Ablation behavior and thermal protection performance of TaSi2 coating for SiC coated carbon/carbon composites

For extending application of TaSi₂ in complex coating system, the ablation behavior and thermal protection performance of TaSi₂ coating is studied to evaluate its potential applications for anti-ablation protection of C/C composites. TaSi₂ coating is prepared by supersonic atmospheric plasma spraying (SAPS) on the surface of SiC coated carbon/carbon (C/C) composites. Phase variation and microstructure are characterized by XRD and SEM, respectively. During the ablation process, the coating is quickly oxidized to SiO₂ and Ta₂O₅ accompanied by a lot of heat consumption. The linear and mass ablation rates are 0.9?µm?s^?1 and ??0.4?mg?s^?1 after ablation for 80?s, respectively Results show that the prepared coating possesses optimal ablation performance under the heat flux of 2.4?MW/m². Moreover, the TaSi₂ coating and SiC inner coating have good chemical and physical compatibility during the ablation process. Therefore, the excellent performance of TaSi₂ coating during the ablation process makes it a candidate for anti-ablation protection for C/C composites.     

能源类国有企业投资项目后评价指标体系与程序设计

在系统地概括了能源类国有企业投资项目一般特点的基础上,分析了该类企业开展投资项目后评价的必要性和意义,提出了后评价的主要内容、指标体系设计、指标选取方法和基本工作程序,并对后评价工作的有效开展提出了相关建议。     

三苯基膦稳定金纳米粒子的合成及其特性研究

在水/乙醇混和体系中制备了三苯基膦稳定的金纳米粒子(GNPs)溶液。GNPs的粒径为5 nm,在548 nm有典型的表面等离子吸收。在不使用其它相转移分子的情况下,GNPs可以容易地转移到有机溶剂如二氯甲烷中,并得到可再分散于有机溶剂或水中的固体粉末,为制备可应用于不同的物理化学环境中的表面功能化GNPs提供了优异的初始化合物。     

Experimental investigation and analytical modelling of the effects of process parameters on material removal rate for bonnet polishing of cobalt chrome alloy

Cobalt chrome alloys are the most extensively used material in the field of total hip and total knee implants, both of which need highly accurate form and low surface roughness for longevity in vivo. In order to achieve the desired form, it is extremely important to understand how process parameters of the final finishing process affect the material removal rate. This paper reports a modified Preston equation model combining process parameters to allow prediction of the material removal rate during bonnet polishing of a medical grade cobalt chrome alloy. The model created is based on experiments which were carried out on a bonnet polishing machine to investigate the effects of process parameters, including precess angle, head speed, tool offset and tool pressure, on material removal rate. The characteristic of material removal is termed influence function and assessed in terms of width, maximal depth and material removal rate. Experimental results show that the width of the influence function increases significantly with the increase of the precess angle and the tool offset; the depth of the influence function increases with the increase of the head speed, increases first and then decrease with the increase of the tool offset; the material removal rate increases with the increase of the precess angle non-linearly, with the increase of the head speed linearly, and increases first then decreases with the increase of the tool offset because of the bonnet distortion; the tool pressure has a slight effect on the influence function. The proposed model has been verified experimentally by using different Preston coefficients from literature. The close values of the experimental data and predicted data indicate that the model is viable when applied to the prediction of the material removal rate in bonnet polishing.     

Thermal Conduction and Insulation Modification in Asphalt-Based Composites

The relationship between thermal conductivity and properties of mixing particles is required for quantitative study of heat transfer processes in asphalt-based materials. In this paper, we measured the e?ective ther- mal conductivity of asphalt-based materials with thermal conduction (graphite) and insulation (cenosphere) powders modification. By taking account of the particle shape, volume fraction, the thermal conductivity of filling particles and base asphalt, we present a new differential effective medium formula to predict the thermal conductivity modification in asphalt-based composite. Our theoretical predications are in good agreement with the experiment data. The new model can be applied for predicting the thermal properties of asphalt-based mixture, which is available for most of thermal modification in two-phase composites.     

基于KPLS的GM-AGC厚度预测方法

由于热连轧仅在精轧出口装有测厚仪,对带钢进行厚度控制时会产生严重的滞后,因此,GM-AGC常采用弹跳方程间接测厚的方法,但由于弹跳系数不易获得,且弹跳模型存在一定误差,这种方法不能有效提高带钢厚度质量.采用KPLS方法进行非线性特征抽取,获取辊缝、轧制力和厚度之间的相互关系,用于对带钢厚度进行预测,从而为GM-AGC提供较为精确的厚度预测值.     

超微粒氧化锌薄膜的制备及表面STM观测

作者在大气、常温环境条件下，对采用直流气体放电活化反应蒸发沉积法制备的超微粒氧化锌薄膜的表面构象进行了扫描隧道显微镜观察，获得了一些用传统电子显微镜所难以观察到的新现象，并结合工艺条件对其构象作了一定程序的解释，提出了热处理对其表面构象的影响。     

交变注采下储气库近井区断层失效风险敏感性量化评价

为综合量化评价交变注采下储气库近井区断层激活滑移失效风险,文中采用多个维度的断层滑移敏感性分析变量,构建注采前后不确定地应力耦合动态流压交变下的井壁断面剪切滑移失效风险量化指标.结果表明:1)多维度的参数分析能更全面地评估储气库近井区断面失效滑移敏感性;2)开度角是最能合理描述断层受流压扰动扩张及动态变化的敏感性指标;...     

基于DMADOV的12Cr1MoV异质接头焊接缺陷分析

通过对12Cr1MoV异质接头进行分析,运用DMADOV流程来提高焊接质量,对焊接过程中产生缺陷的原因进行分析,确定了焊接工艺优化方案,并对其进行验证。对焊接过程的主要缺陷类型进行定性、定量分析,运用有限元法对焊接过程进行焊接模拟,对相关的工艺参数进行优化改进。结果表明,焊接缺陷的成因是多方面的,焊接缺陷最主要的影响因素是焊接工艺参数的设置,通过对焊接工艺参数设置的优化可以提高焊接质量,其中焊接过程中是否进行焊前焊后热处理以及焊接过程中的管理水平也非常重要。     

异步电动机无速度传感器控制策略的研究现状与进展

速度辨识是无速度传感器控制的关键技术。在异步电动机无速度传感器控制系统中速度辨识的方法有许多种,例如模型参考自适应方法（MRAS）,观测器法,卡尔曼滤波器法,神经网络法等。这些方法利用估计得到的转速值能对异步电动机进行很好的调速控制,但无速度传感器控制的关键在于磁链的准确观测,由于电机参数随环境的变化以及参数调节的实时性,使得精确观测磁链的难度加大,因而这些方法在实际的工业应用中大受限制。本文着重分析一些基本方法,并给出它们的优缺点及估计转速的可行性。