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.     

Stimulus‐Responsive Anti‐Oxidizing Drug Crystals and their Ecological Implication

Various antioxidants are being used to neutralize the harmful effects of reactive oxygen species (ROS) overproduced in diseased tissues and contaminated environments. Polymer‐directed crystallization of antioxidants has attracted attention as a way to control drug efficacy through molecular dissolution. However, most recrystallized antioxidants undertake continuous dissolution independent of the ROS level, thus causing side‐effects. This study demonstrates a unique method to assemble antioxidant crystals that modulate their dissolution rate in response to the ROS level. We hypothesized that antioxidants recrystallized using a ROS‐labile polymer would be triggered to dissolve when the ROS level increases. We examined this hypothesis by using catechin as a model antioxidant. Catechin was recrystallized using polyethylenimine cross‐linked with ROS‐labile diselanediylbis‐(ethane‐2,1‐diyl)‐diacrylate. Catechin crystallized with the ROS‐labile polymer displays accelerated dissolution proportional to the H₂O₂ concentration. The ROS‐responsive catechin crystals protect vascular cells from oxidative insults by activating intracellular glutathione peroxidase expression and, in turn, inhibiting an increase in the intracellular oxidative stress. In addition, ROS‐responsive catechin crystals alleviate changes in the heart rate of Daphnia magna in oxidative media. We propose that the results of this study would be broadly useful for improving the therapeutic efficacy of a broad array of drug compounds.     

Molecular engineering of Diketopyrrolopyrrole-based photosensitizer for solution processed small molecule bulk heterojunction solar cells

New symmetrical low band-gap small molecule materials, DPP-bis[ter-3HT-TPA] and DPP-bis[ter-3HT] as novel derivatives of Diketopyrrolopyrrole-thiophene with/without triphenylamine (TPA) end group have been synthesized and characterized. And the effects of TPA moiety were investigated. Compared to DPP-bis[ter-3HT], DPP-bis[ter-3HT-TPA] shows red-shifted absorption and significantly higher molar absorption coefficient. And the HOMO level of DPP-bis[ter-3HT-TPA] is elevated than DPP-bis[ter-3HT]. Moreover, DPP-bis[ter-3HT-TPA] exhibited one order higher hole mobility than DPP-bis[ter-3HT], suggesting that TPA contributes to a better hole mobility. The bulk-heterojunction photovoltaic devices with DPP-bis[ter-3HT-TPA] showed better efficiencies than DPP-bis[ter-3HT], showing the best power-conversion efficiency (PCE) of 1.5% (±0.12) under 100 mW/cm² with a short-circuit current (J_sc)=5.73 mA/cm², a fill factor (FF)=0.45, and an open-circuit voltage (V_oc)=0.59 mV.     

Synthesis,Characterization, and Thermoelectric Properties of Electrospun Boron-Doped Barium-Stabilized Bismuth-Cobalt Oxide Nanoceramics

In this study, the boron-doped barium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by the polymeric precursor technique. The powders were characterized by X-ray diffraction, scanning electron microscopy, and the physical properties measurement system. The X-ray diffraction results showed that these patterns have mixture of two phases as face-centered cubic and body-centered cubic. Values of the crystallite size, the dislocation density, and the microstrain were calculated by the Scherrer equation. According to these values, the crystallite size decreased from 60 to 51 nm with the boron addition in the boron-undoped and boron-doped samples, respectively. The scanning electron microscope results showed that nanograins are rarely seen in the boron-undoped samples, but nanograins turn into needle-like and layered structures with boron addition. The diameters distribution of nanofibers was calculated. The average diameter of the boron-doped sample is smaller than the boron-undoped sample. The physical properties measurement system values showed that the electrical and thermal conductivity, the Seebeck coefficient, and the figure of merit increased with the temperature rise for both samples. The boron-doping effect increased the electrical and thermal conductivity, decreased the Seebeck coefficient, and decreased the figure of merit.     

Capacity-fading prediction of lithium-ion batteries based on discharge curves analysis

We have developed a new technology to predict capacity fading of lithium-ion cells using the analysis of their discharge curves. A cell capacity is deduced from the cell voltage window and the cell discharge curve, which was obtained by superimposing discharge curves of the positive and negative electrodes. This new technology consists of three steps: first, to analyze cell discharge curves measured during the calendar life test in order to evaluate deterioration indicators such as the positive and negative usable capacities and the irreversible capacities caused by the side reactions; secondly, to formulate these indicators as the functions of the test time; lastly, to produce the cell discharge curves by using these functions and deduce corresponding cell capacity, over storage days for prediction.Prediction of the faded capacities of the cells after a 960 day calendar life test was attempted with the data up to 360 days using the technology described above and the conventional method by extrapolating capacity-fading data in accordance with square-root time rule. Consequently, the proposed technology predicted the faded capacities more precisely than the conventional method, particularly under severe conditions.     

Tailored electrostrain and related properties in (1 − x)BaTiO3–xSrSnO3 Pb-free electroceramics

We report excellent electrostrain properties of (1 − x)BaTiO₃–xSrSnO₃ (BSTS) Pb-free electroceramics (0 ≤ x ≤ 0.15), as well as the corresponding structural, dielectric, and ferroelectric properties. A tailored phase diagram of the pseudo-binary solid solution of BaTiO₃–SrSnO₃, which exhibits a nearly composition-independent orthorhombic–tetragonal polymorphic phase boundary close to room temperature, was obtained, and, in contrast to Ba(Ti_1−xSn_x)O₃, the appearance of the relaxor mode was accelerated in the phase transition of BSTS owing to the additional incorporation of Sr. Using these compositionally modified phase-related characteristics, desirable sets of electrostrain properties for actuator applications were obtained. Based on these results, we propose that BSTS is a promising candidate for Pb-free electroceramics for high-precision actuator applications near room temperature.