Open But not Permissive
yu jun-min (journal editorial department of neijiang teachers college; neijiang; sichuan 641112)
..............page:70-72
..............page:100-101
..............page:123-124
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..............page:102-104
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..............page:131-132
The Parallel Connection of UPS
qu kejian; ren baoping (xiangfan vocational and technical college; xiangfan; hubei 441050; aerospale life-support industries co. ltd; xiangfan; hubei 441003)
..............page:109-111
..............page:112-114
..............page:125-126
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..............page:107-108,114
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