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Behaviour of Electromagnetic Waves in Different Media and Structures Part 9

Tham khảo tài liệu 'behaviour of electromagnetic waves in different media and structures part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 228 Behaviour of Electromagnetic Waves in Different Media and Structures Source Ave. Power Exposing duration Power density Wm-2 Clinical Biological Symptoms Radar 3GHz high 5h 300-700 Heat Headache Vertigo Radar 9-10GHz 80 sec 600-900 Increasing in Creatine kinase microwave oven 2.45GHz 600W 5 sec Neuropathy wood heater 20kW 20kW 2 sec Burn metallic material wood heater 20kW 20kW 26sec Oedema paresthesia UHF TV antenna 1.75kW 1.75kW 1 to 2.5 min 200 Diarrhoea dysesthesia Table 3. Some reported EMF exposing clinical effects 17 18 3.2 Burning and shocking Burning or shocking can be seen by contacting to conductive materials inside of the EMF. This effect can be separated from indirect effect of EMF on implanted circuits like pace maker or ear-amplifiers. Indeed the induced current in body due to exposing in magnetic field occurred. Such induction especially in lower part of body which contacted to ground has higher amount. Since the ankle cross section is lower than other parts of leg therefore the high current density may cause a burning in tissues there. For frequency lower than 27 MHz an empirical formula used for evaluating such induced current 6 I mA 0.108 X h2 m X f MHz X E v m 17 Further by simulation techniques this burning effect has been modeled. The shoes have a great role in controlling the maximum current in feet that reduce it to 0.6 -0.8 of its peak 9 . Other phenomenon that causes burning is happened when we touch metallic parts which have HF high induced currents on. As soon as the connection occurred the high density of current passes through junction and it could cause a sever injury. Usually we named such effects as shocking and it considered as side effects of EMF on our body. There are lots of instructions and recommendations like the ones issued by WHO IRPA or ICNIRP98 for reducing such effects in sites. 3.3 Non-thermal effects As we have informed the Non-ionizing radiation is considered to be essentially harmless below the levels that cause .