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Submitted on: 20 June 2005.
Revised on: 08 July 2005.
Accepted on: 25 July 2005.
Latvian Journal of Physics and Technical Sciences
Submitted on: 07 August 2010.
Revised on: 20 September 2010.
Accepted on: 11 October 2010.
Latvian Journal of Physics and Technical Sciences
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http://reply.papertrans.cn/3/207/20696/20696-35.png
Submitted on: 09 August 2005.
Revised on: 29 August 2005.
Accepted on: 12 September 2005.
Latvian Journal of Physics and Technical Sciences