Segue: Overviewing Evolution Patterns of Egocentric Networks by Interactive Construction of Spatial Layouts

Getting the overall picture of how a large number of ego-networks evolve is a common yet challenging task. Existing techniques often require analysts to inspect the evolution patterns of ego-networks one after another. In this study, we explore an approach that allows analysts to interactively create spatial layouts in which each dot is a dynamic ego-network. These spatial layouts provide overviews of the evolution patterns of ego-networks, thereby revealing different global patterns such as trends, clusters and outliers in evolution patterns. To let analysts interactively construct interpretable spatial layouts, we propose a data transformation pipeline, with which analysts can adjust the spatial layouts and convert dynamic egonetworks into event sequences to aid interpretations of the spatial positions. Based on this transformation pipeline, we developed Segue, a visual analysis system that supports thorough exploration of the evolution patterns of ego-networks. Through two usage scenarios, we demonstrate how analysts can gain insights into the overall evolution patterns of a large collection of ego-networks by interactively creating different spatial layouts.Comment: Published at IEEE Conference on Visual Analytics Science and Technology (IEEE VAST 2018

THE FATE OF DISCHARGED POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) IN WATER STREAMS

Polycyclic aromatic hydrocarbons (PAHs), also known as polynuclear aromatic hydrocarbons, are potent atmospheric pollutants consisting of fused aromatic rings and do not carry or contain heteroatoms/substituents. 16 of PAHs have been classified by Environmental Protection Agency (EPA) for possible carcinogenic properties. It is discovered that PAHs are found abundant in water stream. Most of the PAHs are discharged without getting treated properly at sewage treatment plant. When exposed to the environment, the PAHs will be degraded either in microbial degradation or photo degradation pathway. The PAHs will be then transformed to various metabolites, creating ‘daughters’ and byproducts along its degradation. They may also be mutagenic or carcinogenic even if their parent compounds are not (International Association of Oil and Gas Producers, 2005). A research study was conducted on former works on PAHs and its metabolites. This included the current study to identify various sources of PAHs in water stream in river of Sungai Perak near the area Teluk Kepayang. Samples were obtained from influent of water treatment plant (WTP) in Teluk Kepayang and were analysed with Gas Chromatography/Mass Spectrometry (GC/MS) to formulate conversion path of carcinogenic PAHs. Tests were performed as well on influent and effluent of Universiti Teknologi PETRONAS (UTP) sewage treatment plant (STP) for studies on sewage polluted urban streams. The samples were then used as test solution for guppy (Poecilia reticulate) as their living environment to establish toxicity intensity of carcinogenic PAHs parents and daughter products through 96hours acute toxicity test. GC/MS analysis identified phthalic acid and benzoic acid as major derivatives found in all samples. The analysis showed the detection of Naphthalene and few other suspected derivatives in influent WTP Teluk Kepayang sample. Mortality rate of Poecilia reticulate against time exposure of 96 hours was 20% for influent Teluk Kepayang WTP and 10% for influent UTP STP whereas the rate is 0% for effluent UTP STP. It was observed that the amount of PAHs and its derivatives detected in both effluent and influent of UTP STP and influent of Teluk Kepayang WTP are not harmful to the environment

Modelling wall-flow diesel particulate filter regeneration processes

This research was aimed at providing a better understanding of regeneration processes in wall-flow diesel particulate filters (DPFs), with emphasis on the combustion of particulate matter (PM). A 1-D model was used to investigate the effects of inherent PM properties on DPF regeneration behaviour. These properties were mean particulate diameter, porosity and bulk density of the PM, as well as the kinetic parameters of PM oxidation, i.e. frequency factor and activation energy. A parametric study showed that the activation energy of the PM oxidation reaction was the most important parameter and this was followed by the associated frequency factor, bulk density and porosity and mean particulate diameter. Due to the importance of the kinetic parameters of the PM oxidation reactions, a new 1-D model with a multi-step reaction scheme that required no tuneable kinetic parameters for the PM oxidation reactions was developed. [Continues.

Simulation of a Bioreactor with an Improved Fermentation Kinetics – Fluid Flow Model

Ethanolic fermentation experiments were carried out using a stirred tank equipped with a Rushton turbine. The data were used to estimate kinetic parameters based on a newly developed kinetics model originated from Herbert’s microbial kinetics model. This newly developed model took into account the effects of aeration rate (AR) and stirrer speed (SS). Experiment data i.e. glucose, ethanol and biomass concentrations obtained from different experiment sets were used for kinetics prediction. Assuming a perfectly-stirred condition, the kinetic parameters were initially estimated through solving Herbert’s model equations. These estimated kinetic parameters were then incorporated in a Computational Fluid Dynamics (CFD) model but the simulation results did not agree well with the experiment findings. Based on the proposed CFD model, the kinetic parameters were corrected. The correction factors were expressed as functions of AR and SS. This analysis highlighted the need to estimate kinetic parameters based on CFD simulation because it is able to account for the spatial variation in a reactor. A sensitivity analysis of the kinetic parameters using the coupled CFD-fermentation kinetic model was carried out to further understand the influence of each set of kinetic parameters on the model prediction. It was found that the sensitivities of the kinetic parameters varied with the concentrations of glucose, ethanol and biomass

Nonlinear Hall Effects in Strained Twisted Bilayer WSe2_2

Recently, it has been pointed out that the twisting of bilayer WSe$_2$ would generate topologically non-trivial flat bands near the Fermi energy. In this work, we show that twisted bilayer WSe$_2$ (tWSe$_2$) with uniaxial strain exhibits a large nonlinear Hall (NLH) response due to the non-trivial Berry curvatures of the flat bands. Moreover, the NLH effect is greatly enhanced near the topological phase transition point which can be tuned by a vertical displacement field. Importantly, the nonlinear Hall signal changes sign across the topological phase transition point and provides a way to identify the topological phase transition and probe the topological properties of the flat bands. The strong enhancement and high tunability of the NLH effect near the topological phase transition point renders tWSe$_2$ and related moire materials new platforms for rectification and second harmonic generations.Comment: 5 pages, 3 figures. Comments are welcom

Orbital Fulde-Ferrell pairing state in moir\'e Ising superconductors

In this work, we study superconducting moir\'e homobilayer transition metal dichalcogenides where the Ising spin-orbit coupling (SOC) is much larger than the moir\'e bandwidth. We call such noncentrosymmetric superconductors, moir\'e Ising superconductors. Due to the large Ising SOC, the depairing effect caused by the Zeeman field is negligible and the in-plane upper critical field ($B_{c2}$) is determined by the orbital effects. This allows us to study the effect of large orbital fields. Interestingly, when the applied in-plane field is larger than the conventional orbital $B_{c2}$, a finite-momentum pairing phase would appear which we call the orbital Fulde-Ferrell (FF) state. In this state, the Cooper pairs acquire a net momentum of $2q_B$ where $2q_B=eBd$ is the momentum shift caused by the magnetic field $B$ and $d$ denotes the layer separation. This orbital field-driven FF state is different from the conventional FF state driven by Zeeman effects in Rashba superconductors. Remarkably, we predict that the FF pairing would result in a giant superconducting diode effect under electric gating when layer asymmetry is induced. An upturn of the $B_{c2}$ as the temperature is lowered, coupled with the giant superconducting diode effect, would allow the detection of the orbital FF state.Comment: 6 pages, 4 figures, plus Supplementary Materia