Fracture‐Based Fabrication of Normally Closed,Adjustable, and Fully Reversible Microscale Fluidic Channels

Adjustable fluidic structures play an important role in microfluidic systems. Fracture of multilayered materials under applied tension has been previously demonstrated as a convenient, simple, and inexpensive approach to fabricate nanoscale adjustable structures; here, it is demonstrated how to extend this concept to the microscale. This is achieved by a novel pairing of materials that leverages fracture mechanics to limit crack formation to a specified region, allowing to create size‐controllable and adjustable microfluidic structures. This technique can be used to fabricate “normally closed” microfluidic channels that are completely reversible, a feature that is challenging to achieve in conventional systems without careful engineering controls. The adjustable microfluidic channels are then applied to mechanically lyse single cells, and subsequently manipulate the released nuclear chromatin, creating new possibilities for epigenetic analysis of single cells. This simple, versatile, and robust technology provides an easily accessible pathway to construct adjustable microfluidic structures, which will be useful in developing complex assays and experiments even in resource‐limited settings.     

Electrochemical hydrogen storage behaviors of ultrafine Co-P particles prepared by direct ball-milling method

Ultrafine particles of Co-P were synthesized by direct ball milling of Co and P powders and also investigated as a reversible hydrogen storage electrode material. The electrochemical results demonstrated that the reversible charge-discharge capacity of the Co-P electrode can reach more than 300 mA h/g. In addition, the cycling ability and high rate capability of the Co-P electrode are excellent with only 5% capacity decay after 100 cycles at a high rate of 300 mA/g. The temperature-programmed desorption measurements (TPD) of the Co-P electrode revealed that the charge and discharge reactions of the Co-P electrode proceeds predominantly through electrochemical hydrogen storage mechanism and the electrooxidation of cobalt contributes only a negligible part to the reversible electrochemical capacity.     

Reversibility of Asphaltene Deposition Under Dynamic Flow Conditions

Occurrence of asphaltene deposition in production formation constitutes one of the most serious problems currently encountered in the petroleum industry in many areas of the world. Reversibility of asphaltene deposition causes crucial argument and controversy in laboratory research of the petroleum industry. A deeper understanding of this phenomenon is the key for treatment of the problem of asphaltene deposition. The major goals of this study were to investigate 1) asphaltene adsorption rate on carbonate rock surfaces under static condition, and 2) asphaltene deposition and its reversibility under dynamic flow conditions. For the sake of achieving these goals, two groups of experiments were undertaken. The first one measured asphaltene adsorption rate under static condition, while the second group was devoted to studying reversibility of asphaltene deposition under dynamic flow condition through actual porous medium. The results of the study indicated that the increase of aging time increases asphaltene adsorption on carbonate rock surfaces under static condition. However, the major part of asphaltene is adsorbed during the first 30 h of contact of oil with the rock surface. The results of dynamic flow experiments showed that asphaltene deposition is a continuous process causing permeability damage and is also partially reversible. Furthermore, the asphaltene deposition causes more damage in low permeability rock than one in higher permeability. The obtained results are expected to have important implications for better formulation of treatments of asphaltene deposition.     

An empirical analysis of lumpy investment: the case of US petroleum refining industry

This paper employs five econometric models to examine lumpy investment and investigates the investment behavior of the US petroleum refining industry. Firms in the industry are classified into three groups by their size. All three groups show zero investment, disinvestment and investment in accordance with economic conditions. The analysis finds the minimum amount of investment and disinvestment for each group, which suggests that the size of fixed costs of investment is substantial, regardless of firm size. However, small firms adjust capital stock more slowly than medium or large firms. The analysis also suggests the existence of a convex adjustment cost.     

高压真空换向接触器在提升机中的应用

矿用提升机原高压换向电路频繁出现故障,现以JGZH型真空高压换向接触器替代原空气式高压换向器进行技术改造,改造后提升机性能可靠,达到安全运行.     

Hydrogen adsorption on supported cobalt,iron, and nickel

This paper emphasizes concepts and fundamentals relating to the kinetics, energetics, and stoichiometries of adsorption of hydrogen on supported cobalt, iron and nickel, with emphasis on nickel. Relationships between catalyst and adsorption properties and the application of hydrogen chemisorption to the measurement of metal surface areas are discussed. Evidence is presented for nonstoichiometric adsorption of hydrogen on supported metals and the results are interpreted in terms (i) reversibility of adsorption and (ii) interactions of hydrogen with metal oxides present on or near metal crystallites. Contamination of the metal surface by support moieties can cause (i) the appearance of new adsorption states of hydrogen at higher binding energies and (ii) an increase in the adsorption activation energy for hydrogen which can lead to severe kinetic limitations in the adsorption process. Precalcination treatments and promoters such as potassium also cause the appearance of new high temperature adsorption states and significantly increase the adsorption activation energy for hydrogen.     

Property analysis of logic Petri nets by marking reachability graphs

Logic Petri nets (LPNs) are suitable to describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. To investigate the dynamic properties of LPNs directly, a new method for analyzing LPNs is proposed based on marking reachability graphs in this paper. Enabled conditions of transitions are obtained and a marking reachability graph is constructed. All reachable markings can be obtained based on the graph; the fairness and reversibility of LPNs are analyzed. Moreover, the computing complexity of the enabled conditions and reachable markings can be reduced by this method. The advantages of the proposed method are illustrated by examples and analysis.