Milk-based beverages obtained by Kombucha application

This paper investigates the manufacture of milk-based beverages by application of several Kombucha starters. Local Kombucha culture was grown up on three substrates: sweetened black and green tea, and topinambur. Their concentrates were obtained by vacuum-evaporation and amounts of 10% and 15% (v/v) were applied to milk (2.2% fat). The traditional yoghurt starter (B3) was applied for producing control samples. All fermentations were stopped when the pH reached 4.4. Fermentation curves were registered, linear for yoghurt and sigmoidal for Kombucha. Two times faster process was achieved with yoghurt starter. Influence of inoculum concentration on the rate of fermentation was insignificant. Viscosities were higher for Kombucha beverages at lower speeds of spindle, but lower at higher speeds of spindle. Very high sensory scores were achieved for all beverages, after production and after 5-days’ storage.     

Unsupervised learning with hierarchical feature selection for DDoS mitigation within the ISP domain

A new Mirai variant found recently was equipped with a dynamic update ability, which increases the level of difficulty for DDoS mitigation. Continuous development of 5G technology and an increasing number of Internet of Things (IoT) devices connected to the network pose serious threats to cyber security. Therefore, researchers have tried to develop better DDoS mitigation systems. However, the majority of the existing models provide centralized solutions either by deploying the system with additional servers at the host site, on the cloud, or at third party locations, which may cause latency. Since Internet service providers (ISP) are links between the internet and users, deploying the defense system within the ISP domain is the panacea for delivering an efficient solution. To cope with the dynamic nature of the new DDoS attacks, we utilized an unsupervised artificial neural network to develop a hierarchical two‐layered self‐organizing map equipped with a twofold feature selection for DDoS mitigation within the ISP domain.     

Calculation method for estimating thermal impedance for pulse current of power semiconductor devices

Contents The described method is valid for arbitrary wave forms of the constant pulse current and for all diode, transistor and thyristor family devices whose thermal circuit can be modelled electrically by the serial connection of resistor-capacitor RC-pairs and whose forward characteristic can be approximated by slope resistance and threshold voltage. Temperature dependence of the device's thermal circuit parameters and temperature dependence of the forward characteristic parameters were not taken into consideration. The method enables an estimate to be made of the influence of current amplitude on the value of thermal impedance for pulse current.

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Eine Rechnungsmethode zur Bewertung der thermischen Impedanz für Impulsstrom von Leistungshalbleiterkomponenten

Übersicht Die vorgestellte Methode ist für beliebige Impulsstromform und zwar für alle Komponenten aus den Dioden-, Transistoren- und Thyristoren-Familien geeignet, deren thermischen Kreis man durch Serienschaltung von RC-Gliedern elektrisch modellieren und die Durchlaßkennlinie durch Ersatzwiderstand und Schleusenspannung approximieren kann. Die Temperaturabhängigkeit der Parameter der Durchlaßkennlinie der Komponente wird nicht berücksichtigt. Die Methode erlaubt eine Abschätzung des Einflusses der Stromamplitude auf die thermische Impedanz für Impulsstrom.

     

The structure characterization of thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) hydrogel

The goal of this work was to investigate a possible way of crosslinking polymer chains and the potential formation of intramolecular hydrogen bonds in thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) (p(NIPAM‐HPMet)) hydrogels obtained by radical polymerization. The chemical structure of the synthesized hydrogels was investigated by Fourier transform infrared (FTIR) spectroscopy and XRD. The FTIR spectrum confirmed the presence of hydrogen bonds formed between the chains in the copolymer. XRD analysis confirmed the amorphous ? crystalline structure of the copolymer. A three‐glass transition and two melting temperatures were detected by DSC. It was found that the addition of HPMet increased the glass transition and melting temperatures of the p(NIPAM‐HPMet) copolymer. The swelling transport mechanism of p(NIPAM‐HPMet) changed from non‐Fickian at 20 °C to case III or zero‐order time‐independent kinetics characterized by a linear mass uptake with time with increasing temperature at 40 °C. © 2013 Society of Chemical Industry     

Nonlinear frequency response method for estimation of single solute adsorption isotherms. Part II

The aim of this paper is to investigate the possibility of applying a nonlinear frequency response (FR) method described by Ili? et al. [2007b. Nonlinear frequency response method for estimation of single solute adsorption isotherms. Part I. Theoretical basis and simulations, this volume, doi:10.1016/j.ces.2007.05.004] to determine single solute adsorption isotherms. The method is based on the analysis of the nonlinear FR of a chromatographic column to a periodical change of the inlet concentration around several steady-state concentrations. The first, second and third local derivatives of single solute isotherms are estimated from the low-frequency asymptotic behaviour of the corresponding FR functions. The adsorption of 4-tert-butylphenol and ethyl benzoate as single solutes is studied on octadecyl silica (C₁₈) from methanol-water mixture (60:40). Experiments are performed using a standard gradient HPLC unit capable to realize inlet concentration changes in a nearly sine waveform. Small injections of compounds into the not preloaded column, as well as conventional frontal analysis experiments are performed for rough estimation of the adsorption isotherm coefficients and comparison with the results obtained using the nonlinear FR method.     

The number of spanning trees of a graph with given matching number

The number of spanning trees of a graph G is the total number of distinct spanning subgraphs of G that are trees. In this paper, we present sharp upper bounds for the number of spanning trees of a graph with given matching number.     

Trees with minimal Laplacian coefficients

Let $G$ be a simple undirected graph with the characteristic polynomial of its Laplacian matrix $L\left(G\right)$, $P(G,\mu )={\sum }_{k=0}^n{(?1)}^k{c}_k{\mu }^{n?k}$. It is well known that for trees the Laplacian coefficient $c_{n?2}$ is equal to the Wiener index of $G$, while $c_{n?3}$ is equal to the modified hyper-Wiener index of the graph. In this paper, we characterize $n$-vertex trees with given matching number $m$ which simultaneously minimize all Laplacian coefficients. The extremal tree $A(n,m)$ is a spur, obtained from the star graph $S_{n?m+1}$ with $n?m+1$ vertices by attaching a pendant edge to each of certain $m?1$ non-central vertices of $S_{n?m+1}$. In particular, $A(n,m)$ minimizes the Wiener index, the modified hyper-Wiener index and the recently introduced Incidence energy of trees, defined as $IE\left(G\right)={\sum }_{k=0}^n\sqrt{{\mu }_k}$, where ${\mu }_k$ are the eigenvalues of signless Laplacian matrix $Q\left(G\right)=D\left(G\right)+A\left(G\right)$. We introduced a general $\rho$ transformation which decreases all Laplacian coefficients simultaneously. In conclusion, we illustrate on examples of Wiener index and Incidence energy that the opposite problem of simultaneously maximizing all Laplacian coefficients has no solution.     

Electrical and elastic properties of Cu-W graded material produced by vibro compaction

Self-formed W graded preform was produced by size segregation of weakly vibrated tungsten bimodal granular medium. The bimodal granular media bed was initially set up with larger W agglomerates placed on the bottom and with smaller agglomerates on the top of the container. During the vibro-compaction treatment the granular bed progresses through three distinguished compaction stages: percolation, diffusion like or hopping, and non-equilibrium steady state, which exhibit different packing factor and structures. Shorter vibration time results in a skeleton type of microstructure, while a graded structure was formed when the system reaches a non-equilibrium steady state. The vibrated beds were uniaxially pressed to manufacture sintered W preform with a graded interconnected porosity. High temperature sintering treatments complete the evolution of a steeper gradient in porosity predominantly through coalescence process. Electrical and elastic properties of the final materials, produced by infiltration of Cu into the sintered W preforms, are strongly influenced by the W microstructural evolution. It has been shown that the optimal microstructure for electrical properties consists of a highly 3D interconnected Cu phase (skeleton type of microstructure), while the graded structure exhibits higher E-modulus. This work was undertaken to better understand the nature of the graded structure and to study the relationship between the self-formed microstructure types, electrical and elastic materials properties.