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181.
We experimentally demonstrate a diode-pumped passively mode-locked femtosecond laser with Yb 3+ -doped yttrium lanthanum oxide ceramic. Mode-locking is achieved by using a semiconductor saturable absorber mirror, and intracavity dispersion is compensated by a pair of SF6 prisms. Laser pulses as short as 357 fs at a central wavelength of 1 075 nm are obtained. The maximum average output power is 670 mW under 4.5 W of pumping power with a slope efficiency of 20%. To the best of our knowledge, this is the shortest pulse generated from Yb-doped yttrium lanthanum oxide ceramic lasers with a sub-500 fs pulse duration. 相似文献
182.
In this work, we study the evolution of a Gaussian beam inside a one-dimensional inverted nonlinear photonic crystals (INPC) with a Kerr nonlinearity. The INPC is a kind of virtual crystals which is generated by the optical induction via the electromagnetically induced transparency (EIT). The propagation dynamics of the Gaussian with different total power are identified. Four types of propagation behavior are found. They are collapse beam, breather beam, soliton and symmetry-breaking beam, respectively. The border between these four behavior types are given. For symmetry-breaking beam, an asymmetric profile of the beam is evolving from the symmetry Gaussian, which can be termed as a kind of dynamical symmetry breaking (DSB). The influences on the appearance of the symmetry breaking point are studied by varying input parameters of the Gaussian. The results of this work are both suitable in nonlinear optics and Bose-Einstein condensate (BEC). 相似文献
183.
184.
Haiqing XiaBin Cui Junhong ZhouLulu Zhang Ji ZhangXiaohui Guo Huilin Guo 《Applied Surface Science》2011,257(22):9397-9402
We synthesized Fe3O4@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe3O4@Ag nanocomposites, the Fe3O4@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe3O4@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10 μg/mL. Antibacterial activity of the Fe3O4@C@Ag nanocomposites was maintained for more than 40 h at 37 °C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe3O4@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic-optical materials. 相似文献
185.
This paper discusses the identification problems of Hammerstein controlled autoregressive autoregressive (CARAR) systems using the maximum likelihood principle and Newton optimization method. A Newton recursive algorithm and a Newton iterative algorithm using the maximum likelihood principle are presented. The simulation results show that the proposed algorithms can effectively estimate the parameters of the Hammerstein CARAR systems. 相似文献
186.
Xiaoliang Zhang Yongjuan Lu Xiaohua Zhong Gewen Yi Junhong Jia 《Surface and interface analysis : SIA》2012,44(1):126-132
Surface roughness plays an important role in affecting the adhesive force and friction force in microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS). One effective approach of reducing adhesion and friction of contacting interfaces is to create textured surface, which is especially beneficial for MEMS'/NEMS' production yield and product reliability. In this article, we present a convenient method to fabricate the nano‐textured surfaces by self‐assembling Au nanoparticles (NPs) on the silicon (100) surfaces. The nanoparticle‐textured surfaces (NPTS) with different packing density and texture height were prepared by controlling the assembling time and the size of Au NPs. The morphologies and chemical states of NPTS were characterized by atomic force microscope (AFM), field emission scanning electron microscope, and XPS. The adhesion and friction on the NPTS were studied by AFM with colloidal tip. The results show that the nano‐textured surfaces have effectively reduced adhesive force and friction force compared with the 3‐aminopropyl trimethoxysilane self‐assembled monolayer surfaces. The lowered adhesion and friction were attributed to the reduced real area of contact between NPTS and colloidal tip. The adhesion and friction of the NPTS are varying with the texture packing density and dependent on both the texture height and asperities spacing, which are related to the size and coverage ratio of NPs on surfaces. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
187.
188.
Kaiqing Luo Junhong Jin Shenglin Yang Jianming Jiang 《Journal of Macromolecular Science: Physics》2013,52(4):631-637
In order to improve surface properties of poly (p‐phenylene benzoxazole) (PBO) fiber, modified SPBO containing ionic groups (–NaSO3) was prepared for the first time by polymerization from 1, 3‐diamino‐4, 6‐dihydroxybenzene dihydrochloride (DAR) and terephthalic acid (TPA), with addition of selected amounts of 5‐sulfoisophthalic acid monosodium salt (SIPA) in place of the TPA. The SPBO polymer with a different content of SIPA, 1.5% SPBO (mol ratio), and 3% SPBO was prepared. The SPBO fiber was obtained via liquid crystal spinning through dry‐jet wet‐spinning techniques. The contact angles between fiber and water/ethyl alcohol were measured by an OCA 40 Micro dynamic contact angle analysis system. The contact angles of SPBO to water and alcohol were smaller than those of PBO to either of them and the wetting process of water and ethyl alcohol on SPBO fiber was faster than on PBO fiber. In addition, the results showed that the surface free energy could be increased up to 40.3 mJ/m2, i.e. by 13.55%. Through XPS analysis, it was found that the surface nitrogen‐to‐carbon ratio was increased from 0.0157 to 0.0915 and the oxygen‐to‐carbon ratio was increased from 0.2331 to 0.3070 after incorporation of the ‐NaSO3 ionic groups; in addition, the ionization energy (or binding energy) of C1s and O1s decreased. 相似文献
189.
Tao Zhang Junhong Jin Shenglin Yang Dayong Hu Guang Li Jianming Jiang 《Journal of Macromolecular Science: Physics》2013,52(6):1114-1124
A series of novel fluorinated benzoxazole polymers (6FPBO) with high thermal stability and low dielectric constant were synthesized by copolymerization of 1,3-diamino-4, 6-dihydroxybenzene dihydrochloride (DAR), purified terephthalic acid (PTA) and various amount of 4′4-(hexafluoroisopropylidene) bis(benzoic acid) (BIS-B-AF) in the medium of polyphosphoric acid (PPA). 6FPBO fibers were then obtained via dry-jet wet-spinning technique and characterized by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), broadband dielectric spectrometer, single fiber tensile testing machine, and scanning electron microscopy (SEM). The FTIR spectrum of 6FPBO fibers indicated that the fluorine groups were incorporated into PBO molecular chains successfully. TGA curves revealed that 6FPBO fibers possessed high thermal stability, just as pure PBO fibers. Moreover, the dielectric constant spectra of 6FPBO showed that the polymers had low dielectric constant, especially in the range of high-frequency. 相似文献
190.
Lulu Huang Saeed Ahmed Yufeng Gu Junhong Huang Boyu An Cuirong Wu Yujie Zhou Guyue Cheng 《Molecules (Basel, Switzerland)》2021,26(14)
Due to the extensive application of antibiotics in medical and farming practices, the continued diversification and development of antimicrobial resistance (AMR) has attracted serious public concern. With the emergence of AMR and the failure to treat bacterial infections, it has led to an increased interest in searching for novel antibacterial substances such as natural antimicrobial substances, including microbial volatile compounds (MVCs), plant-derived compounds, and antimicrobial peptides. However, increasing observations have revealed that AMR is associated not only with the use of antibacterial substances but also with tolerance to heavy metals existing in nature and being used in agriculture practice. Additionally, bacteria respond to environmental stresses, e.g., nutrients, oxidative stress, envelope stress, by employing various adaptive strategies that contribute to the development of AMR and the survival of bacteria. Therefore, we need to elucidate thoroughly the factors and conditions affecting AMR to take comprehensive measures to control the development of AMR. 相似文献