavelengths are in the range of 1 cm to 1 m (30 GHz to 300 MHz). To bypass interaction problems with telecommunication, the application of microwaves must be used in defined frequency bands (industrial, scientific and medical frequencies, ISM) see Table 15.2. 

Resonance frequency(ies) the application for which the antenna is intended will specify the frequency or multiple frequencies of resonance of the antenna. For example, industrial, scientific, and medical (ISM) band antennas are required to resonate at one (or more) of the ISM frequencies (868 MHz, 2.45 GHz, 5.8 GHz). An antenna operation requires that the antenna s input impedance is optimally matched to the source impedance, thus the injected power is maximally converted to the form of radiated field. The concept of resonance is strictly related to the reflection coefficient, which is described next. 

Industrial, scientific, and medical bands are reserved portions of the radio spectrum, defined by the ITU Radio Regulations [23], that are employed in body-centric wireless communication applications and, more in general, for other industrial, medical, and scientific applications. The majority of textile antennas developed to date are intended for operation in some of those ISM bands, especially in the 2.45 GHz, by far the most popular for wearable antennas, and 5.8 GHz bands. The first band represents a good trade-off between antenna dimensions (inversely proportional to fiequency) and path loss (increasing with frequency), whereas the second is more convenient when... 

At the frequencies allocated for industrial, scientific and medical purposes between 13.56 and 40 680 MHz, those used for heating applications at 13.56, 27.12, 896 and 2450 MHz are in general use for domestic, commercial and industrial purposes. They may employ substantial field strengths that could cause severe burn injuries, so precautions are necessary to contain the radiation and prevent access into wave guides and resonant chambers and between applicators when the apparatus is energised. This is effected by bolted-on covers which require tools for their removal, or access doors interlocked with the supply so that the supply is off when the door is open. 

This book thus gives an overview of the theory and possible scientific, technical, and medical applications of liquid crystals. Its appeal is not only to physicists and chemists (especially spectroscopists) but equally to those in the manufacturing and processing industries (including electrical engineers). 

Few scientific events have had such an impact on humanity as the discovery of X-rays by Rontgen in November 1895. At that time, even before the nature of these rays was fully xmderstood, there were immediate industrial and medical applications. The first radiographs appeared as early as 1896. The exact nature of X-radiation was only established in 1912, when Max von Laue discovered the phenomenon of diffraction by crystals. He proved that X-rays are in fact electromagnetic waves and, at the same time, he discovered a rather powerful method for studying the structure of materials. In practice, diffraction is applicable to a vast array of scientific problems and technologies. All structures known to date have been determined by diffraction data from X-rays, neutrons, or electrons. Some notable examples are the double-helix structure of DNA, the structures of hemoglobin, vitamins, proteins, minerals, polymers, metals, and ceramics [1]. 

Gas sensors are of importance for a variety of environmental, industrial, medical, scientific and even domestic applications. The gas may be, for example, hazardous to human health, an atmospheric pollutant, or important, in terms of its concentration, for an industrial or medical process. Apart from systems merely providing an alarm signal, it is frequently required to obtain accurate real-time measurements of the concentration of a particular target gas, often in a mixture of other gases. 

Since their discovery more than a century ago, the unique properties of the noble gases have been the subject of much research in theoretical chemistry and physics. These gases have also found many applications as tools for scientific research and many commercial, industrial, and even medical applications as well. These uses are well known, and our further discussion will focus on the role of noble gases in geochemistry. 

---