COMSOL’s New Thermoacoustics Interface and Computationally Efficient Alternative Formulations for FEM

Three efficient alternatives to the model in COMSOL’s thermoacoustics interface are presented. The higher efficiency of these models are explained from theory and are demonstrated by means of two examples

A finite element for viscothermal wave propagation

The well known wave equation describes isentropic wave propagation. In this equation, non-isentropic\ud boundary layer effects are neglected. This is allowed if the characteristic dimensions of the acoustic domain\ud are large with respect to the thickness of the boundary layers. However, in small acoustic devices such as\ud hearing aid loudspeakers, the boundary layer effects are significant and can not be neglected. A model that\ud describes viscothermal wave propagation is needed to model such devices.\ud For viscothermal wave propagation, the compressibility of air depends on the thermal behavior that can\ud range from adiabatic to isothermal. Moreover, the propagation behavior can range from propagation with\ud negligible viscosity to propagation with negligible inertia (Stokes flow). This complete range is accurately\ud described by the low reduced frequency model. This model’s major drawback is that it is only defined for\ud simple geometries such as thin layers and narrow tubes. It is not valid for arbitrary geometries.\ud To overcome this drawback, a three dimensional viscothermal finite element has been developed. Like the\ud LRF model, it covers the complete range from isothermal Stokes flow to isentropic acoustics. As opposed to\ud the LRF model, the viscothermal finite element can be used to analyze complicated geometries.\ud This paper presents the weak formulation of the finite element. Furthermore, two examples are presented in\ud which the results of the finite element models are compared to measurements

A two step viscothermal acoustic FE method

Previously, the authors presented a finite element for viscothermal acoustics. This element has the velocity vector, the temperature and the pressure as degrees of freedom. It can be used, for example, to model sound propagation in miniature acoustical transducers. Unfortunately, the large number of coupled degrees of freedom can make the models big and time consuming to solve. A method with reduced calculation time has been developed. It is possible to partially decouple the temperature degree of freedom, as result of the differences in the characteristic length scales of acoustics and heat conduction. This leads to a method that uses two sequential steps. In the first step, a scalar field containing information about the thermal effects is calculated (not the temperature). This is a relatively small FE calculation. In the second step, the actual viscothermal acoustical equations are solved. This calculation uses the field calculated in the first step and has the velocity vector and the pressure as the degrees of freedom. The temperature is not a degree of freedom anymore, but it can be easily calculated in a post processing step. The required computational effort is reduced significantly, while the difference in the results, compared to the fully coupled method, is negligible. Along with the theoretical basis for the method, a specific FE calculation is presented to illustrate its accuracy and improvement in calculation time

An Exploratory Case Study into Understanding Teaching Practice and Towards Enhancing Transformative Learning and Graduate Employability at TU Dublin

This research focuses on understanding and enhancing the educational practice towards using pedagogies like transformative learning to enhance graduate employability at a new technological university, TU Dublin, during the coronavirus (COVID-19) pandemic. It was found that teaching practice depends significantly on the lecturer, the discipline area, the graduate skills that are sought after in each module and discipline, and the context of the delivery. The PAGE (Pedagogy Assisting Graduate Employability) framework developed from this research, aims to visualise the connection between the teaching process, pedagogy, and graduate employability. Application of the framework will offer insight into how each unique lecturer shapes their own teaching in their context and how development towards pedagogy-based teaching can be further enhanced and encouraged. Four focus groups with lecturers and documentary analysis of books of modules were undertaken across a purposefully selected sample that included a range of disciplines and university campuses to further understand current teaching practice. The PAGE educational framework visualises the connection between lecturer-based pedagogies, such as transformative learning, and student-based graduate employability. A first draft framework was evaluated by lecturers with an affinity for educational development, to result in more insight into the application and possibility to embed and use the framework in day-to-day teaching practice. A second version of the PAGE framework was developed, and alignment was sought with local, national, and international educational policy and directions and plans towards the development of education

Hyperthermia, thermotolerance and topoisomerase II inhibitors.

The cytoxicity of both intercalating (m-AMSA) and non-intercalating (VP16, VM26) topoisomerase II-targeting drugs is thought to occur via trapping DNA topoisomerase II on DNA in the form of cleavable complexes. First, analysis of cleavable complexes (detected as DNA double-strand breaks) by pulsed-field gel electrophoresis confirmed the correlation between cleavable complex formation and cytotoxicity of three topoisomerase-targeting drugs in HeLa S3 cells (the order of effects being VM26 > m-AMSA > VP16). In contrast to many antineoplastic agents, hyperthermic treatments were found to protect cells against the toxicity of all three topoisomerase II drugs. Hyperthermia treatment does not alter drug accumulation but reduces the ability of the drug-topoisomerase II complex to form the cleavable complexes. Nuclear protein aggregation induced by heat at the sites of topoisomerase II-DNA interaction may explain such an effect. In thermotolerant cells, the toxic effects of VP16 but not m-AMSA were reduced. For both drugs, however, the status of thermotolerance did not affect cleavable complex formation by the drugs. Thus, protection against VP-16 toxicity seems not to be associated with heat-induced activation of the P-gp 170 pump or altered topoisomerase II-DNA interactions. Rather, a protective (heat shock protein mediated?) mechanism against non-intercalating topoisomerase II drugs seems to occur at a stage after DNA-drug interaction. Finally, heat treatment before topoisomerase II drug treatment reduced toxicity and cleavable complex formation in thermotolerant cells to about the same extent as in non-tolerant cells, consistent with the presumption of nuclear protein aggregation being responsible for this effect