声波层析成像技术

随着我国经济的发展，各类基础设施大量兴建，对岩体的工程性质研究，混凝土构件的质量和强度检测，提出了更高的要求，因此，需要提出新的研究方法和手段，以满足工程的需要，声波层析成像技术在岩石力学研究、混凝土质量检测中有广阔的应用前景。对该技术的原理，方法作了详细介绍，并通过模型试验和应用实例，说明了该技术的特点和效果。     

Nanoporous aluminum oxide membranes for filtration and biofunctionalization

Nanoporous aluminum oxide membranes with high open porosity are prepared by anodic oxidation. Conventional self-supporting as well as mechanically stabilized nanoporous membranes are produced from aluminum plates and microimprinted aluminum foils, respectively. The mechanically stabilized membranes are characterized by very thin membrane parts stabilized by surrounding thick bridges. The minimal thickness of these thin membranes with open pores on both sides is 1 microm, with a mean pore size of the parallel open pores of 185 nm. With these two kinds of membrane the flow rates for cross filtration can be tuned over a wide range. With the mechanically stabilized membranes, substantially higher flow rates are achieved and experiments that cannot be performed with thicker membranes become possible. The biofunctionalization of the pore walls with archaebacterial tetraether lipids is realized and proved using aminated semiconductor nanocrystals. The lipid layer deposited on the pore walls also changes the filtration properties.     

基于重复控制的跟踪系统设计及应用

本文提出了一种电液伺服振动台系统跟踪控制的新方法。根据重复控制理论设计重复控制器,使系统的输出跟踪输入的周期性或重复性参考信号,从而达到跟踪控制的目的。重复控制器由重复补偿器和稳定化补偿器组成,文中对控制器的设计进行了详细的讨论,给出了设计实例和仿真结果。研究表明,应用这种方法设计的电液伺服振动系统可以实现对周期或重复性的振动实验信号的跟踪控制。     

Rheological properties of aqueous α A12O3 suspensions: Influence of dispersant concentration

The effects of concentration of polyacrylic acid as a dispersant on rheological properties of aqueous alumina suspensions have been investigated under steady and oscillatory shear conditions. At solid volume fractions between 0.45 and 0.6, a high degree of particle stabilization is achieved when 0.2 wt% of polyacrylic acid is added. At lower dispersant concentrations, suspensions exhibit pronounced irreversible thixotropic behaviour, whereas at higher dispersant concentrations, time dependent effects on the flow properties are not detectable. When the saturation adsorption limit of the polyelectrolyte on Al₂O₃ is reached, further addition of the dispersant appreciably changes the flow behaviour, as well as the viscoelastic response of investigated suspensions. The data under steady shear are described by application of the generalized Casson model, and for the analysis of viscoelastic data the generalized Maxwell model is used.     

On the physics of power,energy and economics of renewable electric energy sources - Part II

Renewable Energy Technologies (RETs) are often recognized as less competitive than traditional electric energy conversion systems. Obstacles with renewable electric energy conversion systems are often referred to the intermittency of the energy sources [1] and the relatively high maintenance cost. However, due to an intensified discourse on climate change and its effects, it has from a societal point of view, become more desirable to adopt and install CO₂ neutral power plants. Even if this has increased the competitiveness of RETs in a political sense, the new goals for RET installations must also be met with economical viability. We propose that the direction of technical development, as well as the chosen technology in new installations, should not primarily be determined by policies, but by the basic physical properties of the energy source and the associated potential for inexpensive energy production. This potential is the basic entity that drives the payback of the investment of a specific RET power plant. With regard to this, we argue that the total electric energy conversion system must be considered if effective power production is to be achieved, with focus on the possible number of full loading hours and the Degree of Utilization [2]. This will increase the cost efficiency and economical competitiveness of RET investments, and could enhance faster diffusion of new innovations and installations without over-optimistic subsidies. This paper elaborates on the overall problem of the economy of renewable electric energy conversion systems by studying the interface between physics, engineering and economy reported for RET power plants in different scientific publications. The core objective is to show the practical use of the Degree of Utilization and how the concept is crucial for the design and economical optimization disregarding subsidies. The results clearly indicate that the future political regulative frameworks should consider the choice of renewable energy source since this strongly affects the economical output from the RET power plants.     

Photoinitiator-free photopolymerization of acrylate-bismaleimide mixtures and their application for inkjet printing

There is growing interest in using photoinitiator-free systems in coating applications such as inkjet-printing, because residual photoinitiator can alter the properties of the resulting polymer. Bismaleimides (BMI) offer the opportunity to polymerize acrylates without the addition of photoinitiators, as this class of molecules can serve both as polymerizable monomer and as photoinitiator together with electron donor systems, like vinyl ether monomers or acrylates. The UV-induced copolymerization of a low-molecular-weight BMI with various acrylate monomers and oligomers without any photoinitiator was characterized. The BMI-acrylate systems show comparable polymerization speeds to widely used acrylic systems with photoinitiator. Superior thermal stability as well as thermomechanical properties are achieved by enhancing acrylics with BMI. Such photoinitiator-free systems lend themselves to be used for low-migration coatings as well as for high-temperature applications. Here, a characterization of selected BMI-acrylate mixtures regarding their photocuring kinetics and their application as inks for inkjet printing is shown. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47789.     

Spectroscopic and in vitro Investigations of Fe2+/α-Ketoglutarate-Dependent Enzymes Involved in Nucleic Acid Repair and Modification

The activation of molecular oxygen for the highly selective functionalization and repair of DNA and RNA nucleobases is achieved by α-ketoglutarate (α-KG)/iron-dependent dioxygenases. Of special interest are the human homologues AlkBH of Escherichia coli EcAlkB and ten-eleven translocation (TET) enzymes. These enzymes are involved in demethylation or dealkylation of DNA and RNA, although additional physiological functions are continuously being found. Given their importance, studying enzyme-substrate interactions, turnover and kinetic parameters is pivotal for the understanding of the mode of action of these enzymes. Diverse analytical methods, including X-ray crystallography, UV/Vis absorption, electron paramagnetic resonance (EPR), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy have been employed to study the changes in the active site and the overall enzyme structure upon substrate, cofactor, and inhibitor addition. Several methods are now available to assess the activity of these enzymes. By discussing limitations and possibilities of these techniques for EcAlkB, AlkBH and TET we aim to give a comprehensive synopsis from a bioinorganic point-of-view, addressing researchers from different disciplines working in the highly interdisciplinary and rapidly evolving field of epigenetic processes and DNA/RNA repair and modification.