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51.
By using the unit-cube decomposition to the frequency spaces, we study the Cauchy problem for the nonlinear Schrödinger equation and the nonlinear Klein-Gordon equation. Some global well posedness results are obtained for the small Cauchy data in some modulation spaces . 相似文献
52.
We discuss algebraic properties of the Weyl product acting on modulation spaces. For a certain class of weight functions ω we prove that is an algebra under the Weyl product if p∈[1,∞] and 1?q?min(p,p′). For the remaining cases p∈[1,∞] and min(p,p′)<q?∞ we show that the unweighted spaces Mp,q are not algebras under the Weyl product. 相似文献
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设计了一种与高功率超短脉冲激光放大过程中获得的总增益、增益介质的带宽、激光带宽、脉冲中心波长等参数相关的调制函数,对激光放大过程中的光谱增益窄化进行补偿。此调制函数的优越性在于,对不同性能的激光系统,无需改变调制函数的形式就能适用。通过数值模拟的方法,讨论了在不同增益介质带宽、激光带宽、脉冲中心波长下的补偿效果。此调制函数在高功率超短脉冲激光系统中有良好的应用前景。 相似文献
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S.B. Lisesivdin H. Altuntas A. Yildiz M. Kasap E. Ozbay S. Ozcelik 《Superlattices and Microstructures》2009,45(6):604-611
Experimental Hall data that were carried out as a function of temperature (60–350 K) and magnetic field (0–1.4 T) were presented for Si-doped low Al content (x=0.14) n–AlxGa1−xAs/GaAs heterostructures that were grown by molecular beam epitaxy (MBE). A 2-dimensional electron gas (2DEG) conduction channel and a bulk conduction channel were founded after implementing quantitative mobility spectrum analysis (QMSA) on the magnetic field dependent Hall data. An important decrease in 2DEG carrier density was observed with increasing temperature. The relationship between the bulk carriers and 2DEG carriers was investigated with 1D self consistent Schrödinger–Poisson simulations. The decrement in the 2DEG carrier density was related to the DX-center carrier trapping. With the simulation data that are not included in the effects of DX-centers, 17 meV of effective barrier height between AlGaAs/GaAs layers was found for high temperatures (T>300 K). With the QMSA extracted values that are influenced by DX-centers, 166 meV of the DX-center activation energy value were founded at the same temperatures. 相似文献
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In this study, we have investigated theoretically the binding energies of shallow donor impurities in modulation-doped GaAs/Al0.33Ga0.67As double quantum wells (DQWs) under an electric field which is applied along the growth direction for different doping concentrations as a function of the impurity position. The electronic structure of modulation-doped DQWs under an electric field has been investigated by using a self-consistent calculation in the effective-mass approximation. The results obtained show that the carrier density and the depth of the quantum wells in semiconductors may be tuned by changing the doping concentration, the electric field and the structure parameters such as the well and barrier widths. This tunability gives a possibility of use in many electronic and optical devices. 相似文献
59.
航空稳像光电平台设计 总被引:2,自引:0,他引:2
分析了随机振动对调制传递函数的影响,指出角位移是影响航空成像质量的主要因素.研究了特定条件下可容许的MTF下降,并转变为稳定系统的设计参量,用来指导稳像系统的设计.利用空间机构学及平行四边形平动原理,研制了一种新的无角位移减振稳像平台,满足既无角位移又达到减振要求.根据设计理论给出了设计实例,对频率高于100 HZ的振动,衰减达34dB,并利用动力学软件进行测试仿真,仿真曲线验证无角位移减振的正确性,同时对无角位移机构进行光学测试,结果耦合角度小于8″,可以满足航空成像要求. 相似文献
60.
We experimentally demonstrate an all-optical 10 Gb/s format conversion from non-return-to-zero (NRZ) on-off-keying (OOK) to return-to-zero (RZ)-OOK with tunable duty cycle in the whole C-band using nonlinear polarization rotation (NPR) arising in an semiconductor optical amplifier (SOA). The experimental results show that, by tuning the polarizer at the SOA output, an RZ signal with tunable duty cycle from 33% to 66% could be obtained with an extinction ratio(ER) over 10 dB. In addition, we show that the NRZ-to-RZ conversion with duty cycle of 33-66% can be obtained with less than 1 dB power penalty at the bit error ratio (BER) of 10−9. The device can facilitate the cross-connection between optical transmission networks employing different modulation formats. 相似文献