Oven, microwave

The US is currently the world s largest market for microwave ovens in terms of volume sales. Western Europe is the second largest market followed by Japan. 

The importance of microwave oven sales to the major national markets varies significantly, and these variations appear to be related to cooking habits rather than wealth or economic development. For example, microwaves account for a high of 92.9% of sales of large cooking appliances in South Korea, compared to a low of just 15.5% of sales in Italy. In markets like the US and Canada, the importance of microwaves comes from the popularity of convenience foods. 

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The other attraction is the method itself clay, a Sears microwave oven and the most lightning-quick results ever imagined Someone sent Strike this method via fax, but dumbass Strike did not get the person s name . But you know who you are. Bra ... 

Carmosini, N. Ghoreshy, S. Koether, M. C. The Gravimetric Analysis of Nickel Using a Microwave Oven, ... 

A procedure for using a microwave oven to digest samples of Ni ore and to dry precipitates of nickel-dimethylgloxime is described in this experiment. 

This article describes conditions for using a household microwave oven to dry precipitates for the determination of Gh as AgGl, the determination of S04 as BaS04, and the determination of Ga + as GaG204 H2O. 

The frequency bands at 915 and 2450 MHz (2375 MHz in the past in eastern Europe) are the most developed bands for microwave power apphcations. Microwave ovens are almost all at 2450 MHz. Many industrial heating appHcations are at 915 MHz. After the 1979 WARC, eastern Europe adopted 2450 MHz in place of 2375. 

The most dramatic evolution of a microwave power source is that of the cooker magnetron for microwave ovens (48). These magnetrons are air-cooled, weigh 1.2 kg, generate weU over 700 W at 2.45 GHz into a matched load, and exhibit a tube efficiency on the order of 70%. AppHcation is enhanced by the avaHabiHty of comparatively inexpensive microwave power and microwave oven hardware (53). The cost of these tubes has consistently dropped (11) since their introduction in the eady 1970s. As of this writing (ca 1995), cost is < 15/tube for large quantities. For small quantities the price is < 100/tube. 

Some power tubes can be operated without the need for a protective ferrite isolator. One example is the cooker magnetron (700 W) used in modern microwave ovens (57). At higher power levels, such as 25 kW, it is more common to employ a protective ferrite device, particularly in the form of a circulator (58), as shown in Figure 3. This results in a power loss equivalent to a few percentage points in system efficiency. The ferrite circulator prevents reflected power from returning to the power tube and instead directs it into an auxiHary dummy load. The pulling of tube frequency is thus minimised. 

The use of inverter-type power suppHes (63) in place of doubler-type 6O-H2 suppHes results in significant reduction in the weight of microwave ovens. Disadvantages are primarily cost for the consumer market in addition to somewhat less efficiency and increased noise. Their use in commercial or industrial equipment is more attractive. 

The price of cooker magnetrons at ca 700 W was in the range of several hundred dollars in the 1960s (11). As of the mid-1990s, this price is < 15. Total sales of microwave ovens worldwide exceed 20 x 10 /yr. The majority of homes in Japan and the United States have microwave ovens (94). European homes should foUow before the year 2000 (95). 

The nature of potential exposure ha2ards of low level microwave energy continues to be investigated (116—118). In the United States, leakage emission from microwave ovens is regulated to the stringent limit of 5 mW/cm at 5 cm (119). There is no federal limit on emission from industrial systems but the IMPI has set a voluntary standard which specifies 10 mW/cm at 5 cm (120). Emission values are equivalent to personnel exposures at several meters, well below limits that had previously prevailed in eastern Europe. This conclusion, derived for microwave ovens, should be vaUd for all microwave systems (121). 

Food. The most successful appHcation of microwave power is that of food processing (qv), cooking, and reheating. The consumer industry surpasses all other microwave power appHcations. Essentially all microwave ovens operate at 2450 MH2 except for a few U.S. combination range models that operate at 915 MH2. The success of this appHance resulted from the development of low cost magnetrons producing over 700 W for oven powers of 500-800 W (Table 3). 

The mote general food processing appHcations requite data on dielectric and thermal properties (139). Considerable effort has been expended by food companies in the design of food for the microwave oven. These principles have been reviewed (140). The microwave oven at 2450 MH2, used for reheating, cooking, and thawing foods, may also be used for drying (qv), eg, flowers or food materials (141). Commercial microwave ovens ate used extensively in restaurants and fast-food estabUshments. 

P. E. Gawthrop and co-workers, Kadio Spectrum Measurements of Individual Microwave Ovens, Vols. 1 and 2, NTIA Reports 94-303-1 and 94-303-2, U.S. Dept, of Commerce, Washington, D.C., Mar. 1994. 

To speed up the molding process, the required amount of molding powder or granules is often pressed iato a block and prewarmed before placing it ia the mold. Rapid and uniform heating is accompHshed ia a high frequency preheater essentially an iadustrial microwave oven. The prewarmed block is then transferred to the hot mold, pressed iato shape, and cured. 

In electrical porcelains (often called steatite bodies), high purity talc products with low levels of alkali metals ate preferred. A typical steatite is made from 85% talc, 10% plastic kaolin, and 5% BaCO. Steatites ate used as insulators on high voltage equipment such as automotive starters, microwave oven generators, and laser generators. 

The most universal method for sample destmction before SPh metal determination (Ee, Mo, A1 and etc.) is the sulfur acid digestion at high temperature by Kjeldall. It can be enforced by microwave decomposition in the microwave oven. 

General Electric now also offer polyetherimide-polycarbonate blends. Although these materials are not transparent and have a lower specification than the basic polyetherimide, they are less expensive and find use in microwave oven trays and automotive reflectors. 

Polycarbonates based on tetramethylbisphenol A are thermally stable and have a high Vicat softening point of 196°C. On the other hand they have lower impact and notched impact resistance than the normal polymer. Blends with styrene-based polymers were introduced in 1980, and compared with PC/ABS blends, are claimed to have improved hydrolytic resistance, lower density and higher heat deflection temperatures. Suggested applications are as dishes for microwave ovens and car headlamp reflectors. 

Other, more recently developed, uses include microwave oven parts, transparent pipelines, chemical plant pumps and coffee machine hot water dispensers. One exceptional use has been to produce, by an extrusion moulding process, very large rollers for textile finishing for use where cast nylons cannot meet the specification. Also of growing interest are medical equipment applications that may be repeatedly steam-sterilised at 134°C, filtration membranes and cartridges for ink-jet printers. 

A further substantial development, although not on the scale of the bottle and film markets, had been the use of thermoformed PET sheet for menu trays. The high heat distortion temperature of 220°C allows these products to be used in both traditional and microwave ovens. 

AI2O3, H2O, hexanes, 81-98% yield. These conditions are selective for the primary derivative. TBDPS and TMS ethers are also cleaved. The use of alumina in a microwave oven is also effective (68-93% yield). ... 

The previous methods used commercial microwave ovens. When a Smith Synthesizer was employed where one could control temperature and pressure, further improvements in time and yield were noted for the conversion of 95 and 82 into 96. Optimal conditions included the use of aqueous ammonium hydroxide as solvent and nitrogen source. The method was efficient enough to execute on a 4 x 6 array using the dicarbonyl and the aldehyde as points of diversity. The library of 24 compounds was obtained in 39-89% yields and 53-99% purity. 

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