Tunable multifunction logic modules based on parametric representation of functions of k-valued logic over quasifields

We propose a new class of tunable logic modules that realize functions of k-valued logic. These modules are characterized by homogeneous structure and linear dependence of the number of tunable inputs on the number of input variables.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 24–29, July–August, 1991.     

Hydration kinetics of high-performance cementitious systems under different curing conditions

Curing plays an essential role in the modern concrete technology, since it has a crucial effect on the development of concrete properties. High-performance cementitious systems are especially sensitive to the applied curing methods because of self-desiccation and high sensitivity to early-age cracking. Thus, it is of particular interest to compare the efficiency of internal curing and traditional curing techniques such as sealing and water ponding. In this study, the efficiency of different types of curing was estimated by means of isothermal calorimetry. Four different water to cement (w/c) ratios in the range of 0.21–0.45 and four types of curing were studied, including sealing, water ponding with different amount of water, internal curing by saturated lightweight aggregate and super-absorbent polymer. The hydration degree was determined using heat of hydration data. Compressive strength of the tested specimens was measured and analyzed. The results indicate that efficiency of different types of curing strongly depends on w/c ratio.     

Experience of Using Manganese-Containing Materials in Blast-Furnace Charge

Metallurgist - The paper discusses the experience gathered at the Yenakievo metallurgical plant and Dnepr metallurgical complex with respect to using manganese-containing materials in the...     

A Nanophotonic Structure Containing Living Photosynthetic Bacteria

Photosynthetic organisms rely on a series of self‐assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna–Matthews–Olson complex to the reaction center. Here, it is shown that by placing living Chlorobaculum tepidum bacteria within a photonic microcavity, the strong exciton–photon coupling regime between a confined cavity mode and exciton states of the chlorosome can be accessed, whereby a coherent exchange of energy between the bacteria and cavity mode results in the formation of polariton states. The polaritons have energy distinct from that of the exciton which can be tuned by modifying the energy of the optical modes of the microcavity. It is believed that this is the first demonstration of the modification of energy levels within living biological systems using a photonic structure.     

Overview and Future Trends of Shrinkage Research

Non-structural cracking of concrete is a serious problem and the underlying phenomena, namely, shrinkage and creep, need to be better understood. Much research has been devoted to this complex problem. However, despite major successes, the phenomenon of shrinkage is still far from being fully understood. The paper discusses the main aspects of concrete shrinkage, with a focus on autogenous and drying shrinkage, which are especially important in high-strength and normal-strength concretes, respectively. These aspects include the theories of physical mechanism, prediction models and future research trends.Shrinkage of concrete due to (a) moisture changes, which result in surface and capillary tension, movement of interlayer water and disjoining pressure and (b) chemical reactions (hydration/dehydration shrinkage, thermal shrinkage, crystallization swelling, carbonation shrinkage and phase transition shrinkage, is reviewed. Many of these mechanisms often cannot be directly linked to the macroscopically observed dilatation/contraction. In some case, volume changes due to chemical reactions influence porosity and degree of saturation. Most chemically induced volume changes are affected by temperature, since chemical reactions are generally accelerated by the temperature elevation and slowed down by the temperature reduction. An overview of recent model developments is presented. Shrinkage reduction methods (cement modification, using admixtures and fibers, proper mix design, methods of internal curing) are discussed.     

NIR-red reflectance-based algorithms for chlorophyll-a estimation in mesotrophic inland and coastal waters: Lake Kinneret case study

A variety of models have been developed for estimating chlorophyll-a (Chl-a) concentration in turbid and productive waters. All are based on optical information in a few spectral bands in the red and near-infra-red regions of the electromagnetic spectrum. The wavelength locations in the models used were meticulously tuned to provide the highest sensitivity to the presence of Chl-a and minimal sensitivity to other constituents in water. But the caveat in these models is the need for recurrent parameterization and calibration due to changes in the biophysical characteristics of water based on the location and/or time of the year. In this study we tested the performance of NIR-red models in estimating Chl-a concentrations in an environment with a range of Chl-a concentrations that is typical for coastal and mesotrophic inland waters. The models with the same spectral bands as MERIS, calibrated for small lakes in the Midwest U.S., were used to estimate Chl-a concentration in the subtropical Lake Kinneret (Israel), where Chl-a concentrations ranged from 4 to 21 mg m⁻³ during four field campaigns. A two-band model without re-parameterization was able to estimate Chl-a concentration with a root mean square error less than 1.5 mg m⁻³. Our work thus indicates the potential of the model to be reliably applied without further need of parameterization and calibration based on geographical and/or seasonal regimes.     

‘Non-solvent’ heat resistant binders: rheology of blends of oligoimides with liquid oligomers

The rheology of binders based on blends of powdery oligoimides with liquid epoxy and acrylic oligomers was studied for a broad interval of concentrations, temperatures and shear rates. It was shown, that prehistory of blends, phase organization of a system and the extent of approaching the equilibrium state determine the rheological behavior of blends. At equilibrium, depending on the state variables, the investigated blends can be single-phase or two-phase. Furthermore, the coexisted phases are not uniform and are characterized by a complex supermolecular structure of composites. In some cases the original blends have not sufficient time to reach the equilibrium state by the beginning of the rheological test, and the system structure evolution to the equilibrium occurs during the experiment. In terms of rheology some structural transformations act in the same direction and the others act in the opposite direction promoting simultaneously both an increase and a decrease in viscosity, affecting the rheological behavior of the system. The experimental dependence of rheological parameters can be explained within the framework of the following conception: structural transformations have thermodynamic nature, they are kinetically controlled and, depending on external factors, can proceed sequentially and/or simultaneously, at the molecular, supermolecular, phase and morphological levels.The resulting data allowed determination of the most perspective compositions of binders based on oligoimides and liquid ‘temporary’ plasticizers as well as the optimal processing conditions.     

Large eddy simulation of two-dimensional isotropic turbulence

Large eddy simulation (LES) of forced, homogeneous, isotropic two-dimensional (2D) turbulence in the energy transfer subrange is the subject of this paper. A difficulty specific to this LES and its subgrid scale (SGS) representation is in that the energy source resides in high wave number modes excluded in simulations. Therefore, the SGS scheme in this case should assume the function of the energy source. In addition, the controversial requirements to ensure direct enstrophy transfer and inverse energy transfer make the conventional scheme of positive and dissipative eddy viscosity inapplicable to 2D turbulence. It is shown that these requirements can be reconciled by utilizing a two-parametric viscosity introduced by Kraichnan (1976) that accounts for the energy and enstrophy exchange between the resolved and subgrid scale modes in a way consistent with the dynamics of 2D turbulence; it is negative on large scales, positive on small scales and complies with the basic conservation laws for energy and enstrophy. Different implementations of the two-parametric viscosity for LES of 2D turbulence were considered. It was found that if kept constant, this viscosity results in unstable numerical scheme. Therefore, another scheme was advanced in which the two-parametric viscosity depends on the flow field. In addition, to extend simulations beyond the limits imposed by the finiteness of computational domain, a large scale drag was introduced. The resulting LES exhibited remarkable and fast convergence to the solution obtained in the preceding direct numerical simulations (DNS) by Chekhlovet al. (1994) while the flow parameters were in good agreement with their DNS counterparts. Also, good agreement with the Kolmogorov theory was found. This LES could be continued virtually indefinitely. Then, a simplified SGS representation was designed, referred to as the stabilized negative viscosity (SNV) representation, which was based on two algebraic terms only, negative Laplacian and positive biharmonic ones. It was found that the SNV scheme performed in a fashion very similar to the full equation and it was argued that this scheme and its derivatives should be applied for SGS representation in LES of quasi-2D flows.     

Typical Fluidization Characteristics for Geldart's Classification Groups

This article describes a comprehensive experimental analysis that defines typical fluidization characteristic curve for Geldart's classification groups. Geldart defined four types of materials which differ by the cohesion forces between particles. An experimental apparatus containing fluidized beds of four pipe diameters and fully controlled by LabVIEW was used to perform the fluidization tests. All tests were performed automatically by gradually increasing the air velocity and measuring the pressure drop over the bed. For each test, the fluidization curve was recorded and the minimum fluidization, bubbling, and slugging velocities were defined. It was found that the fluidization curve of material define accurately the Geldart's group to which the material belongs. In addition, was reviewed the reason for those materials and under which conditions the pressure drop increases in the slugging state. Finally, the influence of height to bed diameter H/D ratio on the shape of characterization curve was found. The present study has significant interest for researchers and designers since it enables to predict the fluidization characteristics of two-phase (fluid-solids) flows.