Research on resistance characteristics of secondary air damper and nozzle in pulverized coal boiler

This article provides an industrial application method for monitoring and regulating the secondary air through the burner nozzle of a tangentially fired boiler. A geometric model from the inlet of the damper to the burner nozzle was established, which divides the grid for numerical calculation of the flow field to get the drag coefficients of the nozzle and damper under different opening ratios of the damper. In the range of 20–70% opening, the damper has perfect regulation performance, which has the main resistance comparing with that of nozzle. The disc-type damper has a slightly larger resistance than that of the splayed one. A precise corresponding function relationship between the opening ratio and the gas flow rate was established, and base on which, an exact control method on the secondary air damper was proposed. The result can apply to the intelligent transformation of thermal power plants to save energy and reduce consumption.     

石油储罐防腐涂料施工策略

在经济不断发展的背景下,石油已经成为不可或缺的能源,其从开采至加工整个过程均需使用储油罐,所以储油罐的防腐质量十分重要,需要使用相应的涂料进行防腐。本文对石油储罐防腐涂料施工策略进行分析,以供参考。     

Histidine as a key modulator of molecular self-assembly: Peptide-based supramolecular materials inspired by biological systems

Histidine, a versatile proteinogenic amino acid, plays a broad range of roles in all living organisms and behaves as a key mediator of the interactions of biomolecules with inorganic constituents. The self-assembly of histidine-rich peptides and proteins is critical in biology, as the histidine unit is both a multifunctional regulator and an ideal motif for the construction of complex biological structures. In particular, non-covalent interactions between the imidazole ring and other molecular building blocks and metal ions are routinely employed to generate these complexes. Therefore, this strategy can be duplicated in an artificial context to create sophisticated bioactive materials. In this review, we first highlight a clear perspective of the bio-inspired design strategies which can replicate the hierarchical structure of biological systems allowing the engineering of the supramolecular self-assembly of histidine-functionalized peptides. We further summarize advancements in the field of peptide supramolecular structures incorporating histidine residues in the peptide backbone to generate organized functional supramolecular biomaterials with customizable features. We also discuss significant advances and future prospects in supramolecular self-assembly of histidine-functionalized peptides, as well as provide an overview of advanced techniques for the fabrication of histidine-based biomaterials for bio-nanotechnology, optoelectronic engineering, and biomedicine. Overall, artificial supramolecular materials based on histidine functionalized peptides, motivated by the intriguing properties discovered in natural proteins, bear the potential to boost the creation of sustainable bio-inspired materials.     

基于NB分类器重访概率预测的Web缓存替换策略

Web缓存是用来解决网络访问延迟和网络拥塞问题，缓存替换策略直接影响缓存的命中率。为此，提出一种朴素贝叶斯（NB）分类器重访概率预测的Web缓存替换策略；根据用户之前访问日志，通过分区操作提取多项特征来表示每次访问的对象，并构建特征数据集；训练NB分类器，用来确定缓存中对象被再次访问的概率，为对象分配权重；结合LRU策略来合理删除一些对象。仿真结果表明，提出的策略在保证较高命中率的同时有效降低了执行时间。     

Corporate performance of the Seven Brothers of the European energy market: Then there were five

Fifteen years ago, Thomas (2003) found that seven European energy utilities had a strong hold over European energy markets. By 2009, further concentration had occurred, with five large utilities becoming more dominant. However, by 2015, while the market share of these five companies remained intact, their strength was waning. Sales and profits were declining, and their credit ratings suffering. Contributing factors were poor corporate strategy, competition from new entrants, and a shift from large, complex technologies to smaller, decentralised options. The challenge for the Big Five is to embrace new business models and transform themselves into more nimble companies.     

多维不确定性影响下的水期权交易最优策略研究

为解决来水预测不确定性和水价不确定性给用水户带来的风险对冲问题,引入对冲性的水期权交易模式,建立了以用水户期望收益最大为目标的水期权交易模型,得到了最优的期权交易策略应满足的条件,并利用二分法计算得到了最优的期权交易策略,探究了来水不确定性与水价不确定性对期权交易策略的影响。结果表明,来水预测误差和水价的波动越大,用水户的期望收益越大,最优的期权交易策略能有效降低来水预测不确定性和水价不确定性带来的风险。     

高碾压混凝土重力坝分区材料-结构界面特性与变形协调仿真分析

高碾压混凝土重力坝不同功能部位"结构特性"与"材料性能"的差异产生的变形协调问题直接关系到工程结构的安全运行,现阶段变形协调分析多是对结构变形和受力进行分析,对异种材料变形协调机理认识不足,缺乏理论基础研究。本文基于界面力学理论,考虑混凝土坝分区中常见的两种双材料界面形式与理想界面的连续边界条件,基于奇异性特征值的特征方程,提出了以应力奇异性特征值作为异种材料变形协调的评价指标,并通过有限元分析验证了理论计算的正确性与有效性;进而分析了界面结合角度和异种材料组合对单侧自由界面端与埋入界面折点处应力奇异性的影响,通过非均质有限元数值仿真分析了复合试件破坏模式,研究了抗压强度与应力奇异性特征值的关系;最后通过统计实际混凝土坝工程中不同坝段内的双材料界面的材料参数(弹性模量)与结构参数(界面形式与结合角度),计算奇异性特征值,评价了该工程中界面的变形协调特性,为高混凝土坝分区材料-结构设计与材料选取提供新的思路。     

Nonlinear optimization strategy based on multivariate prediction capability ratios: Analytical schemes and model validation for duplex stainless steel end milling

Given the complex nature of their phenomena and interactions, industrial processes often have multiple variables of interest, usually grouped into critical-to-quality and critical-to-performance characteristics. These variables often have significant correlations, which make engineering problems multivariate. For this reason, Response Surface Methodology, coupled with multivariate techniques, has been widely used as a logical roadmap for modeling and optimization of the characteristics of interest. However, the variability and prediction capability of the numerical solutions obtained are almost always neglected, reducing the likelihood that numerical results are indeed compatible with observable process improvements. To fill this gap, this paper proposes a nonlinear multiobjective optimization strategy based on multivariate prediction capability ratios. For this, rotated Factor Analysis is used as the multivariate technique for grouping process characteristics and composing capability ratios, so that the prediction variance is taken as the natural variability of the process modeled and the expected value distances to the nadir solutions of the latent variables are taken as the allowed variability. Normal Boundary Intersection method, combined with Generalized Reduced Gradient algorithm, is used as the numerical scheme to maximize the prediction capability of Pareto optimal solutions. To illustrate the feasibility of the proposed strategy, we present a case study of end milling without cutting fluids of duplex stainless steel UNS S32205. Rotatable Central Composite Design, with three cutting parameters, was employed for data collection. Traditional multivariate and proposed approaches were compared. The results demonstrate that the proposed optimization strategy is able to provide solutions with satisfactory prediction capability for all variables analyzed, regardless of their convexities, optimization directions, and correlation structure. In addition, while critical-to-quality characteristics are more difficult to control, they have been favored by the proposed optimization regarding prediction capability, which was a desirable result.     

车辆高速避让路径跟踪控制策略

建立车辆动力学模型,研究车辆在高速避让工况下的路径跟踪控制策略。基于自抗扰控制设计车辆横摆角速度以及道路曲率2种不同的路径跟踪控制器;设计基于车辆偏航位移和偏航角度加权的线性二次最优控制器;对3种控制器控制效果进行仿真验证,分析路径跟踪侧向位移误差、侧向加速度、前轮转向角以及偏航角度变化。越野车实车测试结果表明,路径跟踪控制策略正确。