Prediction interval-based modelling of polymerization reactor: a new modelling strategy for chemical reactors

Precise and reliable modelling of polymerization reactor is challenging due to its complex reaction mechanism and non-linear nature. Researchers often make several assumptions when deriving theories and developing models for polymerization reactor. Therefore, traditional available models suffer from high prediction error. In contrast, data-driven modelling techniques provide a powerful framework to describe the dynamic behaviour of polymerization reactor. However, the traditional NN prediction performance is significantly dropped in the presence of polymerization process disturbances. Besides, uncertainty effects caused by disturbances present in reactor operation can be properly quantified through construction of prediction intervals (PIs) for model outputs. In this study, we propose and apply a PI-based neural network (PI-NN) model for the free radical polymerization system. This strategy avoids assumptions made in traditional modelling techniques for polymerization reactor system. Lower upper bound estimation (LUBE) method is used to develop PI-NN model for uncertainty quantification. To further improve the quality of model, a new method is proposed for aggregation of upper and lower bounds of PIs obtained from individual PI-NN models. Simulation results reveal that combined PI-NN performance is superior to those individual PI-NN models in terms of PI quality. Besides, constructed PIs are able to properly quantify effects of uncertainties in reactor operation, where these can be later used as part of the control process. © 2014 Taiwan Institute of Chemical Engineers.

Air Asia: what has made it Asia's largest budget airline?

The success of Asia’s largest budget airline, Air Asia is analysed in this paper with a view to gain an insight into the factors that have contributed towards it. Air Asia’s management has concentrated on costs efficiencies, attention to controllable variables that reduce total risk and replication of the multi-hub model that generates operational efficiencies along with the creation of a regional identity that has gone a long way in making this airline what it is.

Managing ICT costs in e-commerce organizations with the time-driven activity-based costing model: a note

As online business activities continue to grow, it is important for organizations to understand the implications of being an e-commerce organization and the appropriateness of applying existing business techniques to e-commerce organizations. This paper examines issues in managing information and communication technologies (ICT) costs in e-commerce organizations and the potentials of the Time-Driven Activity-Based Costing (TDABC) model as a solution to these issues. The reliance on ICT in value creation, the unique natures of ICT costs and the need to maintain updated costing models present new challenges to e-commerce organizations in management of ICT costs. The TDABC model, as a variant of the Activity-Based Costing (ABC) model, inherits the strengths of activity-based paradigm and has unique features that can provide additional benefits to e-commerce organizations.

Board structure and firm performance : evidence from an emerging economy

We investigate the relationship between corporate board structure and firm performance of Bangladeshi companies. Using a sample of 654 firm- year observations for the period 2005-2009, the results show some support for aspects of agency theory as a greater proportion of independent directors on boards is related to better firm performance. Supporting resource dependence theory our result also suggest that larger boards provide valuable business experience, expertise, skill and social and professional networks which might add substantial business resources to the firms and thus positively impact on performance. We also find that female and foreign directors in Bangladesh provide more monitoring which leads to better firm performance. Our study contributes to extant research on board structure–performance relationship by providing evidence from an emerging economy context which is characterised by ownership concentration, family dominance and poor regulatory oversight.

Forensic identification of students outsourcing assignment projects from freelancer.com

This paper reports the increasing popularity of outsourcing academic works by university students motivated by the lure of lucrative dividends and visa opportunities. Due to a lack of formal methods in detecting such transactions, freelance websites are thriving in facilitating the trade of outsourced assignments. This is compounded by the fact that many university staff have neither the time nor training to perform complex media analysis and forensic investigations. This paper proposes a method to aid in the identification of those who outsource assignment works on the most popular site freelancer.com. We include a recent real-world case study to demonstrate the relevancy and applicability of our methodology. In this case study, a suspect attempts to evade detection via use of anti-forensics which demonstrates the capability and awareness of evasion techniques used by students.

Equity market price interactions between China and the other markets within the Chinese states equity markets

This study examines the cointegrating and long-term causal relationships of equity market prices in equity markets of Chinese states namely, Shanghai, Shenzhen, Hong Kong, Taiwan and Singapore. I cover the period between October 5, 1992 and March 20, 2006, taking into account both the Asian financial crisis and the opening-up of China’s equity markets in recent years. First, I analysis the cointegration by utilizing Johansen’s (1988) cointegration tests. I find that a long-term equilibrium relationship measured by cointegration has been established among Shanghai, Shenzhen, Hong Kong and Taiwanese markets and, to a lesser degree, between these markets and the Singapore market since 1998. Secondly, this study examines causality by exploring the bootstrapped Toda-Yamamoto non-causality tests. I find that there is strong evidence of a bi-directional causality between Shanghai and Shenzhen markets after 1998. Furthermore, I also find that there are more causal linkages between the Chinese states equity markets: two mainland Chinese markets, Hong Kong, Taiwan, and Singapore became more dependent on each other. The robustness of the above findings is confirmed by the use of a bootstrap test employed to test the validity of my results.

The Christmas effect-special dividend announcements

This paper examines the Halloween effect in special dividend announcements. We find that firms are more likely to announce special dividends at the end of a year, especially in the months of November and December. There is a Halloween effect in the announcements, but more importantly, there is a Christmas effect in the propensity and abnormal returns of special dividends. This paper provides initial evidence on the Christmas effect of special dividend payments. It links monthly effects in stock returns and corporate events to explain the likelihood of the occurrence of special dividend announcements. The results of this paper shed light on why corporate events are more likely to occur in some periods, but less likely to occur in others.

Does political economy reduce agency costs? Some evidence from dividend policies around the world

This study shows that firms in proportional-electoral countries pay out lower dividends and that the correlation between a firm's growth potential and dividend payout ratio is weaker in proportional-electoral countries. However, firms in proportional-electoral countries that cross-list in majoritarian system countries, tend to pay out higher dividends and the negative relation between growth potential and dividend payout tend to be stronger than their peers that do not cross-list. For a few countries that changed their electoral system towards a more proportional system, we observe a decrease in dividend payout ratio and a weaker relation between growth and dividends after the change. Overall these results indicate that a country's political system affects the severity of agency problems. Further, the effect of legal origin on dividend policy reverses once we include the political economy variables in the regressions. We also document that the electoral system not only affects the amount of dividends paid by a firm but also the form of payment.

Expert teachers’ discursive moves in science classroom interactive talk

It is well established that teacher-student interactive talk is critically important in supporting students to reason and learn in science. Teachers’ discursive moves in responding to student input are keys to developing and supporting a rich vein of interactive discussion. While initiation-response-evaluation (IRE) sequences have been shown to dominate science classroom discourse patterns worldwide, teacher ‘prompts’ are important for opening up opportunities for reasoning and higher level learning. This paper describes the analysis of video sequences for five expert elementary teachers across three countries to develop a coding scheme for these teachers’ ‘discursive moves’ to guide and respond to student inputs, that unpacks more completely the strategies they use to develop interactive discussion. The analysis showed varied patterns of knowledge transaction, with teacher discursive moves serving three broad purposes: to elicit and acknowledge student responses, to clarify and to extend student ideas. The patterns of talk were also related to the dialogic-authoritative distinction in analysis of talk, to show that this distinction is only clear for particular types of expert practice. While the particular moves teachers use vary across parts of lessons we argue that they are revealing of teachers’ particular beliefs and of systemic constraints, and that there exist patterns in the use of the discursive categories that capture how expert teachers build deeper level knowledge in classroom interactive talk. We describe ways in which the analysis can inform science teacher education and the professional learning of teachers of science.

Community-school collaborations in science: towards improved outcomes through better understanding of boundary issues

There is growing interest, worldwide, in collaboration between schools and community organisations in contributing to and enriching school science programs, yet such collaborations are inadequately understood. This paper reports data from an Australian study designed to probe the views of members of the community who have participated in a broad range of such collaborations in school science programmes in order to better understand the issues which impact on their operation. The data were collected by interviews with the community participants selected by opportunistic sampling. The analysis reveals a number of issues—purposes, communication, organisational structures and curriculum—which can be seen as impacting on the collaborations. These are examined through the concepts of communities of practice, boundaries and boundary crossing, associated with people from scientific communities of practice interacting with school communities. The paper reflects on the implications of these findings for constructing effective school-community collaboration in school science programs.