Density and impurity profile behaviours in HL-2A tokamak with different gas fuelling methods

The electron density profile peaking and the impurity accumulation in the HL-2A tokamak plasma are observed when three kinds of fuelling methods are separately used at different fuelling particle locations. The density profile becomes more peaked when the line-averaged electron density approaches the Greenwald density limit n_G and, consequently, impurity accumulation is often observed. A linear increase regime in the density range n_e< 0.6n_G and a saturation regime in n_e > 0.6n_G are obtained. There is no significant difference in achieved density peaking factor f_ne between the supersonic molecular beam injection (SMBI) and gas puffing into the plasma main chamber. However, the achieved f_ne is relatively low, in particular, in the case of density below 0.7n_G, when the working gas is puffed into the divertor chamber. A discharge with a density as high as 1.2n_G, i.e. n_e = 1.2n_G, can be achieved by SMBI just after siliconization as a wall conditioning. The metallic impurities, such as iron and chromium, also increase remarkably when the impurity accumulation happens. The mechanism behind the density peaking and impurity accumulation is studied by investigating both the density peaking factor versus the effective collisionality and the radiation peaking versus density peaking.     

A Fast Approach to Removing Muscle Artifacts for EEG with Signal Serialization Based Ensemble Empirical Mode Decomposition

An electroencephalogram (EEG) is an electrophysiological signal reflecting the functional state of the brain. As the control signal of the brain–computer interface (BCI), EEG may build a bridge between humans and computers to improve the life quality for patients with movement disorders. The collected EEG signals are extremely susceptible to the contamination of electromyography (EMG) artifacts, affecting their original characteristics. Therefore, EEG denoising is an essential preprocessing step in any BCI system. Previous studies have confirmed that the combination of ensemble empirical mode decomposition (EEMD) and canonical correlation analysis (CCA) can effectively suppress EMG artifacts. However, the time-consuming iterative process of EEMD may limit the application of the EEMD-CCA method in real-time monitoring of BCI. Compared with the existing EEMD, the recently proposed signal serialization based EEMD (sEEMD) is a good choice to provide effective signal analysis and fast mode decomposition. In this study, an EMG denoising method based on sEEMD and CCA is discussed. All of the analyses are carried out on semi-simulated data. The results show that, in terms of frequency and amplitude, the intrinsic mode functions (IMFs) decomposed by sEEMD are consistent with the IMFs obtained by EEMD. There is no significant difference in the ability to separate EMG artifacts from EEG signals between the sEEMD-CCA method and the EEMD-CCA method (p > 0.05). Even in the case of heavy contamination (signal-to-noise ratio is less than 2 dB), the relative root mean squared error is about 0.3, and the average correlation coefficient remains above 0.9. The running speed of the sEEMD-CCA method to remove EMG artifacts is significantly improved in comparison with that of EEMD-CCA method (p < 0.05). The running time of the sEEMD-CCA method for three lengths of semi-simulated data is shortened by more than 50%. This indicates that sEEMD-CCA is a promising tool for EMG artifact removal in real-time BCI systems.     

Ni nanoparticles encapsulated within H-type ZSM-5 crystals for upgrading palmitic acid to diesel-like fuels

Meso-Ni@HZSM-5 bi-functional catalysts were successfully post-encapsulated with about 3–7 nm Ni nanoparticles within HZSM-5 crystals,which exhibited significantly efficient conversion activity (67.4g[palmitic acid]g[Ni]^-1h^-1) of palmitic acid and 100%selectivity of hydrocarbons with the outstanding stability during recycling application,compared to the impregnated Ni/HZSM-5 catalyst (14.0 g[palmitic acid]g[Ni]^-1h^-1).     

傅里叶变换红外光谱用于胃镜样品的检测

应用傅里叶变换红外光谱(FTIR) 法对184例不同病理状态的胃镜下活检组织样品进行检测和分析,结果表明,慢性浅表性胃炎的基本谱图特征包括：较强的酰胺Ⅱ带;1 460 cm-1处的峰强高于1 400 cm-1处的峰强。典型的胃癌组织的谱图特征包括：较低的酰胺Ⅱ带;1 460 cm-1处的峰强低于1 400 cm-1处的峰强;1 300 cm-1的峰强明显增加。慢性萎缩性胃炎呈现出部分胃癌的光谱特征。这一结果表明,应用FTIR可以对胃镜下活检的小块组织进行鉴别诊断。     

Modulational instability of ion—acoustic waves in a warm plasma

Using the standard reductive perturbation technique,a nonlinear Schroedinger equation is derived to study the modulational instability of finite-amplitude ion-acoustic waves in a non-magnetized warm plasma.It is found that the inclusion of ion temperature in the equation modifies the nature of the ion-acoustic wave stability and the soliton stuctures.The effects of ion plasma temperature on the modulational stability and ion-acoustic wave properties are inestigated in detail.     

Dichloro(2,2′‐diamino‐4,4′‐bi‐1,3‐thiazole‐N3,N3′)copper(II)

The title complex, [CuCl₂(C₆H₆N₄S₂)], has a flattened tetrahedral coordination. The Cu^II atom is located on a twofold rotation axis and is coordinated by two N atoms from a chelating 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and by two Cl atoms. Intramolecular hydrogen bonding exists between the amino groups of the 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and the Cl atoms. The intermolecular separation of 3.425 (1) Å between parallel bi­thia­zole rings suggests there is a π–π interaction between them.     

霍尔推进器中磁化二次电子对鞘层特性的影响

为进一步研究霍尔推进器壁面二次电子发射对推进器性能的影响,采用流体模型数值模拟了二次电子磁化效应的等离子体鞘层特性.得到二次电子磁化鞘层的玻姆判据.讨论了不同的磁场强度和方向、二次电子发射系数以及不同种类等离子体推进器的鞘层结构.结果表明:随器壁二次电子发射系数的增大,鞘层中粒子密度增加,器壁电势升高,鞘层厚度减小;鞘层电势及粒子密度随着磁场强度和方位角的增加而增加;而对于不同种类的等离子体,壁面电势和鞘层厚度也不同.这为霍尔推进器的磁安特性实验提供了理论解释. 关键词： 霍尔推进器 磁鞘 二次电子     

黏滞等离子体中双撕裂模不稳定性的数值模拟研究

本文采用磁流体力学模型,数值研究了平板位形下双撕裂模线性增长率关于等离子体电阻η和黏滞v的定标关系.结果表明,对于有理面间距较大的情况,线性增长率关于电阻和黏滞的指数定标率随着黏滞的增加逐渐由γ∝ η3/5v0的定标变化到γ∝η5/6v-1/6的定标;而对于有理面间距较小的情况,其指数定标率随着黏性的增加从γ∝η 1/3 v0的定标逐渐变化到γ∝η2/3v-1/3的定标.本文还给出了初始阶段对称的双撕裂模的非线性演化,发现在非线性阶段对称的双撕裂模将转化为反对称的双撕裂模,并解释了相应的物理机理.     

Judd--Ofelt analysis of spectra and experimental evaluation of laser performance of Tm3+ doped Lu2SiO5 crystal

This paper reports that the Tm^3＋：Lu2SiO5 （Tm：LSO） crystal is grown by Czochralski technique. The roomtemperature absorption spectra of Tm：LSO crystal are measured on a b-cut sample with 4 at.% thulium. According to the obtained Judd-Ofelt intensity parameters Ω2=9.3155×10^-20 cm^2, Ω4=8.4103×10^-20 cm^2, Ω6=1.5908×10^-20 cm^2, the fluorescence lifetime is calculated to be 2.03 ms for ^3F4 → ^3H6 transition, and the integrated emission cross section is 5.81×10^-18 cm^2. Room-temperature laser action near 2μm under diode pumping is experimentally evaluated in Tm：LSO. An optical-optical conversion efficiency of 9.1% and a slope efficiency of 16.2% are obtained with continuouswave maximum output power of 0.67 W. The emission wavelengths of Tm：LSO laser are centred around 2.06μm with spectral bandwidth of -13.6 nm.     

Cations Modulated Assembly of Triol-Ligand Modified Cu-Centered Anderson-Evans Polyanions

Counter-cations are essential components of polyoxometalates (POMs), which have a distinct influence on the solubility, stabilization, self-assembly, and functionality of POMs. To investigate the roles of cations in the packing of POMs, as a systematic investigation, herein, a series of triol-ligand covalently modified Cu-centered Anderson-Evans POMs with different counter ions were prepared in an aqueous solution and characterized by various techniques including single-crystal X-ray diffraction. Using the strategy of controlling Mo sources, in the presence of triol ligand, NH₄⁺, Cu²⁺ and Na⁺ were introduced successfully into POMs. When (NH₄)₆Mo₇O₂₄ was selected, the counter cations of the produced POMs were ammonium ions, which resulted in the existence of clusters in the discrete state. Additionally, with the modulation of the pH of the solutions, the modified sites of triol ligands on the cluster can be controlled to form δ- or χ-isomers. By applying MoO₃ in the same reaction, Cu²⁺ ions served as linkers to connect triol-ligand modified polyanions into chains. When Na₄Mo₈O₂₆ was employed as the Mo source to react with triol ligands in the presence of CuCl₂, two 2-D networks were obtained with {Na₄(H₂O)₁₄} or {{Na₂(H₂O)₄} sub-clusters as linkers, where the building blocks were δ/δ- and χ/χ-isomers, respectively. The present investigation reveals that the charges, sizes and coordination manners of the counter cations have an obvious influence on the assembled structure of polyanions.