Nonlinear Zel'dovich effect: Parametric amplification from medium rotation

The interaction of light with rotating media has attracted recent interest for both fundamental and applied studies including rotational Doppler shift measurements. It is also possible to obtain amplification through the scattering of light with orbital angular momentum from a rotating and absorbing cylinder, as proposed by Zel’dovich more than forty years ago. This amplification mechanism has never been observed experimentally yet has connections to other fields such as Penrose superradiance in rotating black holes. Here we propose a nonlinear optics system whereby incident light carrying orbital angular momentum drives parametric interaction in a rotating medium. The crystal rotation is shown to take the phase-mismatched parametric interaction with negligible energy exchange at zero rotation to amplification for sufficiently large rotation rates. The amplification is shown to result from breaking of anti-PT symmetry induced by the medium rotation

Roadmap on ultrafast optics

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Ｅｆｆｅｃｔｓ ｏｆ Ｓｔｒａｗ Ｍｕｌｃｈｉｎｇ ａｎｄ Ｓｔｕｂｂｌｅ ｏｎ Ｓｏｉｌ ａｎｄ

通过人工模拟降雨试验,研究秸秆覆盖和留茬在玉米生育期的水土保持效应。结果表明:覆盖和留茬在玉米不同生育期均可有效减少土壤侵蚀,覆盖的效果更为明显,其产沙量最大可减少75%,留茬的产沙量最大可减少29%。相同秸秆用量下实行覆盖的水土保持效应较留茬明显。覆盖结合留茬减弱土壤侵蚀的效果明显,在玉米各生育期的产沙量均有大幅减少,低覆盖高留茬减幅最大为85%,高覆盖低留茬减幅最大为78%;在抽穗期对径流强度也有削弱,低覆盖高留茬的径流量减少23%,高覆盖低留茬减少15%,相同秸秆用量下低覆盖高留茬对水土流失的抑制较高覆盖低留茬明显。Ａｂｓｔｒａｃｔ：Ｅｘｐｅｒｉｍｅｎｔｓ　ｕｎｄｅｒ　ｓｉｍｕｌａｔｉｏｎ　ｒａｉｎｆａｌｌ　ｗｅｒｅ　ｃｏｎｄｕｃｔｅｄ　ｔｏ　ｓｔｕｄｙ　ｅｆｆｅｃｔｓ　ｏｆ　ｓｔｒａｗ　ｍｕｌｃｈ　ａｎｄ　ｓｔｕｂｂｌｅｏｎ　ｓｏｉｌ　ａｎｄ　ｗａｔｅｒ　ｃｏｎｓｅｒｖａｔｉｏｎ　ａｔ　ｄｉｆｆｅｒｅｎｔ　ｇｒｏｗｔｈ　ｓｔａｇｅｓ　ｏｆ　ｃｏｒｎ．Ｒｅｓｕｌｔｓ　ｓｈｏｗｅｄ　ｔｈａｔ　ｂｏｔｈ　ｓｔｒａｗ　ｍｕｌｃｈｗｈｉｃｈ　ｈａｄ　ｍｕｃｈ　ｍｏｒｅ　ｏｂｖｉｏｕｓ　ｅｆｆｅｃｔｓ，ａｎｄ　ｓｔｕｂｂｌｅ　ｗｏｕｌｄ　ｅｆｆｉｃｉｅｎｔｌｙ　ｄｅｌａｙ　ｔｈｅ　ｒｕｎｏｆｆ　ｉｎｉｔｉａｔｉｎｇ　ｔｉｍｅ　ａｎｄ　ｒｅｄｕｃｅ　ｔｈｅ　ａｍｏｕｎｔ　ｏｆ　ｓｏｉｌ　ｅｒｏｓｉｏｎ．Ｔｈｅ　ｅｆｆｅｃｔ　ｏｆ　ｓｔｒａｗ　ｍｕｌｃｈ　ｗａｓ　ｍｏｓｔ　ｄｉｓｔｉｎｃｔ　ａｔ　ｔｈｅ　ｊｏｉｎｔｉｎｇ　ｓｔａｇｅ　ｗｉｔｈ　ｔｈｅｒｕｎｏｆｆ　ｉｎｉｔｉａｔｉｎｇ　ｔｉｍｅ　ｄｅｌａｙｅｄ　ｂｙ　９６％ｃｏｍｐａｒｅｄ　ｗｉｔｈ　ＣＫ，ｔｈｅ　ａｍｏｕｎｔ　ｏｆ　ｓｏｉｌ　ｅｒｏｓｉｏｎ　ｒｅｄｕｃｅｄ　ｂｙ　７５％，ａｔ　ｔｈｅｓｅｅｄｉｎｇ　ｓｔａｇｅ　ａｎｄ　ｔｈｅ　ａｍｏｕｎｔ　ｏｆ　ｃｕｍｕｌａｔｉｖｅ　ｒｕｎｏｆｆ　ｗａｓ　ｒｅｄｕｃｅｄ　ｂｙ　１５％ ａｔ　ｔｈｅ　ｈｅａｄｉｎｇ　ｓｔａｇｅ　ａｔ　ｔｈｅ　ｓａｍｅｔｉｍｅ．Ｔｈｅｓｅ　ｍｅａｓｕｒｅｓ　ｏｆ　ｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｓｔｕｂｂｌｅ　ａｌｓｏ　ｄｅｌａｙｅｄ　ｔｈｅ　ｒｕｎｏｆｆ　ｉｎｉｔｉａｔｉｎｇ　ｔｉｍｅ　ａｎｄ　ｒｅｄｕｃｅｄ　ｔｈｅ　ａｍｏｕｎｔ　ｏｆ　ｓｏｉｌ　ｅｒｏｓｉｏｎ　ｅｆｆｉｃｉｅｎｔｌｙ　ａｔ　ｔｈｅ　ｄｉｆｆｅｒｅｎｔ　ｇｒｏｗｔｈ　ｓｔａｇｅｓ　ｏｆ　ｃｏｒｎ，ｅｓｐｅｃｉａｌｌｙ　ａｔ　ｔｈｅ　ｊｏｉｎｔｉｎｇｓｔａｇｅ．Ｔｈｅ　ｒｕｎｏｆｆ　ｉｎｉｔｉａｔｉｎｇ　ｔｉｍｅ　ｗａｓ　ｄｅｌａｙｅｄ　ｂｙ　１．３６ｔｉｍｅｓ　ｕｎｄｅｒ　ｌｏｗ　ｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｈｉｇｈｓｔｕｂｂｌｅ，ａｎｄ　ｂｙ　５２％ｕｎｄｅｒ　ｈｉｇｈ　ｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｌｏｗ　ｓｔｕｂｂｌｅ，ｍｅａｎｗｈｉｌｅ，ｔｈｅ　ａｍｏｕｎｔ　ｏｆ　ｓｏｉｌ　ｅｒｏｓｉｏｎ　ｗａｓ　ｒｅｄｕｃｅｄ　ｂｙ　８５％ａｎｄ　７８％，ｒｅｓｐｅｃｔｉｖｅｌｙ　ｃｏｍｐａｒｅｄ　ｗｉｔｈ　ＣＫ　ａｔ　ｔｈｅ　ｊｏｉｎｔｉｎｇ　ｓｔａｇｅ　ｏｆ　ｃｏｒｎ．Ａｎｄ　ａｔｔｈｅ　ｈｅａｄｉｎｇ　ｓｔａｇｅ，ｔｈｅ　ｃｕｍｕｌａｔｉｖｅ　ａｍｏｕｎｔ　ｏｆ　ｒｕｎｏｆｆ　ｗａｓ　ｒｅｄｕｃｅｄ　ｂｙ　２３％ａｎｄ　１５％，ｒｅｓｐｅｃｔｉｖｅｌｙ　ｕｎｄｅｒ　ｌｏｗｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｈｉｇｈ　ｓｔｕｂｂｌｅ　ａｎｄ　ｈｉｇｈ　ｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｌｏｗ　ｓｔｕｂｂｌｅ，ｂｏｔｈ　ｏｆ　ｗｈｉｃｈｄｅｍｏｎｓｔｒａｔｅｄ　ｄｉｓｔｉｎｃｔ　ｅｆｆｅｃｔｓ　ｏｎ　ｓｏｉｌ　ａｎｄ　ｗａｔｅｒ　ｃｏｎｓｅｒｖａｔｉｏｎ，ｅｓｐｅｃｉａｌｌｙ　ｌｏｗ　ｓｔｒａｗ　ｍｕｌｃｈ　ｃｏｍｂｉｎｉｎｇ　ｗｉｔｈ　ｈｉｇｈｓｔｕｂｂｌｅ

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