Topic Analysis of Tweets on the European Refugee Crisis Using Non-negative Matrix Factorization

The ongoing European Refugee Crisis has been one of the most popular trending topics on Twitter for the past 8 months. This paper applies topic modeling on bulks of tweets to discover the hidden patterns within these social media discussions. In particular, we perform topic analysis through solving Non-negative Matrix Factorization (NMF) as an Inexact Alternating Least Squares problem. We accelerate the computation using techniques including tweet sampling and augmented NMF, compare NMF results with different ranks and visualize the outputs through topic representation and frequency plots. We observe that supportive sentiments maintained a strong presence while negative sentiments such as safety concerns have emerged over time

Two-layer Thermally Driven Turbulence: Mechanisms for Interface Breakup

It is commonly accepted that the breakup criteria of drops or bubbles in turbulence is governed by surface tension and inertia. However, also {\it{buoyancy}} can play an important role at breakup. In order to better understand this role, here we numerically study Rayleigh-B\'enard convection for two immiscible fluid layers, in order to identify the effects of buoyancy on interface breakup. We explore the parameter space spanned by the Weber number $5\leq We \leq 5000$ (the ratio of inertia to surface tension) and the density ratio between the two fluids $0.001 \leq \Lambda \leq 1$, at fixed Rayleigh number $Ra=10^8$ and Prandtl number $Pr=1$. At low $We$, the interface undulates due to plumes. When $We$ is larger than a critical value, the interface eventually breaks up. Depending on $\Lambda$, two breakup types are observed: The first type occurs at small $\Lambda \ll 1$ (e.g. air-water systems) when local filament thicknesses exceed the Hinze length scale. The second, strikingly different, type occurs at large $\Lambda$ with roughly $0.5 < \Lambda \le 1$ (e.g. oil-water systems): The layers undergo a periodic overturning caused by buoyancy overwhelming surface tension. For both types the breakup criteria can be derived from force balance arguments and show good agreement with the numerical results.Comment: 13 pages, 7 figure

A new approach for KM-fuzzy partial metric spaces

summary:The main purpose of this paper is to give a new approach for partial metric spaces. We first provide the new concept of KM-fuzzy partial metric, as an extension of both the partial metric and KM-fuzzy metric. Then its relationship with the KM-fuzzy quasi-metric is established. In particularly, we construct a KM-fuzzy quasi-metric from a KM-fuzzy partial metric. Finally, after defining the notion of partial pseudo-metric systems, a one-to-one correspondence between partial pseudo-metric systems and KM-fuzzy partial pseudo-metrics is constructed. Furthermore, a fuzzifying topology $\tau_{P}$ on X deduced from KM-fuzzy partial metric is established and some properties of this fuzzifying topology are discussed

Security Assessment Taxonomy

Learning today has shifted from face-to-face curriculum to distance learning. Recent advances in distance learning bring major changes in education and educators take different roles in teaching courses. As technology offers a great potential for distance learning, many schools have been adopting this innovative approach. This paper explores a project undertaken by a large US university. We examine a security course that employs a distance learning environment and investigate how this environment affects learners and educators. Our findings indicate that distance learning is not considered a superior teaching method; on the contrary, in many cases, students reported on technical difficulties working with an on-line system. We conclude that further study and research of this method is warranted in order to determine the long-term benefits of using distance learning and to address its many challenges

Learner engagement with written corrective feedback in ESL and EFL contexts : a qualitative research synthesis using a perception-based framework

Although research on the efficacy of written corrective feedback has received considerable attention in recent years, there is a dearth of research on learner engagement with written corrective feedback. Understanding how language learners engage with written corrective feedback is high on the agenda of feedback research because it provides a broadened perspective that feedback uptake is only one form of engagement, and that engagement with written corrective feedback is influenced by myriad contextual and individual factors. To narrow the research gap, this qualitative research synthesis examines learner engagement with written corrective feedback in English writing contexts through the lens of ecological systems theory and a perception-based framework. Focusing on 14 articles, relevant information was extracted and synthesised following three iterative stages informed by grounded theory to identify common engagement patterns and clarify relationships between factors affecting how learners engage with written corrective feedback. The results reveal the dynamic, contextualised and individualised nature of learner engagement with written corrective feedback. Pedagogical implications for practitioners are discussed to address the lingering issues around learner engagement with written corrective feedback.Publisher PDFPeer reviewe

The impact of physical conditions on network connectivity in wireless sensor network

In Wireless Sensor Networks, end-to-end routing paths need to be established when nodes want to communicate with the desired destination. For nodes assumed to be static, many routing protocols such as Directed Diffusion have been proposed to meet this requirement efficiently. The performance of such routing protocols is relative to the given network connectivity. This paper addresses mobile sensor nodes taking into account the diversity of scattered node density and investigates how physical conditions impact on network connectivity which in turn influences routing performance. Three analysis metrics: path availability, path duration, and interavailable path time are proposed to quantify the impact of different physical conditions on network connectivity. Simulation results show that the network connectivity varies significantly as a function of different physical conditions

HWN* Mobility Management Considering QoS, Optimisation and Cross Layer Issues

In this paper, we address mobility management for 4th generation heterogeneous networks from a quality of service (QoS), optimisation and cross layer design perspective. Users are classified as high profile, normal profile and low profile according to their differentiated service requirements. Congestion avoidance control and adaptive handover mechanisms are implemented for efficient cooperation within the mobile heterogeneous network environment consisting of a TDMA network, ad hoc network and relay nodes. A previous proposed routing algorithm is also revised to include mobility management

Resource Sharing via Planed Relay for HWN

We present an improved version of adaptive distributed cross-layer routing algorithm (ADCR) for hybrid wireless network with dedicated relay stations () in this paper. A mobile terminal (MT) may borrow radio resources that are available thousands mile away via secure multihop RNs, where RNs are placed at pre-engineered locations in the network. In rural places such as mountain areas, an MT may also communicate with the core network, when intermediate MTs act as relay node with mobility. To address cross-layer network layers routing issues, the cascaded ADCR establishes routing paths across MTs, RNs, and cellular base stations (BSs) and provides appropriate quality of service (QoS). We verify the routing performance benefits of over other networks by intensive simulation