棒状纳米纤维素仿生矿化及光谱分析

以棒状纳米纤维素为模板,采用仿生矿化的方法制备纳米纤维素/纳米羟基磷灰石复合材料。并利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电镜能谱分析(SEM-EDAX)对仿生矿化前后纳米纤维素中碳、氧、钙、磷元素的变化情况及分布状态进行了表征,并探讨了纳米羟基磷灰石的生长机理。结果表明纳米纤维素表面形成了纳米羟基磷灰石;纳米纤维素的碳氧比为1.81,仿生矿化后下降为1.54;仿生矿化后纳米纤维素的钙磷比nCa/nP=1.70;纳米羟基磷灰石成核是在纳米纤维素的羟基上,并且纳米纤维素表面羟基和纳米羟基磷灰石的钙离子之间发生了配位作用。纳米羟基磷灰石较为均一的形成在纳米纤维素的基体中。通过原子力显微镜(AFM)图片可以看出,直径为20nm左右的羟基磷灰石生长在纳米纤维素的表面。     

Controllable switching behavior of optical Tamm state based on nematic liquid crystal

The controllable behavior of optical Tamm state (OTS) is investigated in a heterostructure with nematic liquid crystal (NLC). By changing the external fields (electric field and temperature), the orientation of NLC’s molecules can be modified. It offers us an effective way to control the optical properties of the optical Tamm state. We obtain the critical condition for the appearance of the optical Tamm state. Our theoretical analysis and numerical simulations show that through choosing appropriate parameters we can not only change the frequency position of the optical Tamm state, but also realize the disappearance of the OTS.     

Novel titration method for surface-functionalised silica

This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH₂-, SO₃H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.     

Conversion efficiency enhanced photovoltaic device with nanohole arrays in antireflection coating layer

In this paper, the authors introduce an enhanced photovoltaic device with nanohole arrays only in its antireflection coating. These nanoholes can improve light trapping efficiency as well as photoelectric conversion efficiency of the device. The authors analyze the light absorption of the devices with nanohole arrays by Finite-Difference Time Domain method and calculate the photoelectric conversion efficiency. The results show that the nanohole arrays can improve the light trapping more efficiently than the Si₃N₄ antireflection coating, especially, in 400-600 nm spectral range. Nanohole arrays with different characteristic parameters were fabricated in the antireflection coating layer of a Φ200 μm Si detector by using focused-ion beam system. With the optimized nanohole arrays, the enhancements factor of the experimental sample's photoelectric conversion efficiency is ~ 16% within the 400-600 nm spectral range and ~ 10% within the 400-1100 nm spectral range.     

Surface resonant-states-enhanced acoustic wave tunneling in two-dimensional phononic crystals

We show that by placing a metal plate next to a two-dimensional phononic crystal, acoustic waves can tunnel through the combined structure at a specific frequency that lies inside the band gap of the phononic crystal. The enhanced transmission is attributed to the coupling of the input waves with the acoustically resonant states created between the metal plate and the phononic crystal. Experiments are in excellent agreement with the theoretical predictions.     

A Conceptual Model of Somali Jet Based on the Biot--Savart Law

We study the relationship between thermal conditions on the earth bottom boundary and the formation of Somali jet based on the Biot-Savart law and the data from National Centres for Environmental Prediction （NCEP）. As the radiation from the Sun gradually moves from the southern meridian, the temperature on the surface of Somali Peninsular and Arabic Peninsular gradually increases. During the same period the surface temperature of the Northern Indian Ocean increases much slower. It is shown that this increase of the temperature difference between the land and sea is inductive to the formation and development of Rayleigh-Benard convection and leads to the increasing relative vorticity strength between positive and negative vertical vortices over the land and sea. According to the Biot-Savart law, increase of vorticity strength will correspondingly induce the horizontal velocity. A pair of positive and negative vorticity fields over the two Peninsulars and the sea surface is effective in forming and maintaining this current. This mechanism is referred to as the ＇Somali suction pump＇. It draws air continually from the Southern hemisphere and releases it at the coastal area of Somali.     

Long period grating cascaded to photonic crystal fiber modal interferometer for simultaneous measurement of temperature and refractive index

We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment.     

结合小波分析法与导数光声光谱技术测量弱光谱信号的实验研究

结合导数光声光谱技术与小波分析方法,精确测量了光声光谱中的弱光谱信号.首先利用自己设计的仪器装置实现光声光谱的一阶导数,在此基础上,根据导数光声光谱的数据选择合理的分析小波,将光声光谱信号分解为不同频率信号的叠加,被分解的信号满足线性性质且原信号的峰值信息保持不变,由频率的差异可区分出光声信号和噪声信号,从而提取出光声光谱中的弱光谱信号.结合物理方法与软件方法的分析结果,准确地测量了氙灯的输出光声光谱中3个不明显的弱峰值,位置分别为699.7nm、753.4nm和776.5nm.该方法可以更准确地提取出光声光谱的峰值信息,有效地提高了光声光谱的测量精度,为光声光谱分析法在生物医学及化学分析中的应用提供了一种更精确的分析方法.     

Nonclassicality and Decoherence of Photon-added Thermo-invariant Coherent State

By introducing a kind of new quantum state—Photon-added thermo invariant coherent state (PATCS), we discuss its nonclassicality in terms of the negativity of Wigner function (WF) after deriving its analytical expression. It is found that the Wigner function is related to Lagurre-Gaussian function. We then study the effect of decoherence (a thermal environment) on the PATCS according to its WF (also related to Lagurre-Gaussian function). It is shown that it is not possible for WF to present the negative region when the decay time $\kappa t>\frac{1}{2}\ln \frac{2\bar{n}+2}{2\bar{n}+1}$\kappa t>\frac{1}{2}\ln \frac{2\bar{n}+2}{2\bar{n}+1} .     

Layered lithium-rich oxide nanoparticles: low-temperature synthesis in mixed molten salt and excellent performance as cathode of lithium-ion battery

Layered lithium-rich oxide, 0.5Li₂MnO₃·0.5LiMn_1/3Ni_1/3Co_1/3O₂, is synthesized in a mixed molten salt of KCl and LiCl under 750 °C. Its morphology and structure are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption and desorption isotherm, and its performances as cathode of lithium-ion battery are investigated by charge–discharge test and electrochemical impedance spectroscopy, with a comparison of the samples synthesized via solid-state reaction. It is found that the resulting product consists of uniform nanoparticles, 50 nm in average, which possesses a well crystallite layered structure although its synthesis temperature is low and thus exhibits excellent cyclic stability and rate capability. The resulting product delivers an initial discharge capacity of 268 mAh g^?1 at 0.1 C and has a capacity retention of 82% after 100 cycles at 1 C, compared to the 243 mAh g^?1 and 73% for the sample synthesized by solid-state reaction under 900 °C.