title: One-Class Classification by Combining Density and Class Probability Estimation

authors: Hempstalk, Kathryn

subjects: computer science

abstract: One-class classification has important applications such as outlier and novelty detection. It is commonly tackled using density estimation techniques or by adapting a standard classification algorithm to the problem of carving out a decision boundary that describes the location of the target data. In this paper we investigate a simple method for one-class classification that combines the application of a density estimator, used to form a reference distribution, with the induction of a standard model for class probability estimation. In this method, the reference distribution is used to generate artificial data that is employed to form a second, artificial class. In conjunction with the target class, this artificial class is the basis for a standard two-class learning problem. We explain how the density function of the reference distribution can be combined with the class probability estimates obtained in this way to form an adjusted estimate of the density function of the target class. Using UCI datasets, and data from a typist recognition problem, we show that the combined model, consisting of both a density estimator and a class probability estimator, can improve on using either component technique alone when used for one-class classification. We also compare the method to one-class classification using support vector machines.

text: One-Class Classification by Combining Density and Class Probability Estimation One-class classification has important applications such as outlier and novelty detection. It is commonly tackled using density estimation techniques or by adapting a standard classification algorithm to the problem of carving out a decision boundary that describes the location of the target data. In this paper we investigate a simple method for one-class classification that combines the application of a density estimator, used to form a reference distribution, with the induction of a standard model for class probability estimation. In this method, the reference distribution is used to generate artificial data that is employed to form a second, artificial class. In conjunction with the target class, this artificial class is the basis for a standard two-class learning problem. We explain how the density function of the reference distribution can be combined with the class probability estimates obtained in this way to form an adjusted estimate of the density function of the target class. Using UCI datasets, and data from a typist recognition problem, we show that the combined model, consisting of both a density estimator and a class probability estimator, can improve on using either component technique alone when used for one-class classification. We also compare the method to one-class classification using support vector machines.

year: 2008

title: Field data collection for implementation of Supercapacitor Assisted LED Lighting (SCALED)

authors: Norbu, Tenzin

subjects: Renewable energy

abstract: With the increasing impact of global warming, climate change is becoming the biggest threat for all life on our planet. The conventional way of generating electricity from the burning of fossil fuels releases significant amounts of carbon dioxide to the atmosphere, which contributes to the rise in the earth’s temperature. Moreover, fossil fuels are being consumed very rapidly and we now have limited resources, which need to be monitored to face future energy demands. The development of renewable energy sources, such as solar power, is a rapidly growing technology. With the extensive research and investment in this industry at present, in the near future solar power will be one of our leading renewable energy sources. Furthermore, as solar panels directly produce direct current (DC), they can be directly tied to a DC microgrid without requiring any power converter, thereby minimizing losses and increasing efficiency.
The supercapacitor assisted light emitting diode (SCALED) converter is one of the new circuit techniques under development for low voltage light emitting diode (LED) systems at the University of Waikato. In this circuit, an LED is connected in series with the supercapacitor bank forming part of a resistor-capacitor (RC) charging loop. This is to avoid energy losses in the RC charging loop, which can create, in the worst case, a 50% loss. As the commonly used 12 V LEDs are internally DC operated devices, SCALED will be applicable in DC microgrids, which are the emerging technology in low voltage distribution systems.
The groundwork for this project requires various solar-related field data collection and simulations for the successful implementation of this innovative technique. Unlike a conventional power supply, solar power output directly depends on the solar irradiance level, which is very unpredictable. Given the unique behaviour of solar panel output, starting with a near constant current behaviour and changing over to a practical voltage source with an approximately constant array resistance, combining a supercapacitor bank and an LED lamp will be a challenge in developing the SCALED topology. In addition, proper field measurements and analysis of these characteristics are essential to develop more efficient and reliable SCALED circuits for DC microgrid applications.

text: Field data collection for implementation of Supercapacitor Assisted LED Lighting (SCALED) With the increasing impact of global warming, climate change is becoming the biggest threat for all life on our planet. The conventional way of generating electricity from the burning of fossil fuels releases significant amounts of carbon dioxide to the atmosphere, which contributes to the rise in the earth’s temperature. Moreover, fossil fuels are being consumed very rapidly and we now have limited resources, which need to be monitored to face future energy demands. The development of renewable energy sources, such as solar power, is a rapidly growing technology. With the extensive research and investment in this industry at present, in the near future solar power will be one of our leading renewable energy sources. Furthermore, as solar panels directly produce direct current (DC), they can be directly tied to a DC microgrid without requiring any power converter, thereby minimizing losses and increasing efficiency.
The supercapacitor assisted light emitting diode (SCALED) converter is one of the new circuit techniques under development for low voltage light emitting diode (LED) systems at the University of Waikato. In this circuit, an LED is connected in series with the supercapacitor bank forming part of a resistor-capacitor (RC) charging loop. This is to avoid energy losses in the RC charging loop, which can create, in the worst case, a 50% loss. As the commonly used 12 V LEDs are internally DC operated devices, SCALED will be applicable in DC microgrids, which are the emerging technology in low voltage distribution systems.
The groundwork for this project requires various solar-related field data collection and simulations for the successful implementation of this innovative technique. Unlike a conventional power supply, solar power output directly depends on the solar irradiance level, which is very unpredictable. Given the unique behaviour of solar panel output, starting with a near constant current behaviour and changing over to a practical voltage source with an approximately constant array resistance, combining a supercapacitor bank and an LED lamp will be a challenge in developing the SCALED topology. In addition, proper field measurements and analysis of these characteristics are essential to develop more efficient and reliable SCALED circuits for DC microgrid applications.

year: 2018

title: 'Closing the Gaps': From postcolonialism to Kaupapa Māori and beyond.

authors: Mahuika, Nepia

subjects: New Zealand

abstract: The article discusses New Zealand history, particularly examining Māori theories and interpretations of history. It considers postcolonial theory and Kaupapa Māori theory. The author comments on the government policy of "closing the gaps," referring to efforts to improve the conditions of underachieving New Zealand groups. He also reflects on Mātauranga, a Māori concept concerning knowledge. The history and oral tradition of the people of the Māori iwi, or social unit, of Ngati Porou is also discussed.

text: 'Closing the Gaps': From postcolonialism to Kaupapa Māori and beyond. The article discusses New Zealand history, particularly examining Māori theories and interpretations of history. It considers postcolonial theory and Kaupapa Māori theory. The author comments on the government policy of "closing the gaps," referring to efforts to improve the conditions of underachieving New Zealand groups. He also reflects on Mātauranga, a Māori concept concerning knowledge. The history and oral tradition of the people of the Māori iwi, or social unit, of Ngati Porou is also discussed.

year: 2011