MPCVD类金刚石膜抗氧化和摩擦性能的研究

目的研究MPCVD法制备的DLC膜的抗氧化和摩擦性能。方法使用石英钟罩式MPCVD装置,在CH4-H2体系中,通过不同微波功率和沉积气压的正交实验,在载玻片上沉积DLC膜。通过X射线光电子能谱和拉曼光谱对DLC膜表面的化学组成进行测试分析,采用场发射扫描电镜对DLC膜的表面形貌进行观察分析,采用摩擦磨损仪对DLC膜的摩擦性能进行测试研究。结果同一沉积气压下,IO1s/IC1s和sp2/sp3的比值随着微波功率的上升而下降;同一微波功率下,IO1s/IC1s和sp2/sp3的比值随着沉积气压的上升而上升。DLC膜的抗氧化性能随着sp2/sp3比值的下降而上升。场发射扫描电镜结果表明,微波功率由500 W上升至700 W时,DLC膜表面的团聚现象明显受到抑制,摩擦系数下降。当微波功率上升至900 W时,DLC膜表面出现明显裂痕,摩擦系数上升。微波功率为700 W、沉积气压为8.0 k Pa时,可得到氧化性能较好、摩擦系数最低为0.14的DLC膜。结论 MPCVD法制备的DLC膜的抗氧化性能受sp2/sp3比值的影响,比值越低,抗氧化性能越好。摩擦性能同时受sp2/sp3比值和其表面粗糙度的影响,比值越小,表面越平整,摩擦系数越小。     

秸秆中木质素对其超低酸水解过程的影响

以湖北稻草秸秆为研究对象,研究了超低酸水解木质纤维素的适宜条件,测定了适宜条件下的超低酸法水解15种不同种类秸秆的纤维素及半纤维素的转化率、还原糖得率及结晶度的变化。实验结果表明:秸秆投料量3 g、硫酸投料量45 mL(硫酸质量分数0.05%)、搅拌转速500 r/min、反应温度210 ℃、反应时间10 min为适宜的水解条件。对15种不同种类秸秆的水解结果统计得到,随着秸秆中木质素含量的增大,纤维素和半纤维素的转化率都逐渐降低,还原糖得率逐渐降低;通过SEM和X衍射分析水解前后的木质纤维素结构,得到了木质素影响水解过程的方式:1)木质素含量越大,纤维素的结晶度越大,纤维素的非晶化越困难,从而影响了纤维素的水解;2)原木质素不溶于反应体系且在酸性条件下相对稳定,富木质素层的木质素阻碍反应物与产物扩散,使富木质素层内的纤维素、半纤维素水解速率降低;3)木质素含量越高,木质纤维素的富木质素层越厚、强度越大,水解时难以从颗粒表面脱落,进一步降低水解速率。     

Extrusion de supports de catalyseurs : Le problème de la caractérisation rhéologique des pâtes fortement chargées

Catalysts support extrusion: the problem of rheological characterization of high concentrated mineral pastes. To exhibit a large specific surface (up to several hundred square meter per gram), catalysts are often porous materials. Their manufacturing involves a powder forming process. This process is achieved in several steps: (i) mixing a powder with an aqueous or polymeric binder to form a paste, (ii) extruding the paste to form the product, (iii) drying it and finally (iv) slightly sintering it. The paste which is studied in this paper is made of titanium oxide and aqueous acidic binder (nitric acid). The role of the acid is to disperse “at best” the T _i O ₂ powder by colloidal action. This kind of manufacturing process is old but remains however difficult to control because of many different difficulties: e.g., dies design, the balancing of several hole paths and more generally explicit what could be a “paste extrudability”. In this paper, first, we show experimentally that this type of material can present a heterogeneity induced by its flow. Second, we propose a modelization of the behavior of this product in the framework of the mixture theory. Third, we present a complete identification methodology based on squeezing tests.     

基于非局部通道注意力机制的单图像超分辨率方法

单图像超分辨率是一个不适定的问题,是指在给定模糊和低分辨率图像的情况下重建纹理图案。卷积神经网络（CNN）最近被引入超分辨率领域中,尽管当前研究通过设计CNN的结构和连接方式获得了出色的性能,但是忽略了可以使用边缘数据来训练更强大的模型,因此提出了一种基于边缘数据增强的方法,即单图像超分辨率的非局部通道注意力（NCA）方法。该方法可以充分利用训练数据并通过非局部通道注意力提高性能。所提方法不仅为设计网络提供了引导,而且也可以对超分辨率任务进行解释。非局部通道注意力网络（NCAN）模型由主分支和边缘增强分支组成,通过往模型里输入低分辨率图像并预测边缘数据,使主分支自注意力重建超分辨率图像。实验结果表明,在BSD100基准数据集上与二阶注意力网络（SAN）模型相比,NCAN在3倍放大因子下的峰值信噪比（PSNR）和结构相似度（SSIM）分别提升了0.21 dB和0.009;在Set5、Set14等其他基准数据集上与深度残差通道注意力网络（RCAN）模型相比,NCAN在3倍和4倍放大因子下的PSNR和SSIM都取得了较为明显的提升。NCAN在可比参数方面性能超过了最新模型。     

结合同伦代理模型的静力贝叶斯随机模型修正

为了使用随机静力位移测量数据对结构有限元模型进行修正,并保证计算效率,提出了一种同伦代理模型与贝叶斯抽样方法结合的随机模型修正方法。首先以结构静力位移构建目标函数,然后采用延缓拒绝自适应抽样算法对修正参数的后验概率密度进行估计。抽样过程中,采用同伦代理模型替代有限元模型对结构静力位移进行计算。数值算例和试验结果表明：进行变截面梁的有限元模型修正时,与二次响应面模型相比,在静力贝叶斯模型方法中利用同伦代理模型,修正参数的后验概率密度能更准确地复现结构随机响应,使修正后的结构随机响应与测量结果概率密度函数更加吻合。即使在随机测量误差的变异系数较大、先验信息与真实修正参数之间差异较大时,所提方法仍能够快速得到修正参数的后验概率密度,使修正参数计算的结构随机位移响应与测量结果的概率密度函数保持一致。同伦代理模型结合贝叶斯抽样算法能在概率框架内快速而准确地对结构进行随机模型修正。     

Analyse théorique et expérimentale des effets thermiques dans les butées hydrodynamiques à géométrie fixe

Theoretical and experimental analysis of thermal effects in fixed geometry thrust bearings. This paper deals with both theoretical and experimental analyses of thermal phenomena in thrust bearings. The test allowed us to measure the pressure and the temperature fields and the minimal film thickness separating the two surfaces in relative motion. The experimental data are obtained on a hydrodynamic thrust bearing with eight fixed pads. The influence of operating conditions (applied load and rotational speed) on the thrust bearing performance is also analysed. The numerical simulation is done using a thermohydrodynamic computer code taking into account the local thermal effects.     

新型硅丙乳液在水性无机富锌涂料中的应用

利用乙烯基三乙氧基硅烷对电气石粉表面进行包覆改性,再以原位聚合的方式将其引入至硅丙乳液的聚合过程中,合成了一种新型硅丙乳液,并以此作为有机成膜物质,添加至无机硅酸钾溶液中,制得富锌涂料。通过扫描电镜(SEM)和能谱(EDS)对包覆改性后的电气石粉及其涂膜进行表征;使用电化学阻抗谱(EIS)测试了富锌涂层的耐蚀性。结果表明:由引入了电气石粉合成的新型硅丙乳液制得的改性富锌涂层的附着力、柔韧性及耐蚀性明显提高,同时具有防闪锈功能。     

Reconfigurable address generator for multi-standard interleaver

This paper presents low-complex and novel techniques for designing reconfigurable architectures for multi-standard address generator and interleaver. The emphasis of this work is on hardware re-use, but it also focuses on optimizing the hardware to support multiple standards. A low-cost reconfigurable architecture for address generator and interleaver is proposed which operates in WLAN (802.11a/b/g and 802.11n), WiMAX (802.16e) and 3GPP LTE standards. A simple algorithm and a reconfigurable architecture that eliminates the computationally intricate mod function for LTE, and floor as well as mod function for WLAN/WiMAX, are proposed to reduce the hardware cost as well as implementation complexity. Novel architectures are also proposed to select the increment values for 16-QAM and 64-QAM schemes. A unique configurable subtracting sub-block for each modulation scheme is also presented. Software simulation is carried out to authenticate the functionality of the algorithm. The proposed reconfigurable architectures are realized on FPGA and tested on board. Synthesis results on Spartan-3 FPGA display 66% reduction in FPGA resource utilization and 74% increase in operating frequency compared to the cited address generators. Implementation results on Kintex UltraScale FPGA display a reduction of 34% in resource utilization and 20% in total on-chip power compared to the cited interleavers. This design is also implemented using 45 nm CMOS standard cell technology, and ASIC synthesis results of the reconfigurable address generator exhibit 76.4% improvement in data rate and 52.23% decrease in latency compared to the state-of-the-art address generators. The proposed multimode interleaver also exhibit 60.28% reduction in hardware complexity.     

基于同伦分析方法的随机结构静力响应求解

该文提出了一种基于同伦分析方法的求解含随机参数结构的静力响应的新方法。该方法将随机静力平衡方程重新进行同伦构造,利用含随机变量和趋近函数的同伦级数展式来表示结构的随机静力位移响应,该同伦级数的各阶确定性系数和趋近函数可通过对一系列的变形方程求解得到。由于趋近函数的引入,该同伦级数解相较于传统的摄动法有更大的收敛范围,对于含较大变异性随机参数的结构也能获得不错的求解精度。同时,该文提出了一种降维策略来提高该方法的计算效率。数值算例表明,与目前广泛应用的广义正交多项式展开法（GPC）相比,从计算精度上看,该文方法的3阶展开与GPC 2阶展开相当,该文方法的6阶展开与GPC 4阶展开相当,而计算时间上前者均明显少于后者。此外,该文方法也可以方便地应用到随机结构的几何非线性分析当中,并具有较好的计算精度和计算效率。