title: Hall current effects in dynamic magnetic reconnection solutions

authors: Craig, Ian J.D.

subjects: mathematics

abstract: The impact of Hall current contributions on flow driven planar magnetic merging solutions is discussed. The Hall current is important if the dimensionless Hall parameter (or normalized ion skin depth) satisfies cH>η where η is the inverse Lundquist number for the plasma. A dynamic analysis of the problem shows, however, that the Hall current initially manifests itself, not by modifying the planar reconnection field, but by inducing a non-reconnecting perpendicular "separator" component in the magnetic field. Only if the stronger condition c2/H > η is satisfied can Hall currents be expected to affect the planar merging. These analytic predictions are then tested by performing a series of numerical experiments in periodic geometry, using the full system of planar magnetohydrodynamic (MHD) equations. The numerical results confirm that the nature of the merging changes dramatically when the Hall coupling satisfies c2/H > η. In line with the analytic treatment of sheared reconnection, the coupling provided by the Hall term leads to the emergence of multiple current layers that can enhance the global Ohmic dissipation at the expense of the reconnection rate. However, the details of the dissipation depend critically on the symmetries of the simulation, and when the merging is "head-on" (i.e., comprises fourfold symmetry) the reconnection rate can be enhanced.

text: Hall current effects in dynamic magnetic reconnection solutions The impact of Hall current contributions on flow driven planar magnetic merging solutions is discussed. The Hall current is important if the dimensionless Hall parameter (or normalized ion skin depth) satisfies cH>η where η is the inverse Lundquist number for the plasma. A dynamic analysis of the problem shows, however, that the Hall current initially manifests itself, not by modifying the planar reconnection field, but by inducing a non-reconnecting perpendicular "separator" component in the magnetic field. Only if the stronger condition c2/H > η is satisfied can Hall currents be expected to affect the planar merging. These analytic predictions are then tested by performing a series of numerical experiments in periodic geometry, using the full system of planar magnetohydrodynamic (MHD) equations. The numerical results confirm that the nature of the merging changes dramatically when the Hall coupling satisfies c2/H > η. In line with the analytic treatment of sheared reconnection, the coupling provided by the Hall term leads to the emergence of multiple current layers that can enhance the global Ohmic dissipation at the expense of the reconnection rate. However, the details of the dissipation depend critically on the symmetries of the simulation, and when the merging is "head-on" (i.e., comprises fourfold symmetry) the reconnection rate can be enhanced.

year: 2003-04-16

title: Testing the boundaries of the middle voice: Observations from English and Romanian

authors: Calude, Andreea S.

subjects: Social Sciences

abstract: The middle voice has received ample attention in the literature, yet the precise boundary between middle voice and other related constructions still remains elusive. For example, do sentences like Mary slept (*herself) well last night and Mary washed (herself) thoroughly and expertly belong to the middle voice or the reflexive domain, or are they simply intransitive one-participant structures? While ambiguity between reflexive and middles has been noted by (Kemmer, Suzanne. 1993. The middle voice. Amsterdam & Philadelphia: John Benjamins.), I show that the problem is more widespread. Depending on the marking patterns available in a given language, such ambiguities can occur between middles and prototypical intransitive one-participant events, or between middles and reflexives. Using data from two languages with distinct marking patterns – English (a language with a reflexive marker but no middle marker) and Romanian (a language with one marker of each type) – I discuss the possibility of distinguishing middles from other related constructions. In English, it is shown that the him/herself test can be used to distinguish direct middles from intransitive one-participant events. In Romanian, we see middle and reflexive markers used together in the same construction without contradiction, bringing together both middle and reflexive semantics (as well as marking). In agreement with (Maldonado, Ricardo. 2000. Spanish reflexives. In Zygmunt Frajzyngier & Traci Walker (eds.), Reflexives: Forms and functions, 153–185. Amsterdam & Philadelphia: John Benjamins.) and (Manney, Linda. 2001. Middle voice in Modern Greek: Meaning and function of a morphoyntactic category. Amsterdam &Philadelphia: John Benjamins.), the account given here supports the view of the middle voice as a unified phenomenon, and following (Maldonado, Ricardo. 2009. Middle as a basic voice system. In Lilian Guerrero, Ibáñez Sergio & Belloro Valeria (eds.), Studies in role and reference grammar. México: Instituto de Investigaciones Filológicas, UNAM.), the main function of the middle is to profile the core properties of events (but not necessarily to reduce the relative elaboration of participants, as proposed by Kemmer, Suzanne. 1993. The middle voice. Amsterdam &Philadelphia: John Benjamins.). So, unlike active and passive voice which concern the focusing of various participants (namely, Agents and Patients, respectively), the middle voice focuses the event itself.

text: Testing the boundaries of the middle voice: Observations from English and Romanian The middle voice has received ample attention in the literature, yet the precise boundary between middle voice and other related constructions still remains elusive. For example, do sentences like Mary slept (*herself) well last night and Mary washed (herself) thoroughly and expertly belong to the middle voice or the reflexive domain, or are they simply intransitive one-participant structures? While ambiguity between reflexive and middles has been noted by (Kemmer, Suzanne. 1993. The middle voice. Amsterdam & Philadelphia: John Benjamins.), I show that the problem is more widespread. Depending on the marking patterns available in a given language, such ambiguities can occur between middles and prototypical intransitive one-participant events, or between middles and reflexives. Using data from two languages with distinct marking patterns – English (a language with a reflexive marker but no middle marker) and Romanian (a language with one marker of each type) – I discuss the possibility of distinguishing middles from other related constructions. In English, it is shown that the him/herself test can be used to distinguish direct middles from intransitive one-participant events. In Romanian, we see middle and reflexive markers used together in the same construction without contradiction, bringing together both middle and reflexive semantics (as well as marking). In agreement with (Maldonado, Ricardo. 2000. Spanish reflexives. In Zygmunt Frajzyngier & Traci Walker (eds.), Reflexives: Forms and functions, 153–185. Amsterdam & Philadelphia: John Benjamins.) and (Manney, Linda. 2001. Middle voice in Modern Greek: Meaning and function of a morphoyntactic category. Amsterdam &Philadelphia: John Benjamins.), the account given here supports the view of the middle voice as a unified phenomenon, and following (Maldonado, Ricardo. 2009. Middle as a basic voice system. In Lilian Guerrero, Ibáñez Sergio & Belloro Valeria (eds.), Studies in role and reference grammar. México: Instituto de Investigaciones Filológicas, UNAM.), the main function of the middle is to profile the core properties of events (but not necessarily to reduce the relative elaboration of participants, as proposed by Kemmer, Suzanne. 1993. The middle voice. Amsterdam &Philadelphia: John Benjamins.). So, unlike active and passive voice which concern the focusing of various participants (namely, Agents and Patients, respectively), the middle voice focuses the event itself.

year: 2017

title: Distributed agent-centric system for indigenous data sovereignty

authors: Noovao, Setephano

subjects: holochain

abstract: The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

text: Distributed agent-centric system for indigenous data sovereignty The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

year: 2024