Using Social Network Analysis to Visualize the Social-Media Networks of Community Groups: Two Case Studies from Sydney

Community participation in planning is generally considered crucial for the delivery of positive outcomes; however, the network structures that can be created by community groups that use social media and participate in the network are not widely understood. This paper explores the use of social media, specifically Twitter, by two community groups in Sydney. In the context of this study, community groups are self-created and organized groups of citizens that form to oppose a proposal to amend planning controls for a specific site. Employing the research technique of Social Network Analysis (SNA), this paper seeks to visualize community group social media networks, as well as understand who is connected and who is participating within the networks. For the two community groups investigated, it was found that they do not attract large numbers of friends and followers on Twitter and key stakeholders play a passive listening role in the networks.     

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

Abstract

In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction.     

Classification into homogeneous groups using combined cluster and discriminant analysis

The classification of observations into groups is a general procedure in modern research. However, when searching for homogeneous groups the difficulty of deciding whether further division of a classification is necessary or not to obtain the desired homogeneous groups arises. The presented method, Combined cluster and discriminant analysis (CCDA), aims to facilitate this decision.CCDA consists of three main steps: (I) a basic grouping procedure; (II) a core cycle where the goodness of preconceived and random classifications is determined; and (III) an evaluation step where a decision has to be made regarding division into sub-groups. These steps of the proposed method were implemented in R in a package, under the name of ccda.To present the applicability of the method, a case study on the water quality samples of Neusiedler See is presented, in which CCDA classified the 33 original sampling locations into 17 homogeneous groups, which could provide a starting point for a later recalibration of the lake's monitoring network.     

Fixed-order loop shaping robust controller design for parametric models to damp inter-area oscillations

The inter-area oscillations are common in power systems and can occur due to the changes in the load or generating power especially in long transmission lines. This paper presents the design of a robust fixed-order loop shaping controller to damp out the inter-area oscillations and to enhance the stability of the power system. The proposed loop shaping method is based on the shaping of the open-loop transfer function in the Nyquist diagram through minimizing the quadratic error between the actual and the desired open loop transfer functions in the frequency domain. The proposed method is robust with respect to multi-model uncertainty. Despite other robust controller design methods, the proposed approach deals with the entire system i.e. there is no need to reduce the system and still leads to a lower order controller. In addition, most of the robust methods are heavily dependent on selecting some weight filters which is not required in the proposed approach. This method is applied to the two-area four-machine system and 68 bus system and the effectiveness and robustness of the proposed method in damping inter-area oscillations are validated using case studies.     

The role of tutors in peer led teaching

Problem based learning can impact not only on students’ academic performance but also their social interactions within their peer group, and many institutions have embedded such teaching within their core curriculum. This paper looks at the interactions within a first year undergraduate engineering cohort that uses peers to tutor small groups through problem based learning at a Scottish Higher Education Institution. Most significantly, this work focusses on the impact that these interactions have on the students engaged as tutors within the programme, bridging the gap left by previous studies and providing an insight into how tutors are affected by their experiences. It was found that the recruitment of tutors requires careful consideration of their social as well as academic qualities, and that they should receive training and guidance within their adopted roles that takes account of social factors, questioning the traditional practice of employing individuals purely on the basis that they have studied the class previously themselves. The dynamic of tutor position with regard to the presence of senior staff is also explored, and suggests mechanisms for further student development.     

A partial binary tree DEA-DA cyclic classification model for decision makers in complex multi-attribute large-group interval-valued intuitionistic fuzzy decision-making problems

This paper proposes the idea of combining “interest groups” with the practical decision information to classify the decision makers (DMs) in complex multi-attribute large-group decision-making (CMALGDM) problems in interval-valued intuitionistic fuzzy (IVIF) environment. It constructs a partial binary tree DEA-DA cyclic classification model to achieve the multiple groups’ classification of DMs. Not only does this method provide references for the classification of DMs when the decision information is known, but it also lays foundations for DMs’ effective weight determination and the aggregation of decision information. First, this paper normalizes all of the cost attributes into benefit attributes to avoid the wrong decision result. Second, it employs the C-OWA operator to transform IVIF number (IVIFN) samples into single-valued samples. With respect to this transformation, this paper provides the corresponding BUM functions of DMs according to their risk attitudes; therefore, the preference information of DMs can be more objectively aggregated. Third, this paper adopts the partial binary tree DEA-DA cyclic classification model to present an accurate classification of DMs. Thus, for each interest group, group members with different interest preferences can be distinguished and distributed to the appropriate groups. Finally, to show the feasibility and validity of the model, we give an illustrative example.     

Influence of support’s oxygen functionalization on the activity of Pt/carbon xerogels catalysts for methanol electro-oxidation

Highly mesoporous carbon xerogels (CXs) were synthesized using two different resorcinol to catalyst, R/C, molar ratios and functionalized with different oxidation treatments. The synthesized carbon materials were used as supports for Pt particles, deposited by impregnation and reduction in formic acid. Both carbon supports and the catalysts prepared were characterized by means of N₂ physisorption, scanning and transmission electron microscopy, temperature programmed desorption and X-ray diffraction. The electrochemical activity of the catalysts towards the oxidation of carbon monoxide and methanol was assayed by means of cyclic voltammetry and chronoamperometry. Textural characterization of the materials prepared evidenced more developed and mesopore-enriched porous structure for the carbon xerogel prepared using the highest R/C molar ratio. Enhanced textural properties of this material led to the preparation of highly active Pt-catalysts, which showed increased tolerance to CO and higher activity in methanol electro-oxidation, in comparison to Pt-E-TEK and the catalysts prepared in an analogous way using Vulcan XC-72R carbon black as support. Functionalization treatments resulted in enhanced dispersion, lower Pt crystal size and improved catalytic performance in the case of the catalysts prepared using the carbon xerogel possessing a less developed porous structure. Pt agglomeration was found to strongly determine the activity of the catalysts prepared. At high potentials, i.e. 1 V vs. RHE, the catalyst prepared using the carbon xerogel submitted to the most stringent oxidation treatment showed the highest specific peak activity towards methanol electro-oxidation, probably due to the positive influence of the presence of oxygen surface groups in Pt-carbon interaction, in spite of the higher agglomeration extent confirmed by TEM. On the other hand, at 0.60 V vs. RHE, highest activity towards methanol electro-oxidation was determined for the catalysts prepared using the non-functionalized carbon xerogel which can be explained in terms of enhanced reactant/product diffusion together with intrinsic higher catalytic activity due to lower Pt crystal size. In any case, the activity of this catalyst prepared using a carbon xerogel as support was found to be more than 2 times higher than the one determined for Pt/E-TEK, confirming the considerable improvement of the electrocatalytic system by means of optimization of the carbon support employed.     

Can Our Group Survive? An Investigation of the Evolution of Mixed‐Mode Groups

Applying an ecological and evolutionary perspective, this study examines the evolution and the sustainability of “mixed‐mode groups,” a type of voluntary association created and organized online to interact physically in geographically defined ways. Meetup.com is a website that facilitates the creation and coordination of mixed‐mode groups. Analysis of interviews with 34 Meetup group organizers and a longitudinal analysis of 100 randomly selected Meetup groups revealed the evolutionary processes at the group and population level, respectively. Specifically, the ecological factor of population density, the demographic factor of group age, the group's profit orientation, experience of leadership change and shared leadership, and external ties played decisive roles in predicting group survival. Implications of the findings for theoretical and practical contributions are discussed.     

On extensions of subshifts by finite groups

λ-Graph systems are labelled Bratteli diagrams with shift operations. They present subshifts. Their matrix presentations are called symbolic matrix systems. We define skew products of λ-graph systems and study extensions of subshifts by finite groups. We prove that two canonical symbolic matrix systems are G-strong shift equivalent if and only if their presented subshifts are G-conjugate.     

Multi objective load frequency control using hybrid bacterial foraging and particle swarm optimized PI controller

Excessive load demand with reliability in power availability, demands for interconnection of large number of generating units over existing tie lines. Due to sudden change in demand, the power transfer over existing tie lines working close to their thermal limits results in low frequency power oscillations. Thus, in modern power systems the study of mitigation of these frequency oscillations is more involved and formulates the area of Load Frequency Control (LFC). Many conventional and heuristic control techniques have been recently applied to address the issue of LFC. This paper investigates load frequency control of large interconnected power system consisting of conventional and renewable energy sources, using hybrid heuristic approach. The proposed strategy is shown to result in improved system damping resulting in faster mitigation of low frequency oscillations.