Transmission loss caused by an angular misalignment between two multimode fibers with arbitrary profile exponents

The coupling efficiency between two multimode fibers with an angular misalignment is calculated. For the practically interesting cases of parabolic and step-index profiles, closed-form expressions and simple approximations are derived. Furthermore a general loss formula for small tilt angles and arbitrary profile exponents is presented.     

Automated formal analysis and verification: an overview

This paper provides an overview of various existing approaches to automated formal analysis and verification. The most space is devoted to the approach of model checking, including its basic principles as well as the different techniques that have been proposed for dealing with the state space explosion problem in model checking. This paper, however, includes a brief discussion of theorem proving and static analysis too. All of the discussed approaches are introduced mostly on an informal level, with an attempt to provide the reader with their basic ideas and references to works where more details can be found.     

Gas sensing properties of nanocrystalline diamond films

Toxic gas sensing device with metal electrodes built into nanocrystalline diamond (NCD) is investigated. The NCD morphology is controlled via seeding and/or deposition time. The surface properties and morphology of NCD are studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). AFM measurements reveal increase in NCD surface area by up to 13%. Gas sensing properties of H-terminated NCD device show high sensitivity towards oxidizing species where the surface conductivity is increased by an order of magnitude for humid air and by three orders of magnitude for COCl₂. The surface conductivity exhibits a small decrease to reducing spices (CO₂, NH₃).     

The xanthate method of grafting. X. Grafting of acrylamide onto very-high-yield chemithermomechanical birch and aspen pulps

Hardwood pulp (birch: Betula Papyfera Marsh, and aspen: Populus Tremolides Michx) has been copolymerizeed with acrylamide using the xanthate grafting method. Grafting has been initiated using a redox system of ferrous ion and hydrogen peroxide. The effect of operating conditions on grafting parameters was also investigated. The factors studied were initial pH, time, and concentrations of hydrogen peroxide and acrylamide. When birch was used as a substrate, grafting parameters were as follows: grafting efficiency 82%, degree of conversion 35%, and polymer loading 60%. In the case of aspen, the maximum level of grafting efficiency, i.e., 87%, was reached with a polymer loading of 60%. Nevertheless, as in the case of birch, the conversion reached a rather low-level reading, i.e., 50%. Finally, some mechanical properties of paper sheets obtained through grafted pulps (dry and wet breaking lengths, dimensional stability, modulus, and extension at break) are compared to those of standard paper sheets.     

Tensile behavior of staple fiber yarns,part IV: experimental verification of predicted stress–strain curves

In this paper, specific stress–strain curves were predicted for viscose, cotton, and polyester yarns spun by ring and rotor technologies. The average fiber-specific stress–strain curves were used to predict yarn-specific stress–strain curves. The predicted yarn-specific stress–strain curves captured the experimental yarn-specific stress–strain curves well both in shape and position for the three studied yarn types. However, higher prediction error was observed relatively in polyester yarns due to more slippage of fibers in these yarns. All rotor yarns exhibited higher difference between experimental and predicted results which might be the result of the nature of the twist in rotor yarn.     

Tensile behavior of staple fiber yarns part III: comparison of mathematical models

Despite the development of artificial neural network and computer simulation models that predict yarn tensile properties, the mathematical model is still very important being the base for all models. In this research, three mathematical models have been applied for evaluation of coefficient of fiber strength utilization in staple spun yarns before break at same value of yarn strains. The experiments were conducted on cotton, viscose and polyester fibers, and yarns. The results indicated that our model exhibited least prediction error followed by Pan’s and Frydrych’s models for cotton and viscose but for polyester, Pan’s model produced least error followed by Frydrych’s model and our model. The superiority of our model might be resulted from the introduction of the phenomena of fiber directional distribution in the staple spun yarns.     

bOptimizing atomic force microscopy for characterization of diamond-protein interfaces

Atomic force microscopy (AFM) in contact mode and tapping mode is employed for high resolution studies of soft organic molecules (fetal bovine serum proteins) on hard inorganic diamond substrates in solution and air. Various effects in morphology and phase measurements related to the cantilever spring constant, amplitude of tip oscillations, surface approach, tip shape and condition are demonstrated and discussed based on the proposed schematic models. We show that both diamond and proteins can be mechanically modified by Si AFM cantilever. We propose how to choose suitable cantilever type, optimize scanning parameters, recognize and minimize various artifacts, and obtain reliable AFM data both in solution and in air to reveal microscopic characteristics of protein-diamond interfaces. We also suggest that monocrystalline diamond is well defined substrate that can be applicable for fundamental studies of molecules on surfaces in general.     

Proposed EU legislation to force changes in sewage sludge disposal: A case study

The consequences of changes planned in the European Union legislation relevant to the disposal of sewage sludges are discussed. A specific municipal waste water treatment plant is analyzed in terms of drying and subsequent combustion or pyrolysis of the produced stabilized sludge, and the respective net energy balances are carried out. A simplified economic analysis of the two disposal options is presented, which suggest that combustion of the sludge would be economically infeasible while pyrolysis of the sludge in a modular, self-sufficient container unit can bring a small financial benefit due to the selling of the produced phosphorus-rich biochar.

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Effects of processing variables on the mechanical properties of compression molded polystyrene-wood fiber composites

Optimization of mixing and molding conditions (e.g. temperature, time and pressure) of aspen chemithermomechanical pulp (CTMP)-polystyrene composites was carried out. Compounding conditions showed a substantial effect on the mechanical properties of the composites. The effect of fiber encapsulation with polystyrene on the mechanical properties of the composites was also evaluated. Compared to non-encapsulated ones, the mechanical properties of composites showed superior results when encapsulated CTMP fibers were used. After encapsulation of wood fibers, and optimization of mixing and molding conditions, composites with up to 36% of fiber volume fraction could be incorporated in polystyrene with improved mechanical properties.