A study of concept-based similarity approaches for recommending program examples

This paper investigates a range of concept-based example recommendation approaches that we developed to provide example-based problem-solving support in the domain of programming. The goal of these approaches is to offer students a set of most relevant remedial examples when they have trouble solving a code comprehension problem where students examine a program code to determine its output or the final value of a variable. In this paper, we use the ideas of semantic-level similarity-based linking developed in the area of intelligent hypertext to generate examples for the given problem. To determine the best-performing approach, we explored two groups of similarity approaches for selecting examples: non-structural approaches focusing on examples that are similar to the problem in terms of concept coverage and structural approaches focusing on examples that are similar to the problem by the structure of the content. We also explored the value of personalized example recommendation based on student's knowledge levels and learning goal of the exercise. The paper presents concept-based similarity approaches that we developed, explains the data collection studies and reports the result of comparative analysis. The results of our analysis showed better ranking performance of the personalized structural variant of cosine similarity approach.     

Cationic metalloporphyrins for synthesis of conducting,water-soluble polyaniline

Catalytic oxidative polymerization of aniline was performed using the tetrapyridylporphyrin (TPyP) complexes of iron (III), manganese (III) and cobalt (III). It was found that the cationic metalloporphyrin catalyzed the polymerization of aniline more efficiently than the anionic metalloporphyrins, when using aqueous H₂O₂. The reaction was carried out in the presence of sulfonated polystyrene (SPS) as a template at different pHs, ranging from 1 to 5, and the best results were obtained at pH 2. Formation of water-soluble polyaniline (PANI) was characterized by UV–vis, FT-IR spectroscopy and cyclic voltammetry (CV). FT-IR and UV–vis spectra confirm the formation of the conducting form of PANI. Cyclic voltammetry measurements demonstrate that the polymer has convenient electroactivity.     

In situ synthesized chitosan–gelatin/ZnO nanocomposite scaffold with drug delivery properties: Higher antibacterial and lower cytotoxicity effects

In this work, chitosan–gelatin/zinc oxide nanocomposite hydrogel scaffolds (CS–GEL/nZnO) were prepared via in situ synthesis of ZnO nanoparticles (nZnO) to reach a scaffold with both inherent antibacterial and drug delivery properties. The prepared nanocomposite hydrogel scaffolds were characterized using scanning electron microscopy, transmission electron microscopy, atomic absorption spectrometer, Fourier transform infrared spectroscopy, and X-ray diffraction. In addition, swelling, biodegradation, antibacterial, cytocompatibility, and cell attachment of the scaffolds were evaluated. The results showed that the prepared scaffolds had high porosity with a pore size of 50–400 μm and nZnO were well distributed without any agglomeration on the CS–GEL matrix. In addition, the nanocomposite scaffolds showed enhanced swelling, biodegradation, and antibacterial properties. Moreover, the drug delivery studies using naproxen showed that nZnO could control naproxen release. Cytocompatibility of the samples was proved using normal human dermal fibroblast cells (HFF2). In comparison to the previous reports which nZnO were simply added to the matrix of the scaffold, in situ synthesis of nZnO was led to higher antibacterial and lower cytotoxicity effects as a result of well distribution of nZnO in this method. According to the findings, the in situ synthesized CS–GEL/nZnO is strongly recommended for biomedical applications especially skin tissue engineering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47590.     

Analyzing the capacity of wireless ad hoc networks

In this paper we develop analytical closed form expression for the capacity of a wireless ad hoc network. First, for the general case when nodes can adapt their communication rates to the link quality, a proper formulation for the total network capacity is presented based on the cumulative distribution function (CDF) of the signal to interference power ratio (SIR). Then, a closed form expression for this CDF is analytically derived. This closed form is further studied by fitting it to a normal distribution. Afterwards, the capacity of the network is investigated. By examining the effect of the outage threshold, it is shown that in order to obtain a higher capacity, one may use simple non-adaptive transceivers with higher threshold on the received SIR. These results are obtained by conducting analytical and simulation studies.     

High Surface Area MoS2/Graphene Hybrid Aerogel for Ultrasensitive NO2 Detection

A MoS₂/graphene hybrid aerogel synthesized with two‐dimensional MoS₂ sheets coating a high surface area graphene aerogel scaffold is characterized and used for ultrasensitive NO₂ detection. The combination of graphene and MoS₂ leads to improved sensing properties with the graphene scaffold providing high specific surface area and high electrical and thermal conductivity and the single to few‐layer MoS₂ sheets providing high sensitivity and selectivity to NO₂. The hybrid aerogel is integrated onto a low‐power microheater platform to probe the gas sensing performance. At room temperature, the sensor exhibits an ultralow detection limit of 50 ppb NO₂. By heating the material to 200 °C, the response and recovery times to reach 90% of the final signal decrease to <1 min, while retaining the low detection limit. The MoS₂/graphene hybrid also shows good selectivity for NO₂ against H₂ and CO, especially when compared to bare graphene aerogel. The unique structure of the hybrid aerogel is responsible for the ultrasensitive, selective, and fast NO₂ sensing. The improved sensing performance of this hybrid aerogel also suggests the possibility of other 2D material combinations for further sensing applications.     

Melamine–formaldehyde curing acceleration by TiO2-based silver-white pigments catalysis

European Journal of Wood and Wood Products - The preparation of melamine–formaldehyde (MF) resins for paper impregnation for wood panels laminating was found to be catalyzed by TiO2-mica...     

The influence of size and healing content on the performance of extrinsic self-healing coatings

Among the several approaches for the protection of metallic structures from corrosion, covering with a polymeric coating has attracted more attention due to their convenient application, cost-effective price, and the relatively benign environmental impact. However, the polymeric coatings are sensitive to mechanical/thermal shocks and aggressive environments, leading to damages in the coatings that affect their barrier performance. Self-healing polymeric coatings have introduced remarkable development by extending the service life and reducing maintenance costs, leading to a significant boost in the reliability and durability of the conventional polymeric coatings. Among the different strategies to develop self-polymeric coatings, encapsulating healing agent within micro/nanocapsules, micro/nanofibers, and microvascular systems and incorporating them within the conventional coatings have been widely acknowledged as the most applicable approach. However, several factors, such as the effect of the healing system's size and content, have a significant influence on healing performance. Therefore, this review aims to reveal the effects of healing system size and healing content on the self-healing performance in polymeric coatings through the analysis of recently published articles.