Tribological properties of diamond-like carbon films deposited by pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon (DLC) nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp$^{2}$, sp$^{3}$ and C--O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17--21~nm, 30--57~nm, 67--123~nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17--41~nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123~nm.     

Phased array focusing with guided waves in a viscoelastic coated hollow cylinder

Guided wave phased array focusing has shown many advantages in long-range pipeline inspection, such as, longer inspection distance, greater wave penetration power and higher detection resolution. Viscoelastic coatings applied to a large percentage of pipes for protection purposes created some challenges in terms of focusing feasibility and inspection ability. Previous studies were all based on bare pipe models. In this work, guided wave phased array focusing in viscoelastic coated pipes is studied for the first time. Work was carried out with both numerical and experimental methods. A three-dimensional finite element model was developed for quantitatively and systematically modeling guided waves in pipes with different viscoelastic materials. A method of transforming measured coating properties to finite element method inputs was created in order to create a physically based model of guided waves in coated pipes. Guided wave focusing possibilities in viscoelastic coated pipes and the effects from coatings were comprehensively studied afterwards. A comparison of focusing and nonfocusing inspections was also studied quantitatively in coated pipe showing that focusing increased the wave energy and consequently the inspection ability tremendously. This study provides an important base line and guidance for guided wave propagation and focusing in a real field pipeline under various coating and environmental conditions.     

Highly stable amorphous indium‐zinc‐oxide thin‐film transistors with back‐channel wet‐etch process

The stabilities of amorphous indium‐zinc‐oxide (IZO) thin film transistors (TFTs) with back‐channel‐etch (BCE) structure are investigated. A molybdenum (Mo) source/drain electrode was deposited on an IZO layer and patterned by hydrogen peroxide (H₂O₂)‐based etchants. Then, after etching the Mo layer, SF₆ plasma with direct plasma mode was employed and optimized to improve the bias stress stability. Scanning electron microscopy and X‐ray photoelectron spectroscopic analysis revealed that the etching residues were removed efficiently by the plasma treatment. The modified BCE‐ TFTs showed only threshold voltage shifts of 0.25 V and –0.20 V under positive/negative bias thermal stress (P/NBTS, V_GS = ±30 V, V_DS = 0 V and T = 60 °C) after 12 hours, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

对旋轴流风机反风性能的数值模拟

本文对一种对旋式轴流风机,采用SIMPLE方法对其整机的正、反风性能进行预测,通过求解雷诺平均N-S方程,湍流模型采用标准的k-ε模型,给出了分析采用的几何模型,通过CFD分析,预测出对旋式轴流风机的反风性能.通过对正风、反风预测性能的比较,结果表明:正风时的内流明显优于反风,主要内流细节差异是由于反风时流道收缩导致,反风时两级叶轮的负荷分配不均衡,后级叶轮负荷约为一级叶轮负荷的两倍多.对旋式轴流风机在反风运行状态下,流量、压力、功率各项参数的值均小于正风运行状态下的值,但其相对于普通轴流风机具有较大的反风量,反风量能达到正常风量的65%以上,可以满足对风机反风量的安全要求.     

New side-pump scheme for large mode area fiber lasers by wrapping polished fibers conjugate caustic removed

With the purpose of uniform gain coefficient along the axial direction in the core of gain guided and index anti-guided fiber, a new kind of side-pump scheme by wrapping particularly treated fibers around the central GGIAG fiber is reported in this paper. According to leakage mode analysis on wrapped fiber and numerical simulation on this pumping structure having ytterbium doped central fiber and conventional wrapped side fiber, we find this kind of pump scheme can improve the uniformity of gain coefficient along the fiber direction, and also, it can support multi channels of pumping sources by adding more side fibers to improve the total effective incident pumping power.     

Stability Analysis of a Fully Coupled Implicit Scheme for Inviscid Chemical Non-Equilibrium Flows

Von Neumann stability theory is applied to analyze the stability of a fully coupled implicit (FCI) scheme based on the lower-upper symmetric Gauss-Seidel (LU-SGS) method for inviscid chemical non-equilibrium flows. The FCI scheme shows excellent stability except the case of the flows involving strong recombination reactions, and can weaken or even eliminate the instability resulting from the stiffness problem, which occurs in the subsonic high-temperature region of the hypersonic flow field. In addition, when the full Jacobian of chemical source term is diagonalized, the stability of the FCI scheme relies heavily on the flow conditions. Especially in the case of high temperature and subsonic state, the CFL number satisfying the stability is very small. Moreover, we also consider the effect of the space step, and demonstrate that the stability of the FCI scheme with the diagonalized Jacobian can be improved by reducing the space step. Therefore, we propose an improved method on the grid distribution according to the flow conditions. Numerical tests validate sufficiently the foregoing analyses. Based on the improved grid, the CFL number can be quickly ramped up to large values for convergence acceleration.     

A theoretical study of the oxygen K-edge near-edge X-ray absorption ne structure of N2O/Ir(110)

A multiple-scattering cluster method is employed to calculate the oxygen K-edge near-edge X-ray absorption fine structure of N₂O/Ir(110) and its monolayer. Two peaks and one weak resonance appear in both cases. The selfconsistent field DV-X calculations of the peaks and resonance show that the physical origin of the pre-edge peak x is different from those of the main peak 1 and the other weak resonance σ₁. This setup is intrinsic to the N₂O monolayer, owing to the interaction between the neighbouring molecular chains in the monolayer and partly to the adsorbed atomic oxygen, according to both the theoretical and experimental data.     

HT-7托卡马克slide-away放电充气对等离子体行为的影响

本文研究了slide-away放电条件下的等离子体约束性能;分析了充气对等离子体约束性能以及反常多普勒共振不稳定性的影响.研究了等离子体密度的提升对slide-away放电过程中逃逸电子辐射行为的影响.研究结果发现:slide-away放电充气可以抑制逃逸电子反常多普勒不稳定性,但是使得等离子体约束状态变差,逃逸电子辐射增强.     

中、远红外双波段激光器发射光谱测量与评估

在分析中远红外双波段(氟化氘与一氧化碳)激光器发射光谱的基本特征和分光型谱仪存在高级次光谱混叠等问题的基础上,选定Tensor37干涉型遥测光谱仪并利用黑体标定出仪器响应函数;对中、远红外双波段激光器光谱进行了模拟测量和实际测量,分析评估了双波段激光器的谱线成分、峰值变化、测量精度和相对强度等,为双波段激光器的介质参数计算、运转参数优化以及红外应用提供有效数据。     

基于小波变换的体内外酒精含量近红外光谱检测与分析

应用小波分析对体外和体内的酒精近红外光谱信号进行去噪分析,通过体外光谱分析确定酒精吸收峰特征范围,为体内近红外光谱分析确定有效区间。软阈值和硬阈值下,分别采用缺省阈值、Birge-Massart阈值和最大最小值阈值,比较酒精光谱去噪,信噪比(signal noise ratio,SNR)和均方根误差(root mean square error,RMSE)去噪效果。结果表明:缺省硬阈值方法对酒精近红外光谱去噪的效果较好;小波变换可以有效去除酒精近红外光谱的噪声,提高信噪比,保留有用真实信号。在不同的酒精浓度下,去噪后的近红外光谱能够较好的显示浓度变化规律。小波分析在近红外光谱法对人体酒精无创检测及定量分析方面有较好的应用前景。