title: Building ensembles of adaptive nested dichotomies with random-pair selection

authors: Leathart, Tim

subjects: computer science

abstract: A system of nested dichotomies is a method of decomposing a multi-class problem into a collection of binary problems. Such a system recursively applies binary splits to divide the set of classes into two subsets, and trains a binary classifier for each split. Although ensembles of nested dichotomies with random structure have been shown to perform well in practice, using a more sophisticated class subset selection method can be used to improve classification accuracy. We investigate an approach to this problem called random-pair selection, and evaluate its effectiveness compared to other published methods of subset selection. We show that our method outperforms other methods in many cases when forming ensembles of nested dichotomies, and is at least on par in all other cases. The software related to this paper is available at https://svn.cms.waikato.ac.nz/svn/weka/trunk/packages/ internal/ensemblesOfNestedDichotomies/.

text: Building ensembles of adaptive nested dichotomies with random-pair selection A system of nested dichotomies is a method of decomposing a multi-class problem into a collection of binary problems. Such a system recursively applies binary splits to divide the set of classes into two subsets, and trains a binary classifier for each split. Although ensembles of nested dichotomies with random structure have been shown to perform well in practice, using a more sophisticated class subset selection method can be used to improve classification accuracy. We investigate an approach to this problem called random-pair selection, and evaluate its effectiveness compared to other published methods of subset selection. We show that our method outperforms other methods in many cases when forming ensembles of nested dichotomies, and is at least on par in all other cases. The software related to this paper is available at https://svn.cms.waikato.ac.nz/svn/weka/trunk/packages/ internal/ensemblesOfNestedDichotomies/.

year: 2016

title: Hotspots: Modelling capacity for vector-borne disease risk analysis in New Zealand: A case study of Ochlerotatus camptorhynchus incursions in New Zealand

authors: de Wet, Neil

subjects: New Zealand

abstract: This Hotspots case study of Oc. camptorhynchus in New Zealand forms part of the wider aims and
objectives of the Hotspots project. The overall aims of the case study were:
1. To evaluate the performance of the Hotspots model as a risk analysis tool for Oc.
camptorhynchus;
2. To use and learn from the experience of the various incursions of Oc. camptorhynchus in
order to critically assess and improve the model;
3. To gain experience in using the model for risk analysis for Oc. camptorhynchus in
particular, and in so doing, also develop experience applicable to risk analysis for other
vectors of concern (Table 1); and,
4. To develop an experience and knowledge base as well as guidelines for future use of the
model in its various applications related to biosecurity, surveillance and risk assessment
and management.

text: Hotspots: Modelling capacity for vector-borne disease risk analysis in New Zealand: A case study of Ochlerotatus camptorhynchus incursions in New Zealand This Hotspots case study of Oc. camptorhynchus in New Zealand forms part of the wider aims and
objectives of the Hotspots project. The overall aims of the case study were:
1. To evaluate the performance of the Hotspots model as a risk analysis tool for Oc.
camptorhynchus;
2. To use and learn from the experience of the various incursions of Oc. camptorhynchus in
order to critically assess and improve the model;
3. To gain experience in using the model for risk analysis for Oc. camptorhynchus in
particular, and in so doing, also develop experience applicable to risk analysis for other
vectors of concern (Table 1); and,
4. To develop an experience and knowledge base as well as guidelines for future use of the
model in its various applications related to biosecurity, surveillance and risk assessment
and management.

year: 2005-04

title: The influence of harvest frequency and regime on the performance of  Filamentous Algae Nutrient Scrubbers treating agricultural drainage

authors: Waaka, Okeroa

subjects: Filamentous algae nutrient scrubbers

abstract: Filamentous algae nutrient scrubbers (FANS) are ecologically engineered flow-ways that have recently been proposed as a potential on-farm method to treat agricultural drainage in New Zealand. The effectiveness of FANS systems to remove nutrients from polluted waters and to produce algal biomass as a harvestable by-product is heavily influenced by operational parameters. As filamentous algae grow on a flow-way, the thickness of the algal biomass increases and begins to reduce light penetration and nutrient assimilation. Therefore, periodic harvesting of the accumulated algal biomass plays a key role in determining the biomass production and nutrient removal performance of FANS systems. 

The overall aim of this study was to investigate the influence of harvest frequency and harvest regime on biomass productivity and nutrient removal of an outdoor FANS system. The FANS system used in this study consisted of six flow-ways that were split into two sets of triplicate flow-ways named “FULL” and “PARTIAL”. Harvesting of the FULL replicate flow-ways occurred once a week, where algal biomass accumulated along the entirety of the flow-way was collected. Harvesting of the PARTIAL replicate flow-ways occurred twice a week, where the algal biomass was collected in alternate meter sections (a total of 3-metre harvest length every 3 – 3.5 days). 

The increased harvest frequency (3 – 3.5 days) and sectioned harvest regime implemented in the PARTIAL replicate flow-ways significantly improved biomass productivity (3.2 g DW m-2. d) in comparison to the less frequent (7 – 7.5 days) and total harvest regime implemented in the FULL replicate flow-ways (0.9 g DW m-2. d). However, there was no significant difference in nutrient removal rates between the PARTIAL and FULL replicate flow-ways. There is still limited understanding of how operational parameters can be optimized to maximise biomass productivity and nutrient removal in FANS systems on a year-round basis. However, the findings of this study demonstrate that an increased harvest frequency and sectioned harvest regime can improve the biomass yield of filamentous algae grown on an outdoor FANS system during spring to summer months. 

Furthermore, this study has suggested the potential for Māori acceptance of FANS technology and algal biomass use. In person interviews with whanau and iwi members recalled use of algal biomass harvested from rivers and streams as fertilizer for vegetable gardens or bait for eel trapping. Moreover, the literature review and in person interviews highlighted the importance of identifying and using ngā kupu (words and terms) used by Māori to describe freshwater algae. The intergenerational observation and utilization of algae as a resource by Māori may reveal an awareness of biological processes that either differs or compliments a Western Science point of view. Incorporating this knowledge into current water and environmental management practices could be extremely beneficial for improving water quality of streams in Aotearoa New Zealand.

text: The influence of harvest frequency and regime on the performance of  Filamentous Algae Nutrient Scrubbers treating agricultural drainage Filamentous algae nutrient scrubbers (FANS) are ecologically engineered flow-ways that have recently been proposed as a potential on-farm method to treat agricultural drainage in New Zealand. The effectiveness of FANS systems to remove nutrients from polluted waters and to produce algal biomass as a harvestable by-product is heavily influenced by operational parameters. As filamentous algae grow on a flow-way, the thickness of the algal biomass increases and begins to reduce light penetration and nutrient assimilation. Therefore, periodic harvesting of the accumulated algal biomass plays a key role in determining the biomass production and nutrient removal performance of FANS systems. 

The overall aim of this study was to investigate the influence of harvest frequency and harvest regime on biomass productivity and nutrient removal of an outdoor FANS system. The FANS system used in this study consisted of six flow-ways that were split into two sets of triplicate flow-ways named “FULL” and “PARTIAL”. Harvesting of the FULL replicate flow-ways occurred once a week, where algal biomass accumulated along the entirety of the flow-way was collected. Harvesting of the PARTIAL replicate flow-ways occurred twice a week, where the algal biomass was collected in alternate meter sections (a total of 3-metre harvest length every 3 – 3.5 days). 

The increased harvest frequency (3 – 3.5 days) and sectioned harvest regime implemented in the PARTIAL replicate flow-ways significantly improved biomass productivity (3.2 g DW m-2. d) in comparison to the less frequent (7 – 7.5 days) and total harvest regime implemented in the FULL replicate flow-ways (0.9 g DW m-2. d). However, there was no significant difference in nutrient removal rates between the PARTIAL and FULL replicate flow-ways. There is still limited understanding of how operational parameters can be optimized to maximise biomass productivity and nutrient removal in FANS systems on a year-round basis. However, the findings of this study demonstrate that an increased harvest frequency and sectioned harvest regime can improve the biomass yield of filamentous algae grown on an outdoor FANS system during spring to summer months. 

Furthermore, this study has suggested the potential for Māori acceptance of FANS technology and algal biomass use. In person interviews with whanau and iwi members recalled use of algal biomass harvested from rivers and streams as fertilizer for vegetable gardens or bait for eel trapping. Moreover, the literature review and in person interviews highlighted the importance of identifying and using ngā kupu (words and terms) used by Māori to describe freshwater algae. The intergenerational observation and utilization of algae as a resource by Māori may reveal an awareness of biological processes that either differs or compliments a Western Science point of view. Incorporating this knowledge into current water and environmental management practices could be extremely beneficial for improving water quality of streams in Aotearoa New Zealand.

year: 2023