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We show the formation of ultraslow bright and dark optical solitons in a cascade-type three-level system of GaAs/AlGaAs multiple quantum wells (MQWs) structure based on the biexciton coherence in the transient optical response, and study analytically and numerically with Maxwell–Schrödinger equations. The calculated velocity of bright and dark optical solitons are Vg = 2.7 × 104 ms? 1 and Vg = 8.91 × 104 ms? 1, respectively. Such investigation of ultraslow optical solitons in MQWs may provide practical applications such as high-fidelity optical delay lines and optical buffers in semiconductor quantum wells structure, because of its flexible design. 相似文献
234.
Identifying Radix Curcumae by using terahertz spectroscopy 总被引:1,自引:0,他引:1
Hong Li ShaoQing Du Le Xie Lin Chen Yan Peng YiMing Zhu Tao Wu Han Li Ping Dong JiaTai Wang 《Optik》2012,123(13):1129-1132
The absorption spectra from 0.2 THz to 1.6 THz of four kinds of similar Chinese herbs, including huangyujin, lvyujin, guiyujin and wenyujin, have been investigated by terahertz time-domain spectroscopy (THz-TDS). Furthermore, by using support vector machines (SVM) method, the linear kernel function, the polynomial kernel function, and the radial basis kernal function are employed for separating four kinds of Radix Curcumae. The calculated results show that the accuracy of discrimination for these four kinds of Chinese herbs is 100%. 相似文献
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236.
A bronze Pan (water vessel), dating back to the 4th–3rd century BC, was excavated at Jiuliandun in Hubei Province, central southern China, in 2002. The Pan attracts wide attention among the Chinese archaeologists and conservators for its uniqueness in style and color, which turns out to be due to a black‐brown film of about 1 mm thickness. In the present work, a combined use of X‐ray fluorescence (XRF), micro‐Raman, and X‐ray diffraction (XRD) was employed to determine both chemical and physical compositions of the Pan's film. The results are summarized as follows: (1) The film, as XRF analysis indicates, has high concentrations of chromium (Cr) and iron (Fe); (2) Both Raman and XRD analyses suggest that the element Cr probably exists in the film mainly in the form of chromium oxide (Cr2O3). Raman analysis also implies the presence of PbCrO4·PbO in the film; (3) XRD analysis suggests that the element Fe exists in the film in the form of magnetite (Fe3O4). Based on these analytical results and Chinese historical records, we propose that, as early as in the 3rd century BC, people in central southern China might have discovered and intentionally used chromium minerals for bronze surface treatment (such as coating). The source of chromium minerals used in this period was likely Cr‐spinel minerals from meteorites. More work remains to be done to test the possibility of using Cr‐spinel minerals for bronze production and decoration. Other issues, such as the possibility of forming a chromium‐rich film during the underground burial, also need to be solved. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
237.
Xinnan Wang Shuping Xu Haibo Li Jinlong Tao Bing Zhao Weiqing Xu 《Journal of Raman spectroscopy : JRS》2012,43(3):459-463
A three‐dimensional surface‐enhanced Raman scattering (SERS) substrate via the self‐assembly of properly sized Au nanoparticles in anodic aluminum oxide templates was designed and prepared. Au nanoparticles first underwent hydrophobic surface modification. Then, the hydrophobic Au nanoparticles self‐assembled, aggregated and formed many hot spots in the anodic aluminum oxide templates through a supramolecular interaction. We chose thiophenol as a probe molecule to evaluate the SERS enhancement ability of this three‐dimensional substrate. The enhancement factor was calculated to be 4.6 × 106 under the radiation of a 785‐nm laser. By further comparing SERS signals from different points on the same substrate, we confirmed that this substrate possessed good reproducibility and could be applied for SERS detection. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
238.
From a complex network perspective, this study sets out two aims around the US airport network (USAN) which is built from en-route location information of domestic flights in the US. First, we analyze the structural properties of the USAN with respect to its binary and weighted graphs, and second we explore the airport patterns, which have wide-ranging implications. Results from the two graphs indicate the following. (1) The USAN exhibits scale-free, small-world and disassortative mixing properties, which are consistent with the mainstream perspectives. Besides, we find (2) a remarkable power relationship between the structural measurements in the binary graph and the traffic measurements in the weighted counterpart, namely degree versus capacity and attraction versus volume. On the other hand, investigation of the airport patterns suggests (3) that all the airports can be classified into four categories based on multiple network metrics, which shows a complete typology of the airports. And it further indicates (4) that there is a subtle relationship between the airport traffic and the geographical constraints as well as the regional socioeconomic indicators. 相似文献
239.
Yifang Ouyang Xiaofeng Tong Chang Li Hongmei Chen Xiaoma Tao Tilmann Hickel Yong Du 《Physica B: Condensed Matter》2012,407(23):4530-4536
With this work we present a newly developed potential for the Fe–Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D03-Fe3Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D03-Fe3Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe–Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe–Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe–Al system. 相似文献
240.
Accumulation-type GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic-layer-deposited Al2O3 gate dielectrics are fabricated. The device, with atomic-layer-deposited Al2O3 as the gate dielectric, presents a drain current of 260 mA/mm and a broad maximum transconductance of 34 mS/mm, which are better than those reported previously with Al2O3 as the gate dielectric. Furthermore, the device shows negligible current collapse in a wide range of bias voltages, owing to the effective passivation of the GaN surface by the Al2O3 film. The gate drain breakdown voltage is found to be about 59.5 V, and in addition the channel mobility of the n-GaN layer is about 380 cm2/Vs, which is consistent with the Hall result, and it is not degraded by atomic-layer-deposition Al2O3 growth and device fabrication. 相似文献