title: Ensembles of restricted Hoeffding trees

authors: Bifet, Albert

subjects: design

abstract: The success of simple methods for classification shows that is is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this article, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weigh them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons' learning rate using the ADWIN change detection method for data streams, and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption. We also show that our stacking method can improve the performance of a bagged ensemble.

text: Ensembles of restricted Hoeffding trees The success of simple methods for classification shows that is is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this article, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weigh them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons' learning rate using the ADWIN change detection method for data streams, and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption. We also show that our stacking method can improve the performance of a bagged ensemble.

year: 2012

title: Students’ perceptions of education for sustainable development in the accounting and business curriculum at a business school in New Zealand

authors: Sharma, Umesh Prasad

subjects: learning

abstract: Purpose – The purpose of this paper is to explore students’ perceptions and understandings of, and attitudes towards, education for sustainable development (ESD) at Delta Business School (DBS) in New Zealand [1]. The aim is to extend the limited literature on students’ perceptions of ESD within an accounting and business curriculum. 
Design/methodology/approach – To ascertain the students’ evaluations of their ESD, a survey was administered to 60 accounting and business students at DBS. The survey data were supplemented with interview evidence from 20 of the 60 students to obtain a deeper understanding of the students’ evaluations. 
Findings – A majority of the students perceive ESD as a “good thing.” Students were supportive of the sustainable business learning experience offered at DBS. The results suggest that students’ knowledge of sustainable business practices improved significantly from their studies. 
Practical implications – The paper should assist education providers to assess how students perceive ESD. This may help bring about changes to improve the teaching of sustainable development. Universities can be the main providers of ESD, but other educational providers such as the professional accounting bodies will also need to manage the development of ongoing education processes. Most students at DBS believe they are obtaining a good understanding of the concept of sustainability. 
Originality/value – There is a shortage of research concerning how students perceive sustainable development education. This paper contributes to the discussion of what to incorporate in sustainable education programmes, to help students properly understand sustainable development. We believe accounting and business education should develop graduates into broad-minded thinkers with a capacity for independent and critical thought. This will prepare them for future leadership roles.

text: Students’ perceptions of education for sustainable development in the accounting and business curriculum at a business school in New Zealand Purpose – The purpose of this paper is to explore students’ perceptions and understandings of, and attitudes towards, education for sustainable development (ESD) at Delta Business School (DBS) in New Zealand [1]. The aim is to extend the limited literature on students’ perceptions of ESD within an accounting and business curriculum. 
Design/methodology/approach – To ascertain the students’ evaluations of their ESD, a survey was administered to 60 accounting and business students at DBS. The survey data were supplemented with interview evidence from 20 of the 60 students to obtain a deeper understanding of the students’ evaluations. 
Findings – A majority of the students perceive ESD as a “good thing.” Students were supportive of the sustainable business learning experience offered at DBS. The results suggest that students’ knowledge of sustainable business practices improved significantly from their studies. 
Practical implications – The paper should assist education providers to assess how students perceive ESD. This may help bring about changes to improve the teaching of sustainable development. Universities can be the main providers of ESD, but other educational providers such as the professional accounting bodies will also need to manage the development of ongoing education processes. Most students at DBS believe they are obtaining a good understanding of the concept of sustainability. 
Originality/value – There is a shortage of research concerning how students perceive sustainable development education. This paper contributes to the discussion of what to incorporate in sustainable education programmes, to help students properly understand sustainable development. We believe accounting and business education should develop graduates into broad-minded thinkers with a capacity for independent and critical thought. This will prepare them for future leadership roles.

year: 2014

title: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013

authors: Hicks, Brendan J.

abstract: The aim of this survey was to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura). In the current study we present the findings from the seventh year of sampling (2013) in view of previous surveys using boat electrofishing in the Ohau Channel. 
We used the University of Waikato's 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 1,025 fish (20.3 kg) from 11 sites comprising 2,817 lineal m and 11,484 m² in area on 27 November 2013. Common bully were the most abundant fish species (57% of the catch) followed by common smelt (36% of the catch).
Goldfish had their highest biomasses in the lower channel, especially at site 10 near Lake Rotoiti (up to 7.25 g m⁻²). Catch per unit effort (CPUE) for common bullies exceeded smelt CPUE at all sites except site 1, reflecting their greater densities. CPUE for rainbow trout was variable between the sites, and greatest at site 3. 
The abundance of common bullies in 2013 reversed the apparent trend of reducing abundance since these surveys started in 2007. The cause of fluctuating bully abundance is not known, and was not accounted for by water clarity expressed as black disc distance (BDD) or water conductivity. Poor water clarity can reduce the efficiency of electrofishing, but BDD was greater in 2012 than in 2011 when common bully densities were lower. In 2013, the apparent decline in smelt abundance was also reversed, but the relatively inefficient sampling resulting from boat electrofishing for these two species should be considered. 
The increased goldfish biomass in 2011-2013 arose because of targeted fishing in the excavated side branch, which clearly offers good habitat for goldfish. Removal of goldfish in the previous years may have reduced the density in the excavated side channel (site 11) compared to previous years. In 2013, a shortfin eel was caught, following the first shortfin eel encountered in the Ohau Channel in 2012.

text: Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013 The aim of this survey was to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura). In the current study we present the findings from the seventh year of sampling (2013) in view of previous surveys using boat electrofishing in the Ohau Channel. 
We used the University of Waikato's 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 1,025 fish (20.3 kg) from 11 sites comprising 2,817 lineal m and 11,484 m² in area on 27 November 2013. Common bully were the most abundant fish species (57% of the catch) followed by common smelt (36% of the catch).
Goldfish had their highest biomasses in the lower channel, especially at site 10 near Lake Rotoiti (up to 7.25 g m⁻²). Catch per unit effort (CPUE) for common bullies exceeded smelt CPUE at all sites except site 1, reflecting their greater densities. CPUE for rainbow trout was variable between the sites, and greatest at site 3. 
The abundance of common bullies in 2013 reversed the apparent trend of reducing abundance since these surveys started in 2007. The cause of fluctuating bully abundance is not known, and was not accounted for by water clarity expressed as black disc distance (BDD) or water conductivity. Poor water clarity can reduce the efficiency of electrofishing, but BDD was greater in 2012 than in 2011 when common bully densities were lower. In 2013, the apparent decline in smelt abundance was also reversed, but the relatively inefficient sampling resulting from boat electrofishing for these two species should be considered. 
The increased goldfish biomass in 2011-2013 arose because of targeted fishing in the excavated side branch, which clearly offers good habitat for goldfish. Removal of goldfish in the previous years may have reduced the density in the excavated side channel (site 11) compared to previous years. In 2013, a shortfin eel was caught, following the first shortfin eel encountered in the Ohau Channel in 2012.

year: 2014