Physical and regulatory constraints for communication over the power supply grid

This article describes the topology of the power supply network in respect to the deployment of power line communications in different countries. The characteristics of the power line channel are investigated, and the causes of electromagnetic interference from PLC technology in wireless communications services are discussed. Since the radiation originating from PLC cannot be avoided completely by technical means, a solution via standardization is necessary. The current status of worldwide regulation concerning EMC is presented.     

Theory-based improvements of continuous polymer fractionation demonstrated for poly(carbonate)

For the first time, a quantitative theoretical analysis (liquid/liquid phase equilibria treated by means of the continuous thermodynamics) of the operating characteristics of continuous polymer fractionation (CPF) was performed. The results of these calculations were compared with data published for CPF of polyethylene. It turned out that the efficiency of the conventional CPF corresponds to approximately two theoretical plates only. For this reason, several improvements, suggested by theoretical considerations, were realized experimentally, for which purpose the system dichloromethane/diethylene glycol/bisphenol-A polycarbonate was chosen. The pulsating sieve-bottom column was replaced by a nonpulsating column filled with glass beads. In this manner, the number of theoretical plates could be raised considerably. A further improvement of the fractionation efficiency results from the reflux of part of the polymer contained in the sol phase. In praxi, this situation was realized by putting a condensor on top of the column and introducing the feed somewhere near its upper third. After predictive calculations and orienting experiments, 125 g of a polycarbonate with M_w = 29 kg/mol and a nonuniformity U = 1.3 were fractionated in four consecutive CPF runs (where the gels were directly used as feed for the next step) into five fractions of approximately equal weight. Except for the lowest-molecular-weight fraction, one obtains nonuniformities on the order of 0.1.     

Kinetics of Z-Phase Precipitation in 9 to 12 pct Cr Steels

The Z-phase nitride is seen as a detrimental phase in 9 to 12 pct Cr steels as it is in competition with the beneficial MX particles. Two model steels, with 9 pct Cr and 12 pct Cr content, respectively, were designed to study the effect of Cr on Z-phase precipitation kinetics. The steels were isothermally aged at 873 K, 923 K, and 973 K (600 °C, 650 °C, and 700 °C) for up to 30,000 hours in order for Z-phase to replace MX. X-ray diffraction (XRD) analysis of extracted precipitates was used to quantitatively follow the evolution of the nitrides population. It was found that the 12 pct Cr steel precipitated Z-phase 20 to 50 times faster than the 9 pct Cr steel. Transmission electron microscopy (TEM) was applied to follow the Z-phase precipitation, using energy-dispersive X-ray spectroscopy (EDS) line scans and atomic resolution imaging.     

Glycerol monocaprate (monocaprin) reduces contamination by Escherichia coli and Salmonella enteritidis on hard surfaces

Emulsions of glycerol monocaprate (monocaprin) kill a variety of pathogenic bacteria and viruses in suspension. In this study the microbicidal activity of monocaprin against enterobacteria was tested on contaminated hard surfaces. Surfaces were contaminated with nutrient broth or meat juice containing large numbers of Escherichia coli or Salmonella enteritidis. They were then treated with acidified monocaprin emulsions and the surviving bacteria counted. Monocaprin killed S. enteritidis in chicken meat juice on plastic cutting boards and reduced the number of viable E. coli and S. enteritidis by more than 5 log₁₀ in 2 min on a laminated plastic kitchen counter contaminated with nutrient broth. Monocaprin rapidly killed E. coli on glass, stainless steel, laminated plastic, glazed ceramic tiles and polypropylene boards. It was most effective on glass and stainless steel and more effective on dry than on wet surfaces. It was concluded that acidified monocaprin emulsions reduce contamination by pathogenic enterobacteria on hard surfaces. They may be useful as sanitizers in the home, and possibly in public places, where contaminated surfaces are a potential source of transmission of pathogens to humans. Cleaning with monocaprin emulsions may therefore be a means to improve hygiene and infection control.     

Berichtigung

Ohne Zusammenfassung The online version of the original article can be found at     

Matrix assignment with individual weights and selected controller restrictions

The design method of matrix assignment as a generalization of pole assignment is extended with some special features. Overstepping the optimal solution given by the Penrose point could be needed in the case of unstable plants. Individual weighting of the coefficient matrix differences is carried out and oriented on the numerical importance of the settings. Individual restrictions of the controller matrix are also included and are based on the given deterioration of state variables with noise. The paper also addresses minimum values of the controller norm which are located between singular values of the input matrix of the system.     

Functionalization of Polymer Surfaces Using Excimer VUV Systems and Silent Discharges. Application to Electroless Metallization

New approaches for electroless plating of nonconductive polymers or polymer-based materials are described. In this work, polyimide substrates were surface-functionalized (i) in nitrogenated (ammonia at reduced pressure) and oxygenated (air at atmospheric pressure) atmospheres under assistance of vacuum-ultraviolet (VUV) irradiation (use of a xenon silent discharge excimer source) or (ii) directly in air at atmospheric pressure using a dielectric-barrier discharge (DBD) device. After functionalization, the substrates were “activated” by dipping in a dilute acidic PdCl₂ solution or by spin-coating of a thin metal-organic film (from a solution of palladium acetate (PdAc) in chloroform). The catalytic activity of the so-deposited palladium species toward the electroless deposition of nickel was studied before and after a VUV post-irradiation (in air at atmospheric or reduced pressure) with a view to understanding better the role of the reducer (sodium hypophosphite) within the electroless bath.

This work confirms the specific interest of grafting nitrogenated functionalities onto polymer surfaces for attaching covalently the palladium-based catalyst (in particular in the case of the PdCl₂ route), forming thus strong Pd - N - C bonds at the metal/polymer interface. This results from the strong chemical affinity of palladium toward nitrogen. On the other hand, when oxygenated functionalities are surface-grafted, the conventional two-step procedure using SnCl₂ and PdCl₂ solutions can be proposed due to the strong chemical affinity of tin toward oxygen. The Ni deposits obtained under these different conditions pass the standard Scotch^®-tape test and, therefore, exhibit a good practical adhesion. For this same purpose, it is interesting to note that the DBD treatment operating in air at atmospheric pressure causes an increase of the surface roughness and, therefore, an improvement in adhesion of metallic films when their initiation is catalyzed through the PdAc route. In addition, this work demonstrates that extensive research still has to be performed to understand and improve the Ni/polymer adhesion when the PdAc route associated with a VUV irradiation is considered.     

Particulate-Reinforced Precursor-Derived Si–C–N Ceramics: Optimization of Pyrolysis Atmosphere and Schedules

Surface oxidation occurred during pyrolysis of SiC particulate-reinforced composites (PRCs) with a precursor-derived Si–C–N matrix. In contrast, such an oxidation was not observed in pure Si–C–N ceramics. The present investigation discusses the possible reasons for this, and reports on the influence of such an oxidation on the microstructure and the mechanical and thermal properties of PRCs by the precursor-impregnation and pyrolysis method. The high-temperature mass stability of the PRCs in Ar deteriorated owing to the decomposition of SiO₂ formed by oxidation. The effects of the pyrolysis schedule on the processing and mechanical properties of PRCs are also investigated.