title: Bipenalty method from a frequency domain perspective

authors: Ilanko, Sinniah

subjects: bipenalty method

abstract: In a recent paper, it was shown that for time domain analysis, the simultaneous use of inertial and stiffness type penalty parameters to enforce constraints was found to yield accurate and converging results without causing any stability problems. From a frequency domain perspective, this is somewhat unexpected because the solution converges from below when stiffness penalty parameters are used to model constraints, and the convergence is from above when inertial penalty parameters are used. The purpose of this paper is to explain the effect of the simultaneous use of stiffness and inertial penalty parameters on the natural frequencies of constrained systems. In this work, it is shown that if suitably tuned, the bipenalty approach works well for frequency domain analysis also, and that with two different tuned set of stiffness and inertial penalty parameters, bounded solutions to the natural frequencies of constrained systems may be obtained. The method is applicable for any linear eigenvalue problem.

text: Bipenalty method from a frequency domain perspective In a recent paper, it was shown that for time domain analysis, the simultaneous use of inertial and stiffness type penalty parameters to enforce constraints was found to yield accurate and converging results without causing any stability problems. From a frequency domain perspective, this is somewhat unexpected because the solution converges from below when stiffness penalty parameters are used to model constraints, and the convergence is from above when inertial penalty parameters are used. The purpose of this paper is to explain the effect of the simultaneous use of stiffness and inertial penalty parameters on the natural frequencies of constrained systems. In this work, it is shown that if suitably tuned, the bipenalty approach works well for frequency domain analysis also, and that with two different tuned set of stiffness and inertial penalty parameters, bounded solutions to the natural frequencies of constrained systems may be obtained. The method is applicable for any linear eigenvalue problem.

year: 2013

title: Thermomechanical processing of cost-affordable powder metallurgy Ti-5Fe alloys from the blended elemental approach: Microstructure, tensile deformation behavior, and failure

authors: Romero Villarreal, Carlos

subjects: Science & Technology

abstract: The development of cost-affordable Ti alloys is key for the application of Ti in other industries like the automobile sector. Therefore, a combination of powder metallurgy (PM) and low-cost compositions is an interesting approach. In this article, a cost-affordable PM Ti-5Fe alloy is processed following the blended elemental route and extruded at high temperature to remove porosity. Different extrusion temperatures and heat treatments (i.e., solution treatment and aging, STA) are performed to obtain ultrafine microstructures, and their effect on the mechanical behavior is studied. For extrusions in the β phase, microstructures consist of coarse lamellar colonies, resulting in alloys with improved properties compared to the as-sintered alloy but still lacking toughness due to the failure happening just after necking onset. Extruding in the α + β phase results in a bimodal microstructure of fine elongated primary α and coarse lamellar colonies, and the alloy becomes tougher. STA with aging below the eutectoid temperature of 590 °C leads to a hard but brittle alloy, whereas STA with aging above it results in alloys with strength comparable to the as-extruded conditions and enhanced ductility.

text: Thermomechanical processing of cost-affordable powder metallurgy Ti-5Fe alloys from the blended elemental approach: Microstructure, tensile deformation behavior, and failure The development of cost-affordable Ti alloys is key for the application of Ti in other industries like the automobile sector. Therefore, a combination of powder metallurgy (PM) and low-cost compositions is an interesting approach. In this article, a cost-affordable PM Ti-5Fe alloy is processed following the blended elemental route and extruded at high temperature to remove porosity. Different extrusion temperatures and heat treatments (i.e., solution treatment and aging, STA) are performed to obtain ultrafine microstructures, and their effect on the mechanical behavior is studied. For extrusions in the β phase, microstructures consist of coarse lamellar colonies, resulting in alloys with improved properties compared to the as-sintered alloy but still lacking toughness due to the failure happening just after necking onset. Extruding in the α + β phase results in a bimodal microstructure of fine elongated primary α and coarse lamellar colonies, and the alloy becomes tougher. STA with aging below the eutectoid temperature of 590 °C leads to a hard but brittle alloy, whereas STA with aging above it results in alloys with strength comparable to the as-extruded conditions and enhanced ductility.

year: 2020

title: An exploration of different outlooks on science: towards an understanding of the under-representation of girls, and of Maori and Pacific Island students, in science

authors: Stead, Keith Eric

abstract: The research reported here was undertaken as a supplementary study to the Learning in Science Project conducted at Waikato University (1979-1981) and sought to understand why girls, Maori and Pacific Island students, are under-represented in the sciences. Two distinctive, but complementary, perspectives were developed; one qualitative, the other quantitative, to provide data from which an understanding of the problem was sought.
The qualitative perspective was provided by using a Kelly Repertory Grid methodology and intensive individual interviews with 26 students (and many of their parents) carefully chosen to provide a reasonably heterogeneous sample of students from a variety of different schools, of both sexes, of the three major ethnic groups (European, Maori, and Pacific Island), and from each of the four middle-school form levels (Fl to F4, inclusively).
The quantitative perspective was provided by a series of empirical measures chosen, not only to identify the students for the qualitative sample but also, to investigate particular variables suggested by the literature search to have possible implications for the teaching and learning of science. 
The resultant analyses suggested the sex differences in the students’ outlooks on science could be accounted for by the existence of a broad based ‘gender-related inequality’ in the way science is presented to them by the communication media, home, and school.
Similarly, the ethnic differences in students’ outlooks on science could be accounted for by the ‘cultural inequality’ present in New Zealand society which was identified in the way many of the Polynesian students and their parents, perceived the products, processes, and practitioners of science. 
The simplification presented here masks the complexity of the issues involved but, series of educational within these two broad postulates, a series of educational recommendations was suggested for affecting current educational practices identified as maintaining (or even creating) the existing under-representation of girls, Maori and Pacific Island students in the sciences. 
These included:
(i) Student beliefs about science need to be explored, challenged, modified, and/or extended
(ii) Students’ perceptions of other people’s views need to be identified, explored, challenged and/or extended 
(iii) Teachers’ styles of teaching science need to be examined
(iv) Parents’ own outlooks on science need to be developed.
This research has emphasised the need to have all students, but particularly girls, Maori, and Pacific Island students, develop positive outlooks on science in order that the current imbalance of girls and Polynesians in the sciences be redressed.

text: An exploration of different outlooks on science: towards an understanding of the under-representation of girls, and of Maori and Pacific Island students, in science The research reported here was undertaken as a supplementary study to the Learning in Science Project conducted at Waikato University (1979-1981) and sought to understand why girls, Maori and Pacific Island students, are under-represented in the sciences. Two distinctive, but complementary, perspectives were developed; one qualitative, the other quantitative, to provide data from which an understanding of the problem was sought.
The qualitative perspective was provided by using a Kelly Repertory Grid methodology and intensive individual interviews with 26 students (and many of their parents) carefully chosen to provide a reasonably heterogeneous sample of students from a variety of different schools, of both sexes, of the three major ethnic groups (European, Maori, and Pacific Island), and from each of the four middle-school form levels (Fl to F4, inclusively).
The quantitative perspective was provided by a series of empirical measures chosen, not only to identify the students for the qualitative sample but also, to investigate particular variables suggested by the literature search to have possible implications for the teaching and learning of science. 
The resultant analyses suggested the sex differences in the students’ outlooks on science could be accounted for by the existence of a broad based ‘gender-related inequality’ in the way science is presented to them by the communication media, home, and school.
Similarly, the ethnic differences in students’ outlooks on science could be accounted for by the ‘cultural inequality’ present in New Zealand society which was identified in the way many of the Polynesian students and their parents, perceived the products, processes, and practitioners of science. 
The simplification presented here masks the complexity of the issues involved but, series of educational within these two broad postulates, a series of educational recommendations was suggested for affecting current educational practices identified as maintaining (or even creating) the existing under-representation of girls, Maori and Pacific Island students in the sciences. 
These included:
(i) Student beliefs about science need to be explored, challenged, modified, and/or extended
(ii) Students’ perceptions of other people’s views need to be identified, explored, challenged and/or extended 
(iii) Teachers’ styles of teaching science need to be examined
(iv) Parents’ own outlooks on science need to be developed.
This research has emphasised the need to have all students, but particularly girls, Maori, and Pacific Island students, develop positive outlooks on science in order that the current imbalance of girls and Polynesians in the sciences be redressed.

year: 1984