Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and ape...Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and aperiodic flows is investigated through visible experiments and numerical simulations.The distribution of stretching is found to be much more uniform for apeiodic flows and mixing efficiency of aperiodic flows is higher than periodic flows.Among the several aperiodic sequences,the SB sequence is the best one.展开更多
利用Melnikov方法研究了Bardeen-Anti de Sitter(AdS)黑洞对周期性微扰的热力学响应以及混沌的发生与演化,探讨了Quintessence暗能量对黑洞的影响.根据规范/引力对偶与扩展相空间的思想,将黑洞看作一个可压缩、具有微小黏性、各向同性...利用Melnikov方法研究了Bardeen-Anti de Sitter(AdS)黑洞对周期性微扰的热力学响应以及混沌的发生与演化,探讨了Quintessence暗能量对黑洞的影响.根据规范/引力对偶与扩展相空间的思想,将黑洞看作一个可压缩、具有微小黏性、各向同性的液体系统.首先对Bardeen-AdS黑洞的相变旋节区施加时间周期性微扰,当微扰的临界振幅γ大于临界振幅γ_(c)时,黑洞会产生热力学混沌现象,该临界值由非线性电磁场(具体体现为磁单极荷β)和初始温度T_(0)共同决定.然后对黑洞施加空间周期性微扰时,任意大小的微扰振幅均会导致黑洞相空间中出现混沌现象.考虑Kiselev的各向同性唯象模型,我们发现Quintessence暗能量对其内包裹黑洞的影响类似于一种热力学意义下的增益/阻尼机制.展开更多
针对强噪声中微弱BPSK信号的盲检测问题,论文从周期信号入手,指出相差固定时由于输入信号与Duffing系统内置信号存在频差,将导致系统进入周期性混沌状态。对BPSK信号,由于信号本身相位的变化,Duffing系统相轨迹演化将进入间歇性混沌状...针对强噪声中微弱BPSK信号的盲检测问题,论文从周期信号入手,指出相差固定时由于输入信号与Duffing系统内置信号存在频差,将导致系统进入周期性混沌状态。对BPSK信号,由于信号本身相位的变化,Duffing系统相轨迹演化将进入间歇性混沌状态。论文通过采用时序图法和S变换提取时序输出包络来判断Duffing系统间歇性混沌状态,分析了方程控守频带范围,并建立正相振子和反相振子检测方程,最后提出了基于Duffing振子和S变换的微弱BPSK信号盲检测模型。仿真实验结果表明,在信噪比大于-40 d B时,可以稳定实现微弱BPSK信号的盲检测。展开更多
文摘Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and aperiodic flows is investigated through visible experiments and numerical simulations.The distribution of stretching is found to be much more uniform for apeiodic flows and mixing efficiency of aperiodic flows is higher than periodic flows.Among the several aperiodic sequences,the SB sequence is the best one.
文摘利用Melnikov方法研究了Bardeen-Anti de Sitter(AdS)黑洞对周期性微扰的热力学响应以及混沌的发生与演化,探讨了Quintessence暗能量对黑洞的影响.根据规范/引力对偶与扩展相空间的思想,将黑洞看作一个可压缩、具有微小黏性、各向同性的液体系统.首先对Bardeen-AdS黑洞的相变旋节区施加时间周期性微扰,当微扰的临界振幅γ大于临界振幅γ_(c)时,黑洞会产生热力学混沌现象,该临界值由非线性电磁场(具体体现为磁单极荷β)和初始温度T_(0)共同决定.然后对黑洞施加空间周期性微扰时,任意大小的微扰振幅均会导致黑洞相空间中出现混沌现象.考虑Kiselev的各向同性唯象模型,我们发现Quintessence暗能量对其内包裹黑洞的影响类似于一种热力学意义下的增益/阻尼机制.
文摘针对强噪声中微弱BPSK信号的盲检测问题,论文从周期信号入手,指出相差固定时由于输入信号与Duffing系统内置信号存在频差,将导致系统进入周期性混沌状态。对BPSK信号,由于信号本身相位的变化,Duffing系统相轨迹演化将进入间歇性混沌状态。论文通过采用时序图法和S变换提取时序输出包络来判断Duffing系统间歇性混沌状态,分析了方程控守频带范围,并建立正相振子和反相振子检测方程,最后提出了基于Duffing振子和S变换的微弱BPSK信号盲检测模型。仿真实验结果表明,在信噪比大于-40 d B时,可以稳定实现微弱BPSK信号的盲检测。
