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71.
Huiliang Xu Zeyu Zhao Yueguang Lv Chunlei Du Xiangang Luo 《International Journal of Infrared and Millimeter Waves》2008,29(5):493-498
A high directive planar antenna made from a metamaterial superstrate and an electromagnetic band-gap (EBG) substrate has been
investigated. A patch antenna surrounded with EBG structures is used as the radiation source. The CST Microwave Studio is
used for the simulation. The results show that the gain of the antenna with metamaterial is 21.6 dB at the operating frequency
of 14.6 GHz. Compared with the patch feed with the same aperture size but without the metamaterial superstrate, the performance
of the antenna is improved obviously and the gain increases about 12.4 dB. 相似文献
72.
There is a natural tendency in science to prefer straightforward, logical classification systems. The use of mobile phase-stationary phase combinations that do not fit neatly into the standard "normal phase" or "reversed-phase" categories has been going on for over 50 years. The term "hydrophilic interaction chromatography" (HILIC) is sometimes being used as a general category for these "other" separations. In some cases, it may be appropriate and in others, not. Indeed the mechanistic constrains used to define the method seem to be varying with time. Given the name HILIC, it is assumed that water is not only present in the mobile phase, but also plays an essential role in the retention mechanism. However, there is residual water present in all organic solvents. Regardless, the number of reported separations in this alternative mode has increased tremendously in the last two decades. This is due to the advent of new stationary phases and an emphasis on polar, biologically important molecules. We discuss the relationships between HILIC and other chromatographic modes. We then examine two classes of stationary phases that have played a major role in these separations. These particular stationary phases can be used to provide appreciable mechanistic information as well. 相似文献
73.
Bing Yang Dr. Soo‐Kang Kim Hai Xu Young‐Il Park Houyu Zhang Dr. Cheng Gu Fangzhong Shen Dr. Chunlei Wang Dandan Liu Xiaodong Liu Prof. Muddasir Hanif Shi Tang Weijun Li Feng Li Dr. Jiacong Shen Prof. Jong‐Wook Park Prof. Yuguang Ma Prof. 《Chemphyschem》2008,9(17):2601-2609
Herein, we describe the molecular electronic structure, optical, and charge‐transport properties of anthracene derivatives computationally using density functional theory to understand the factors responsible for the improved efficiency and stability of organic light‐emitting diodes (OLEDs) with triphenylamine (TPA)‐substituted anthracene derivatives. The high performance of OLEDs with TPA‐substituted anthracene is revealed to derive from three original features in comparison with aryl‐substituted anthracene derivatives: 1) the HOMO and LUMO are localized separately on TPA and anthracene moieties, respectively, which leads to better stability of the OLEDs due to the more stable cation of TPA under a hole majority‐carrier environment; 2) the more balanceable hole and electron transport together with the easier hole injection leads to a larger rate of hole–electron recombination, which corresponds to the higher electroluminescence efficiency; and 3) the increasing reorganization energy for both hole and electron transport and the higher HOMO energy level provide a stable potential well for hole trapping, and then trapped holes induce a built‐in electric field to prompt the balance of charge‐carrier injection. 相似文献
74.
Chunlei Li Andrew M. Kiss Douglas G. Van Campen Alex Garachtchenko Yuriy Kolotovsky Kevin Stone Yahong Xu Wenjun Zhang Jeff Corbett 《Journal of synchrotron radiation》2016,23(4):909-918
Typical X‐ray diffraction measurements are made by moving a detector to discrete positions in space and then measuring the signal at each stationary position. This step‐scanning method can be time‐consuming, and may induce vibrations in the measurement system when the motors are accelerated and decelerated at each position. Furthermore, diffraction information between the data points may be missed unless a fine step‐scanning is used, which further increases the total measurement time. To utilize beam time efficiently, the motor acceleration and deceleration time should be minimized, and the signal‐to‐noise ratio should be maximized. To accomplish this, an integrated continuous‐scan system was developed at the Stanford Synchrotron Radiation Lightsource (SSRL). The continuous‐scan system uses an in‐house integrated motor controller system and counter/timer electronics. SPEC software is used to control both the hardware and data acquisition systems. The time efficiency and repeatability of the continuous‐scan system were tested using X‐ray diffraction from a ZnO powder and compared with the step‐scan technique. Advantages and limitations of the continuous‐scan system and a demonstration of variable‐velocity continuous scan are discussed. 相似文献
75.
Micropatterning of the Ferroelectric Phase in a Poly(vinylidene difluoride) Film by Plasmonic Heating with Gold Nanocages 下载免费PDF全文
Jianhua Li Miaoxin Yang Xiaojun Sun Dr. Xuan Yang Dr. JiaJia Xue Dr. Chunlei Zhu Prof. Hong Liu Prof. Younan Xia 《Angewandte Chemie (International ed. in English)》2016,55(44):13828-13832
Polymer thin films with patterned ferroelectric domains are attractive for a broad range of applications, including the fabrication of tactile sensors, infrared detectors, and non‐volatile memories. Herein, we report the use of gold nanocages (AuNCs) as plasmonic nanostructures to induce a ferroelectric–paraelectric phase transition in a poly(vinylidene fluoride) (PVDF) thin film by leveraging its photothermal effect. This technique allows us to generate patterned domains of ferroelectric PVDF within just a few seconds. The incorporation of AuNCs significantly enhances the pyroelectric response of the ferroelectric film under near‐infrared irradiation. We also demonstrate the use of such patterned ferroelectric films for near‐infrared sensing/imaging. 相似文献
76.
77.
A double-well potential model is established to explain the dielectric anomaly of ferroelectrics. The dielectric constant
consists of two parts. One part is independent of the long-range correlation, following 1/T law. The other part originates
from the long-range correlation, and can be described by the correlation length well. The deviation from Curie-Weiss law in
a small size sample originates from the decrease of the long-range correlation.
Project supported by the Climbing Program of Foundamental Research of China. 相似文献
78.
Combining two methods, coating and doping, to modify spinel LiMn2O4, is a novel approach we used to synthesize active material. First we coated the LiMn2O4 particles with the nickel oxide particles by means of homogenous precipitation, and then the nickel oxide-coated LiMn2O4 was calcined at 750 °C to form a LiNixMn2−xO4 shell on the surface of spinel LiMn2O4 particles. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cyclic voltammetry (CV) and charge-discharge test were performed to characterize the spinel LiMn2O4 before and after modification. The experimental results indicated that a spinel LiMn2O4 core is surrounded by a LiNixMn2−xO4 shell. The resulting composite showed excellent electrochemical cycling performance with an average fading rate of 0.014% per cycle. This improved cycle stability is greatly attributed to the suppression of Jahn-Teller distortion on the surface of spinel LiMn2O4 particles during cycling. 相似文献
79.
Liyuan Liu Haofei Shi Xiangang Luo Xingzhan Wei Chunlei Du 《Applied Physics A: Materials Science & Processing》2009,95(2):563-566
Considering the fact that just the electrons confined in the region of the skin depth will actually affect the plasma frequency
due to the skin effect, a model for constructing epsilon-near-zero (ENZ) metamaterials through the arranged thin metallic
wires with arbitrary cross-section is developed, utilizing the perimeter approximation. With our model, plasma frequency can
be freely modulated just by the variance of the metallic wire perimeter, irrespective of the cross-section shape of wires.
The finite element method (FEM) and S-parameters retrieval method were employed to numerically simulate the plasma frequencies,
which have verified the validity of the theoretical model. 相似文献
80.
The time evolution of the entanglement of a pair of two spin qubits is investigated when the two qubits simultaneously couple to an environment of an anisotropic Heisenberg XXZ spin chain. The entanglement of the two spin qubits can be created and is a periodic function of the time if the magnetic field is greater than a critical value. If the two spin qubits are in the Bell state, the entanglement can be stored with relatively large value even when the magnetic field is large. 相似文献