一种基于改进的HHT短期风电功率预测方法

风电功率短期预测对于电力系统稳定性和电能质量的提高具有非常重要的意义。文章采取一种基于Hilbert-Huang变换风电的短期预测方法。首先,对经验模态分解(EMD)中原始数据存在的端点效应利用提出的延拓抑制方法进行了抑制,然后,用经验模态分解的方法将风电场历史功率数据分解得到了七个具有不同规律特征的分量,进行希尔伯特变换,并在对各个成分的特点分析的基础上分别搭建了不同的预测模型,然后结合多个预测模型对风电场历史功率数据进行组合预测。仿真实验预测结果表明该方法使得风电预测精度大大提高,具有很好的应用前景。     

活门组件综合试验器研制

活门组件综合试验器是专门为检测飞机活门组件和独立活门的性能指标而开发的一种新型试验设备。针对试验器的基本技术要求,给出了该试验器液压控制系统原理图、电气控制系统硬件组成框图及软件系统的工作流程图,并着重就开发中所遇到的重点、难点进行了较详细的介绍,同时验证了设计方案的正确性。     

偏心缩套液压缸界面压力模型及有限元分析

为了研究偏心缩套缸体的界面应力分布规律,建立了偏心缩套缸体的数学模型,通过工程实例计算与有限元结果对比,结果表明缸体界面压力模型理论值与有限元计算值相吻合。此外,由此数学模型可知偏心缩套缸体界面压力均沿圆周分布不均,且呈减小趋势。     

Enhanced performance of solid oxide fuel cell fabricated by a replica technique combined with infiltrating process

For the convenience of hermetic sealing, first time, a replica technique is successfully invented in this study to fabricate the dissymmetrical tri-layer structure of “porous La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) |dense LSGM| porous LSGM” skeleton by adopting a carbon layer. SEM analysis reveals that the bonding strength of interfacial contact between dense LSGM and porous LSGM can also be improved when using this new fabrication method. Metal Ni and layered perovskite oxide SmBa_0.5Sr_0.5Co₂O₅ (SBSCO) are then infiltrated into the dissymmetrical skeleton on each side to form the functional fuel cell. The OCV are close to the expected Nernst potentials which demonstrate that the cell fabricated in this study can be well sealed. The maximum power densities of functional fuel cell with configuration of “Ni–LSGM |LSGM| LSGM–SBSCO” are 0.12 W cm⁻², 0.38 W cm⁻², 1 W cm⁻² and 1.8 W cm⁻² at 400, 450, 500, 550 °C, respectively. Though long term stability testing shows a rapid performance degradation when discharged at 0.7 V for 80 h, by changing pure Ni to Ni–SDC mixed oxide, the performance of functional fuel cell with configuration of “Ni–SDC–LSGM |LSGM| LSGM–SBSCO” increases and the long term stability is largely improved.     

Synthesis of poly(acrylate-styrene)/poly(acrylate-styrene) core/shell latex and TOPEM-DSC characterization

Poly(acrylate-styrene)/poly(acrylate-styrene) core/shell latex particles were synthesized via seeded semi-continuous emulsion polymerization. Both core polymer (CP) and shell polymer (SP) were copolymerized by using three identical monomers of methyl methacrylate (MMA), butyl acrylate (BA) and styrene (St) with different composition ratios. The synthesized core/shell latex particle presents a phase separated state with the interfacial layer between CP and SP. In this study, the weight fractions and the corresponding thickness of this interfacial layer, CP and SP phase in the core/shell latex particle has be successfully calculated by using multi-frequency temperature-modulated differential scanning calorimetry (TOPEM-DSC). The results indicate that the interfacial layer thickness of the core/shell latex particle is determined by the core/shell structure, such as hard core/soft shell (defined as HC/SS) and soft core/hard shell (defined as SC/HS), the glass transition temperature (T_g) of the “hard” phase (correspondingly core or shell for HC/SS or SC/HS structure, respectively), and the existence of hydrophilic monomer during the copolymerization process such as acrylic acid. Meanwhile, the influence of film-formation-temperature on the microstructure of the latex films was systematically explored in this work.     

Thermomechanical and Interfacial Properties of Calcium Alginate Fiber-Reinforced Polypropylene Composites

Polypropylene (PP) matrix calcium alginate fiber reinforced unidirectional composites (10% fiber by weight) were fabricated by compression molding. Tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM), and impact strength (IS) were found to be 26 MPa, 950 MPa, 38 MPa, 1320 MPa, and 20 kJ/m², respectively. Degradation tests of composites were performed for 6 weeks in soil and it was found that composites retained almost 75% of its original strength. The interfacial properties of the composite were investigated by using single fiber fragmentation test (SFFT) and by scanning electron microscope (SEM).     

MODELING LIQUID MASS TRANSFER IN HIGEE SEPARATION PROCESS

Correspondence concerning this paper should be addressed to Professor Richard S.H. Mah. Hsien-Hsin Tung is now affiliated with Department of Chemical Engineering, California Institute of Technology

Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process.     

Some Fundamental Issues in Adhesion: A Conceptual View

The role of interfacial interactions in determining the global response of joint systems is discussed in relation to the question of true interfacial failure and the ubiquitous occurrence of interphases. The discussion is from the point of view of systems involving adhesives, coatings and composites rather than, e.g., particle-particle or particlesubstrate systems and is strictly conceptual in nature. It is proposed that interfacial interactions, rather than directly exerting an effect on the global response of joint systems, are instead the driving force for the many and varied processes that create interphases. It is such interphases, or transition zones between phases, which affect the global mechanical response of joint systems.     

MODELING THE PEEL PERFORMANCE OF PRESSURE-SENSITIVE ADHESIVES

This article presents an approach to analyzing the peel behavior of pressure-sensitive adhesives (PSAs) using the finite element method. The rheological properties and the peel strength of four natural-rubber–based PSAs were experimentally measured to provide input for and comparison with the finite element modeling. A criterion based on stored elastic energy density was used to describe the interfacial debonding. It was shown that the finite element predictions essentially captured the general features of the peel behavior of the PSAs. However, the peel forces predicted were lower than the experimental measurements at intermediate and high peel rates. This might be related to the fact that the nonlinear viscoelastic behavior of the PSAs at large deformation was not considered in this study.     

Peeling of PSAs on Viscoelastic Substrates: A Failure Criterion

This work deals with the study of the viscoelastic and adherence properties of pressure-sensitive adhesive (PSA) formulations dedicated to medical applications. We have developed a specific viscoelastic substrate to measure the adherence properties of PSAs that mimics adhesion on human skin. In the present article, we describe several experiments dedicated to a better understanding of adhesion on viscoelastic substrates without discussing specifically the case of human skin. In this way, we have studied different model adhesive formulations based on real medical formulations, and we have related the rheological behavior to the adherence properties obtained on different substrates to study the various specific effects due to the viscoelasticity of soft substrates. We propose from this study a failure criterion that allows one to derive a reasonable estimate of the peeling transition rate from cohesive to interfacial or stick–slip failure.