Hexaferrite/Polyester Composite Coatings for Electromagnetic-Wave Absorbers

Composite coatings, consisting of a ceramic barium hexaferrite and polyester, were manufactured by atmospheric plasma spraying. The crystalline structure of the barium hexaferrite was preserved during the spraying process while the polyester first (partly) melted and then resolidified. The high magnetic losses of the barium hexaferrite at mm-waves were coupled to the dielectric losses of the polyester in the composite coating and the superior electromagnetic absorption of the composite coating with respect to the pure materials was determined.     

Distributed energy generation and sustainable development

Conventionally, power plants have been large, centralized units. A new trend is developing toward distributed energy generation, which means that energy conversion units are situated close to energy consumers, and large units are substituted by smaller ones. A distributed energy system is an efficient, reliable and environmentally friendly alternative to the traditional energy system. In this article, we will first discuss the definitions of a distributed energy system. Then we will evaluate political, economic, social, and technological dimensions associated with regional energy systems on the basis of the degree of decentralization. Finally, we will deal with the characteristics of a distributed energy system in the context of sustainability. This article concludes that a distributed energy system is a good option with respect to sustainable development.     

Pyrolysed 3D‐Carbon Scaffolds Induce Spontaneous Differentiation of Human Neural Stem Cells and Facilitate Real‐Time Dopamine Detection

Structurally patterned pyrolysed three‐dimensional carbon scaffolds (p3D‐carbon) are fabricated and applied for differentiation of human neural stem cells (hNSCs) developed for cell replacement therapy and sensing of released dopamine. In the absence of differentiation factors (DF) the pyrolysed carbon material induces spontaneous hNSC differentiation into mature dopamine‐producing neurons and the 3D‐topography promotes neurite elongation. In the presence and absence of DF, ≈73–82% of the hNSCs obtain dopaminergic properties on pyrolysed carbon, a to‐date unseen efficiency in both two‐dimensional (2D) and 3D environment. Due to conductive properties and 3D environment, the p3D‐carbon serves as a neurotransmitter trap, enabling electrochemical detection of a significantly larger dopamine fraction released by the hNSC derived neurons than on conventional 2D electrodes. This is the first study of its kind, presenting new conductive 3D scaffolds that provide highly efficient hNSC differentiation to dopaminergic phenotype combined with real‐time in situ confirmation of the fate of the hNSC‐derived neurons.     

Modelling of airborne dust emissions in CNC MDF milling

All dust control measures are necessary to reduce dust exposure in MDF (Medium Density Fibreboard)-milling, because of the high amount and fineness of the dust produced and a potential risk of exposure to formaldehyde or other glue chemicals during the machining of MDF. The most effective way of reducing dust exposure is to reduce the emission of dust at the source. Airborne dust emission was studied and modelled in the milling. In the milling of MDF, airborne dust emission was much higher than in the milling of solid materials. Milling of MDF produced airborne particles with a mass median diameter of 6–7 µm. The most significant factor affecting the amount of dust created from milling was average chip thickness. In order to reduce the amount of dust, milling parameters should be chosen so that the average chip thickness is greater than 0.05 mm. The average chip thickness could be obtained with different milling parameters, for example with different combinations of feed and traverse rates. The same chip thicknesses resulted in around the same percentage fraction of fine dust mass regardless of how the average chip thickness was obtained. The relationship between the percentage fraction of fine dust mass from the removed mass (c_%) and the chip thickness (h_m) was modelled and presented in the form of c_% = 0.194 h _m ^-1. The model developed can be used to estimate the percentage fraction of fine dust mass as a function of chip thickness. The model can be used in optimisation programs for CNC milling machines to minimize the airborne dust generated and to reduce dust exposure.     

Cartesian authentication codes from functions with optimal nonlinearity

In this paper, we present several classes of authentication codes using functions with perfect nonlinearity and optimum nonlinearity. Some of the authentication codes are optimal. On the other hand, these authentication codes are easy to implement due to their simple algebraic structures.     

Bayesian object matching

Matching of object refers to the problem of inferring unknown co-occurrence or alignment between observations or samples in two data sets. Given two sets of equally many samples, the task is to find for each sample a representative sample in the other set, without prior knowledge on a distance measure between the sets. Given a distance measure, the problem would correspond to a linear assignment problem, the problem of finding a permutation that re-orders samples in one set to minimize the total distance. When no such measure is available, we need to consider more complex solutions. Typical approaches maximize statistical dependency between the two sets, whereas in this work we present a Bayesian solution that builds a joint model for the two sources. We learn a Bayesian canonical correlation analysis model that includes a permutation parameter for re-ordering the samples in one of the sets. We provide both variational and sampling-based inference for approximative Bayesian analysis, and demonstrate on three data sets that the resulting methods outperform the earlier solutions.     

On the effect of a spherical shield on the radiation Q and efficiency of ideal dipole antennas

A method is developed for calculating the radiation efficiency and quality factor, Q, for azimuthally symmetric electric (Tm) and magnetic (Te) multipole fields surrounded by a semi-transparent spherical shield of variable thickness, dielectric and magnetic constants involving losses. A matrix method is used to connect the transverse field components at adjacent interfaces. The Q and efficiency are determined by computing the energy stored in the near field of the multipole as well as the power radiated and dissipated in the shield. A numerical comparison of the performance of electric and magnetic dipole radiators is given as a function of frequency. An expression is derived for the permittivity of the shield which optimisés the Q.     

Association of lumbar artery narrowing, degenerative changes in disc and endplate and apparent diffusion in disc on postcontrast enhancement of lumbar intervertebral disc

Objective  A decreased supply of nutrition to the intervertebral disc can lead to disc degeneration. Nutrient supply can be simulated in vivo by measuring gadolinium enhancement of the disc. We aimed to study the changes associated with disc degeneration that may have effect on the nutrition of the disc, i.e. lumbar artery narrowing, Modic changes, endplate defects, and apparent diffusion coefficient (ADC) in nucleus pulposus. Patients and methods  Twenty male volunteers underwent a lumbar spine examination at 1.5 T for anatomical imaging, diffusion weighted imaging, magnetic resonance angiography, and for T1 relaxation time quantification of contrast enhancement of intervertebral disc. Results  Enhancement of the disc increased with degeneration. Disc space narrowing associated strongly with the enhancement (Pearson’s correlation coefficient 0.46, P < 0.001). The enhancement rate in discs adjacent to Modic type 2 changes was 24%, adjacent to type 1/2 changes 58%, and 13% in the absence of Modic changes. Discs adjacent to endplate defects enhanced 32% compared to 10% of normal endplates. Lumbar artery narrowing or ADC in the disc were not associated with the enhancement. Conclusion  Increased enhancement of a degenerated disc is associated mostly with disc space narrowing and with the presence of degenerative endplate changes and endplate defects.     

Embedding impedance of a millimeter wave Schottky mixer: Scaled model measurements and computer simulations

Using scaled model measurements at 2.5–12 GHz the embedding network of a 3 mm Schottky diode mixer has been developed. The noise performance of a cryogenic millimeter wave receiver was simulated by computer applying the developed equivalent circuit and diode parameters. The effects of impedance match at the fundamental frequency as well as at harmonic frequencies were studied. Also the effect of diode I-V-curve steepness was studied. The calculated results were compared with the experimental noise performance.