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东北冷暖夏变化特征
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作者 杨青 王国莉 +2 位作者 赵明 孙莹 齐杰 《安徽农业科学》 CAS 北大核心 2010年第23期12907-12909,共3页
对东北地区1961~2002年发生的冷、暖夏事件进行分析。结果表明,东北地区20世纪60~70年代未为冷夏发生期,80年代到90年代初是冷、暖夏交替发生阶段,90年代中后期以后,为暖夏集中出现时期。冷、暖夏具有持续性和群发性特点。冷夏较暖夏... 对东北地区1961~2002年发生的冷、暖夏事件进行分析。结果表明,东北地区20世纪60~70年代未为冷夏发生期,80年代到90年代初是冷、暖夏交替发生阶段,90年代中后期以后,为暖夏集中出现时期。冷、暖夏具有持续性和群发性特点。冷夏较暖夏多,但其中酷暑年却比冷害年多,而且暖夏比冷夏的异常程度要强,影响范围要广。冷夏有4个频发中心,暖夏有2个频发中心,都位于山区和丘陵地带。黑龙江西部、东部既易出现冷夏,也易发生暖夏,长白山脉地区相对而言更易出现冷夏。 展开更多
关键词 冷暖夏 频发中心 群发性 持续性
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Triggered Asynchronous Cooperative Spectrum Sensing Scheme Based on Dempster-Shafer Theory
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作者 肖淑艳 李世银 +2 位作者 李宗艳 崔洁 张晓光 《Journal of Donghua University(English Edition)》 EI CAS 2013年第6期477-481,共5页
Aiming at solving the problems such as time consuming and application limiting presented in the existing synchronous cooperative spectrum sensing schemes,a triggered asynchronous scheme based on Dempster-Shafer(D-S) t... Aiming at solving the problems such as time consuming and application limiting presented in the existing synchronous cooperative spectrum sensing schemes,a triggered asynchronous scheme based on Dempster-Shafer(D-S) theory was proposed.Sensing asynchronously,each cognitive user calculated the confidence measure functions with double threshold spectrum sensing method.When the useful report was received by the fusion center,a fusion process would be triggered.Then the sensing results were fused together based on D-S theory.The analysis and simulation results show that the proposed scheme can improve the spectrum sensing efficiency and reduce the calculation amount of the fusion center compared with the existing schemes. 展开更多
关键词 asynchronous cooperative spectrum sensing ACSS altered-triggered double threshold Dempster-Shafer (D-S) theory
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A simplified tunable frequency interval optical frequency comb generator using a single continuous-wave laser
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作者 刘丽 徐铁峰 +2 位作者 戴振祥 戴世勋 刘太君 《Optoelectronics Letters》 EI 2017年第2期104-107,共4页
We propose and demonstrate a simplified and tunable frequency interval optical frequency comb(OFC) generator based on a dual-drive Mach-Zehnder modulator(DD-MZM) using a single continuous-wave(CW) laser and low-power ... We propose and demonstrate a simplified and tunable frequency interval optical frequency comb(OFC) generator based on a dual-drive Mach-Zehnder modulator(DD-MZM) using a single continuous-wave(CW) laser and low-power radio frequency(RF) driven signal. A mathematical model for the scheme is established. The 21-and 29-mode OFCs with frequency interval ranging from 6 GHz to 40 GHz are obtained under DD-MZM driven by a low-power RF signal within a maximum bandwidth of 1.12 THz. The generated OFCs exhibit spectral flatnesses of less than 0.5 d B and 0.8 d B within bandwidths of 160 GHz and 400 GHz, respectively. 展开更多
关键词 tunable simplified generator modulator flatness bandwidth resonator cascade utilize locked
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