1. Warily, the Sydney closed to within a nautical mile, challenging the Kormoran to show a secret signal and prove she was a friend.
悉尼号小心翼翼地靠到距它一海里的地方，要求Kormoran出示秘密信号，以证明它是朋友。
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2. At present, the system research is a challenging problem both at home and abroad as it involves complicated signal processing and hardware designing technology.
由于涉及复杂的信号处理和硬件设计技术，系统的研制目前在国内外都是一个具有挑战性的课题。
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3. The emerge of high performance ADC puts mixed signal testing field to a challenging situation.
高性能adc产品的出现，给混合信号测试领域带来前所未有的挑战。
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4. The emerge of high performance ADC puts mixed signal testing field to a challenging situation.
