Cyberbullying Classification based on Social Network Analysis

With the popularity of social media platforms such as Facebook, Twitter, and Instagram, people widely share their opinions and comments over the Internet. Exten- sive use of social media has also caused a lot of problems. A representative problem is Cyberbullying, which is a serious social problem, mostly among teenagers. Cyber- bullying occurs when a social media user posts aggressive words or phrases to harass other users, and that leads to negatively affects on their mental and social well-being. Additionally, it may ruin the reputation of that media. We are considering the problem of detecting posts that are aggressive. Moreover, we try to detect Cyberbullies. In this research, we study Cyberbullying as a classification problem by combining text mining techniques, and the graph of the social network relationships based on a dataset from Twitter. We create an new dataset that has more information for each tweet (post). We improve the classification accuracy by considering the additional social network features based on the user’s follower list and retweet information

Multi-scale self-assembly of nanoenergetic materials utilizing functionalized graphene

The work described here-in focuses on the synthesis and characterization of novel nanoenergetic materials and is driven by overcoming the disadvantages of traditional nanoenergetic composites, improving the energetic performance as well as discovering the science boundary of nanoenergetic materials. Micro-scale and macro-scale structured energetic composites were synthesized via self-assembly process between Al nanoparticles, metal oxide nanoparticles and functionalized graphene. A novel gelation process of reduced graphene oxide was developed and utilized for self-assembling Al and Bi2O3 into macroscale structures with enhanced energetic performance and handling safety. The process successfully reduced graphene oxide sheets into rGO, forming a 3D structure with high porosity, controllable density, size, shape and chemical composition. The phase separation between Al and Bi2O3 was minimized, and the energetic reactivity of both nanoparticles was retained. Therefore, the final product rGO/Al/Bi2O3 exhibited 25% increase in energetic release during equilibrium reaction. A more than 100% increase in combustion rate was observed due to the unique self-confining structure. The conductive rGO scaffold offered the product a better safety for handling by increasing the ignition threshold to electrostatic discharge by 4 orders. Halogenated graphene was also adopted as the additive for self-assembly with Al and Bi2O3 nanoparticles for micro-scale energetic composites. A fluorine, oxygen co-functionalized graphene (FGO) was synthesized via a gas -- solid XeF2 -- GO reaction. The stability of this material upon storage time, temperature and dispersing was examined, confirming both stable and unstable fluorine groups contained in its structure. After mixing with Al and Bi2O3 nanoparticles, the FGO/Al/Bi2O3 showed a 60% enhancement in energy release and an all-solid-state reaction between Al and Bi2O3 as the fluorine significantly weakened the alumina shell protecting Al core. Iodinated reduced graphene oxide (I-rGO) was also prepared to fabricate microscale self-assembled I-rGO/Al/Bi2O3. The I-rGO was synthesized by graphene oxide paper and hydroiodic acid, containing both chemically bonded single iodine atoms and intercalated polyiodide clusters between graphene layers. The loss of iodine contents, especially polyiodide clusters, from the structure upon heating, solvent effect and exfoliation was examined. After self-assembly with Al and Bi2O3 nanoparticles, the released iodine weakened the alumina shell by forming Al-O-I bond on it, reducing the reaction temperature and enhancing the energy release significantly. The conductive I-rGO also increased the threshold to electrostatic discharge of final I-rGO/Al/Bi2O3 by 4 orders, ensuring the safety during handling the material in large quantity.Includes bibliographical reference

Directionality Effects and Exceptions in Learning Phonological Alternations

The present study explores learning vowel harmony with exceptions using the artificial language learning paradigm. Participants were exposed to a back/round vowel harmony pattern in which one affix (either prefix or suffix, depending on the condition) alternated between /me/ and /mo/ depending on the phonetic feature of the stem vowels. In Experiment 1, participants were able to learn the behaviors of both alternating and non-alternating affixes, but were more likely to generalize to novel affixes for non-alternating items than alternating items. In Experiment 2, participants were exposed to training data that contained non-alternating affixes in prefix position while alternating affixes were all suffixes, or vice versa. Participants were able to extend the non-alternating affixes to the novel direction, suggesting that participants inferred a non-directional harmony pattern. Overall, the patterns of alternating affixes are harder to learn than patterns of exceptions that do not alternate, which aligns with previous findings supporting a non-alternation bias. Our study raises the question of how biases towards exceptionality and directionality interact in phonological learning

Bacterial biofilms and biomineralisation on titanium

This study investigated bacterial interactions with titanium, and evaluated the use of Serratia biomineralisation to produce a hydroxyapatite (HA) coating on titanium. Adherence of Gram-positive Staphylococcus epidermidis and Streptococcus sanguinis and Gram-negative Serratia sp. NCIMB 40259 and Escherichia coli was compared on commercially pure titanium, Ti6Al4V alloy, pure aluminium and pure vanadium. Grain boundaries, grain orientation and alloy phase structure did not influence adhesion or early proliferation. Adherence of all four strains was equivalent on pure titanium and Ti6Al4V and inhibited on pure aluminium. Serratia biomineralisation was used to introduce a crystalline coating on Al$_2$O$_3$ grit blasted titanium discs and a porous titanium mesh. The porous coating consisted of micro-scale spheres composed of nano-scale calcium deficient HA. Embedded alumina particles and alkali treatment did not noticeably alter precipitation of Serratia HA, nor the structure of the coating in comparison with non-treated substrates. Coatings were retained after sintering at 800$^\circ$C in argon, although the original curved plate-like crystals changed to nano-scale β-tricalcium phosphate particles. A phosphorous-rich diffusion zone formed at the coating-titanium interface. This biomineralised coating may have applications for coatings of implants in non load-bearing sites, and other non-clinical applications where a high surface area is the major concern.EThOS - Electronic Theses Online ServiceGBUnited Kingdo