Bond graph modeling,design and experimental validation of a photovoltaic/fuel cell/ electrolyzer/battery hybrid power system

This work presents a complete bond graph modeling of a hybrid photovoltaic-fuel cell-electrolyzer-battery system. These are multi-physics models that will take into account the influence of temperature on the electrochemical parameters. A bond graph modeling of the electrical dynamics of each source will be introduced. The bond graph models were developed to highlight the multi-physics aspect describing the interaction between hydraulic, thermal, electrochemical, thermodynamic, and electrical fields. This will involve using the most generic modeling approach possible for managing the energy flows of the system while taking into account the viability of the system. Another point treated in this work is to propose. In this work, a new strategy for the power flow management of the studied system has been proposed. This strategy aims to improve the overall efficiency of the studied system by optimizing the decisions made when starting and stopping the fuel cell and the electrolyzer. It was verified that the simulation results of the proposed system, when compared to simulation results presented in the literature, that the hydrogen demand is increased by an average of 8%. The developed management algorithm allows reducing the fuel cell degradation by 87% and the electrolyzer degradation by 65%. As for the operating time of the electrolyzer, an increment of 65% was achieved, thus improving the quality of the produced hydrogen. The Fuel Cell's running time has been decreased by 59%. With the ambition to validate the models proposed and the associated commands, the development of this study gave rise to the creation of an experimental platform. Using this high-performance experimental platform, experimental tests were carried out and the results obtained are compared with those obtained by simulation under the same metrological conditions.     

Beneficial effects of wettability altering surfactants in oil-wet fractured reservoirs

In fractured reservoirs, an effective matrix-fracture mass transfer is required for oil recovery. Surfactants have long been considered for oil recovery enhancement, mainly in terms of their ability to reduce oil–water interfacial tension. These surfactants are effective when the fractured formations are water-wet, where capillary imbibition of surfactants from the fracture into the matrix contributes to oil recovery. However, another beneficial aspect of surfactants, namely their ability to alter wettability, remains to be explored and exploited. Surfactants capable of altering wettability can be especially beneficial in oil-wet fractured formations, where the surfactant in the fracture diffuses into the matrix and alters the wettability, enabling imbibition of even more surfactant into the matrix. This sequential process of initial diffusion followed by imbibition continues well into the matrix yielding significant enhancements in oil recovery.In order to test this hypothesis of sequential diffusion–imbibition phenomenon, Dual-Drop Dual-Crystal (DDDC) contact angle experiments have been conducted using fractured Yates dolomite reservoir fluids, two types of surfactants (nonionic and anionic) and dolomite rock substrates. A new experimental procedure was developed in which crude oil equilibrated with reservoir brine has been exposed to surfactant to simulate the matrix-fracture interactions in fractured reservoirs. This procedure enables the measurements of dynamic contact angles and oil–water interfacial tensions, in addition to providing the visual observations of the dynamic behavior of crude oil trapped in the rock matrix as it encounters the diffusing surfactant from the fractures. Both the measurements and visual observations indicate wettability alterations of the matrix surface from oil-wet to less oil-wet or intermediate wet by the surfactants. Thus this study is of practical importance to oil-wet fractured formations where surfactant-induced wettability alterations can result in significant oil recovery enhancements. In addition, this study has also identified the need to include contact angle term in the dimensionless Bond number formulations for better quantitative interpretation of rock–fluids interactions.     

Nondestructive characterization of the mechanical strength of diffusion bonds. II. Application of a quasi-static spring model

It has been shown that the acoustic response of imperfect interfaces may be described by a quasi-static spring model. In the present paper, experimental data on the geometry of the contacts between two diffusion-bonded blocks have been used to determine the spring stiffness of such interfaces which have been correlated with experimentally determined ultrasonic reflection coefficients. The correlation between the theoretical reflection coefficient and the spring stiffness was found to be in excellent agreement with experimentally-observed values, if the disbonds are of infinitesimally small thickness. For disbonds of finite thickness, the agreement is less satisfactory. Reasons for the discrepancy in the latter case are unknown at the present time.     

Pullout behavior of polypropylene fibers from cementitious matrix

A comprehensive experimental investigation was performed to understand the pullout behavior of polypropylene fibers from a cementitious matrix. The effect of embedded length on the pullout characteristics, the development of the interfacial bond with age of curing of matrix and the effect of exposure to degrading environments, like seawater and salt water, on the interfacial bond between the fibers and cementitious matrix were studied. The aim of these experiments was to understand the properties of fiber/matrix interface, which are of primary significance in predicting the overall behavior of fiber-reinforced cement-based composites. Polypropylene fibers have a weak bond with cementitious matrix because of smooth surface of fibers, which does not allow for sufficient friction to develop between the two. In this study a new method to improve the frictional bond by means of mechanical indentations of fibers was also proposed. The bonding performance was characterized by means of pullout tests of the plain and modified fibers from a cementitious matrix. An optimum level of fiber modification for maximization of bond efficiency was determined experimentally.     

NA—5聚氨酯胶粘剂对金属粘接强度的影响

以ＮＡ－５型氨酯胶粘剂作为金属五ＰＵ弹性胶料之间的胶粘剂，制作钢／ＰＵ橡胶／铝静件。研究了影响制件粘接强度的主要因素，给出了ＮＡ－５最佳粘接工艺。     

Influence of fly ash and its mean particle size on certain engineering properties of cement composite mortars

An experimental investigation on the effects of incorporating large volumes of fly ash on the early engineering properties and long-term strength of masonry mortars is reported. The effect of fly ash and its mean particle size (PD) on the variation of workability and strength has been studied. It was found that fly ash and its mean particle size play a very significant role on the strength of masonry mortars. It has been observed that the early-term strength, except the mortars incorporating coarse fly ash (CFA), was slightly influenced by the replacement with fly ash. The long-term strength (both the bond strength and the compressive strength) will significantly increase, especially for the bond strength of mortars incorporating coarse fly ash. It was also found that the bond strength significantly increased as the mean particle size of fly ash decreases after 28 days curing. However, the 7-day strength was little influenced by fly ash particle size. The fluidity of composite mortar enhanced due to replace cement and lime with fly ash, and the mean PD of fly ash significantly influenced the workability.     

Modeling bond strength of corroded reinforcement without stirrups

Deterioration of bond strength between concrete and reinforcement is of great importance in studying the strength of structural members with corroded reinforcements. A simple analytical model is proposed to demonstrate the effect of corrosion of reinforcing bar on reduction of bond strength. The corrosion pressure due to expansive action of corrosion products before and after corrosion cracking is firstly estimated. Then, reduction of bar confinement caused by cover cracking, change of friction coefficient between the steel and the concrete, and reduction of the friction force on the bearing face as well as deterioration of the ribs of the deformed bars due to steel corrosion are considered in calculating the mechanical interactions between reinforcing bar and concrete. As a result, the bond strength of corroded bars is calculated. The theoretical results are compared with the experimental results and agree with those results well.     

基于BondGraph模型的定性故障诊断方法

研究一种基于键合图（Bond Graph）模型的定性故障诊断方法。根据Bond Graph模型元件中有关参数和变量的特定因果关系,推导出当某观测参量发生变化时,系统内所有可能产生故障的部位,并在此基础上预测每个故障的将来状态,通过与系统实际观测特征比较,在可能产生故障的集合中准确定位故障源。通过实例仿真验证,该方法是便捷有效的。     

并列短语及其词序的认知语言学研究

有关并列短语及其词序的研究目前主要存在四方面的问题：“并列短语”的概念之争、并列短语的界定、并列短语与并列复合词的异同、并列短语的词序。为解决这些问题与分歧,认知语言学的基本观点、假设、范畴的原型观、语言的象似观、概念整合理论以及词汇化和短语固化等理论和观点构成研究并列短语及其词序的理论基础,该理论能在一定程度上对以上问题作出合理的解释。根据范畴的原型观,并列短语具有典型性,为并列短语及其词序研究尤其是定量研究提供了理论基础;象似性在并列短语中大量存在,尤其是顺序象似或时间顺序原则,在汉语中尤为明显;词语整合具有层级性,并列短语在词汇化和固化程度上的不同,与概念的整合层级性相关。     

陶瓷结合剂CBN砂轮磨削表面粗糙度的试验研究

本文通过一系列的试验，研究了陶瓷结合剂CBN砂轮磨削表面粗糙度的变化规律及其特点，建立了相应磨削表面粗糙度的经验公式。