title: A supercapacitor assisted technique for reducing losses in the input loop of an inverter system for solar PV applications

authors: Naligama, Chamila Anuradha

subjects: switching converters

abstract: This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter's overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.

text: A supercapacitor assisted technique for reducing losses in the input loop of an inverter system for solar PV applications This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter's overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.

year: 2024

title: Syntax-driven argument identification and multi-argument classification for semantic role labeling

authors: Lin, Chi-San Althon

subjects: Semantic Role Labeling

abstract: Semantic role labeling is an important stage in systems for Natural Language Understanding.  The basic problem is one of identifying who did what to whom for each predicate in a sentence.  Thus labeling is a two-step process: identify constituent phrases that are arguments to a predicate, then label those arguments with appropriate thematic roles.

Existing systems for semantic role labeling use machine learning methods to assign roles one-at-a-time to candidate arguments.  There are several drawbacks to this general approach.  First, more than one candidate can be assigned the same role, which is undesirable.  Second, the search for each candidate argument is exponential with respect to the number of words in the sentence.  Third, single-role assignment cannot take advantage of dependencies known to exist between semantic roles of predicate arguments, such as their relative juxtaposition.  And fourth, execution times for existing algorithm are excessive, making them unsuitable for real-time use.

This thesis seeks to obviate these problems by approaching semantic role labeling as a multi-argument classification process.  It observes that the only valid arguments to a predicate are unembedded constituent phrases that do not overlap that predicate.  Given that semantic role labeling occurs after parsing, this thesis proposes an algorithm that systematically traverses the parse tree when looking for arguments, thereby eliminating the vast majority of impossible candidates.   

Moreover, instead of assigning semantic roles one at a time, an algorithm is proposed to assign all labels simultaneously; leveraging dependencies between roles and eliminating the problem of duplicate assignment.

Experimental results are provided as evidence to show that a combination of the proposed argument identification and multi-argument classification algorithms outperforms all existing systems that use the same syntactic information.

text: Syntax-driven argument identification and multi-argument classification for semantic role labeling Semantic role labeling is an important stage in systems for Natural Language Understanding.  The basic problem is one of identifying who did what to whom for each predicate in a sentence.  Thus labeling is a two-step process: identify constituent phrases that are arguments to a predicate, then label those arguments with appropriate thematic roles.

Existing systems for semantic role labeling use machine learning methods to assign roles one-at-a-time to candidate arguments.  There are several drawbacks to this general approach.  First, more than one candidate can be assigned the same role, which is undesirable.  Second, the search for each candidate argument is exponential with respect to the number of words in the sentence.  Third, single-role assignment cannot take advantage of dependencies known to exist between semantic roles of predicate arguments, such as their relative juxtaposition.  And fourth, execution times for existing algorithm are excessive, making them unsuitable for real-time use.

This thesis seeks to obviate these problems by approaching semantic role labeling as a multi-argument classification process.  It observes that the only valid arguments to a predicate are unembedded constituent phrases that do not overlap that predicate.  Given that semantic role labeling occurs after parsing, this thesis proposes an algorithm that systematically traverses the parse tree when looking for arguments, thereby eliminating the vast majority of impossible candidates.   

Moreover, instead of assigning semantic roles one at a time, an algorithm is proposed to assign all labels simultaneously; leveraging dependencies between roles and eliminating the problem of duplicate assignment.

Experimental results are provided as evidence to show that a combination of the proposed argument identification and multi-argument classification algorithms outperforms all existing systems that use the same syntactic information.

year: 2007

title: Indigenous knowledge, methodology and mayhem: What is the role of methodology in producing indigenous insights? A discussion from Mātauranga Māori

authors: Smith, Linda Tuhiwai

abstract: The emergence of an academic discourse called Indigenous knowledge internationally, and mātauranga Māori in Aotearoa New Zealand, presents some substantive challenges to concepts of knowing and being, of knowledge creation, knowledge work and the making of meaning. These challenges engage us across philosophical, disciplinary, institutional, inter-generational, territorial and community boundaries, presenting an opportunity to imagine this field anew, and the theories and methodologies that inform contemporary Māori or Indigenous Studies. This article raises some discussion about ‘research methodologies’ being used when discussing mātauranga Māori and Indigenous knowledge (hereafter referred to as IK mātauranga). Research methodologies are often associated with specific disciplines of knowledge and viewed as the primary if not singular way in which knowledge is generated. Arguably, IK mātauranga occupies a different knowledge space from traditional academic disciplines, including their transdisciplinary interstices. This article speaks to a gnawing sense that mayhem is at play, as the academic work around IK mātauranga begins to consolidate and become institutionalised away from its indigenous communities and contexts, where it began and where it still informs identities, ways of living and being.

text: Indigenous knowledge, methodology and mayhem: What is the role of methodology in producing indigenous insights? A discussion from Mātauranga Māori The emergence of an academic discourse called Indigenous knowledge internationally, and mātauranga Māori in Aotearoa New Zealand, presents some substantive challenges to concepts of knowing and being, of knowledge creation, knowledge work and the making of meaning. These challenges engage us across philosophical, disciplinary, institutional, inter-generational, territorial and community boundaries, presenting an opportunity to imagine this field anew, and the theories and methodologies that inform contemporary Māori or Indigenous Studies. This article raises some discussion about ‘research methodologies’ being used when discussing mātauranga Māori and Indigenous knowledge (hereafter referred to as IK mātauranga). Research methodologies are often associated with specific disciplines of knowledge and viewed as the primary if not singular way in which knowledge is generated. Arguably, IK mātauranga occupies a different knowledge space from traditional academic disciplines, including their transdisciplinary interstices. This article speaks to a gnawing sense that mayhem is at play, as the academic work around IK mātauranga begins to consolidate and become institutionalised away from its indigenous communities and contexts, where it began and where it still informs identities, ways of living and being.

year: 2016