Elliptical side resonators for broadband noise reduction: theory and experiments

Previous research of the authors pointed out that side-resonators can be applied to reduce fan noise. However, the noise reduction capabilities of most resonator geometries, e.g. tube resonators, cylindrical resonators (cylindrical air layers) and circular resonators (disc shaped air layers), are relatively narrow banded. This is disadvantageous in case resonators are used in combination with a noise source that emits broadband noise or tonal noise at varying frequencies (for instance a speed controlled fan). It was found that the choice of the resonator geometry influences the broadband reduction capabilities (circular resonators offering the best broadband reduction capabilities). In the present study, it is investigated to what extent elliptical resonators, consisting of an elliptically shaped air layer, can be used to achieve broadband noise reduction. A semi-analytical model is proposed that describes the wave propagation in the elliptically shaped air layer. This model is connected to the analytical solution for wave propagation in a tube. The dimensions of the elliptical resonator can be optimized for broadband\ud noise reduction using this model. In addition, an experimental setup was built to verify\ud the semi-analytical model of the elliptical resonator

An acoustic finite element including viscothermal effects

In acoustics it is generally assumed that viscous- en thermal boundary layer effects play a minor role in the propagation of sound waves. Hence, these effects are neglected in the basic set of equations describing the sound field. However, for geometries that include small confinements of air or thin air layers, this assumption is not valid. Special models that include viscous and thermal effects are available (for example the Low Reduced Frequency model) but only for a limited number of geometries. To overcome these limitations and provide a solution that can be used for arbitrary geometries, an acoustic finite (2D) element that includes viscous and thermal effects is developed. The model is based on the linearized Navier stokes equations (including shear), the equation of continuity, the equation of state for an ideal gas and the energy equation. The method of weighed residuals is used in combination with a mixed formulation of pressure, temperature and particle velocity degrees of freedom. The results of the developed element code are compared with the results of an existing (analytical) Low Reduced Frequency solution and a viscothermal element that was found in literature

Exploration of an agenda for transparency in the construction industry

Purpose In enhancing the market operation of the building sector, transparency is of great importance. The objective of this article is to propose an inventory of aspects of the relationships between public clients and executing parties that have the most urgent need for greater transparency. Methodology / approach The main methods used include a conceptual analysis and twenty interviews with managers of various organisations in the construction industry. Findings Based on this study, four essential points for transparency have been determined: openness about risks and costs, measuring of quality-price ratios, reasons for award or rejection and enhancement of the reputation mechanism. Research limitations / implications This study takes the Dutch context as a reference point for the analysis. When the findings are used also in other settings, it is necessary to address the differences in characteristics of the building sector. Practical implications The essential points for transparency addressed in this paper have consequences for especially the interaction between public clients and executing parties. Furthermore, conditions for transparency - like possibilities to judge quality in a more robust and transparent manner and methods for enhancing the reputation mechanism - point at necessary future research for improving transparency in the construction industry. Originality / value of the paper The Dutch construction industry is working through a transition process focused on improving its market operation, integral processes and societal added value. In this transition, transparency between clients and executing parties is of great importance.Transparency; construction sector; trust; reputation; integrity

Reduction of fan noise bymeans of (circular) side-resonators; theory and experiment

One of the main noise sources in computers are the cooling fans. An important aspect of the noise they generate is tonal noise produced at the rotational frequency of the fan, the blade passing frequency (BPF), and its higher harmonics. Previous research pointed out that so-called side resonators can be applied successfully to reduce this tonal noise. A variety of side resonator geometries is available. A model describing viscothermal wave propagation in a circular side-resonator and the connected duct and the preliminary results of a parameter study of that model where presented previously. The experimental verification of the model is presented here

Achieving equity through 'gender autonomy': the challenges for VET policy and practice

This paper is based on research carried out in an EU Fifth Framework project on 'Gender and Qualification'. The research partners from five European countries investigated the impact of gender segregation in European labour markets on vocational education and training, with particular regard to competences and qualifications. The research explored the part played by gender in the vocational education and training experiences of (i) young adults entering specific occupations in child care, electrical engineering and food preparation/service (ii) adults changing occupations

Selection of reference genes for quantitative RT-PCR studies in Rhipicephalus (Boophilus) microplus and Rhipicephalus appendiculatus ticks and determination of the expression profile of Bm86

<p>Abstract</p> <p>Background</p> <p>For accurate and reliable gene expression analysis, normalization of gene expression data against reference genes is essential. In most studies on ticks where (semi-)quantitative RT-PCR is employed, normalization occurs with a single reference gene, usually β-actin, without validation of its presumed expression stability. The first goal of this study was to evaluate the expression stability of commonly used reference genes in <it>Rhipicephalus appendiculatus </it>and <it>Rhipicephalus (Boophilus) microplus </it>ticks. To demonstrate the usefulness of these results, an unresolved issue in tick vaccine development was examined. Commercial vaccines against <it>R. microplus </it>were developed based on the recombinant antigen Bm86, but despite a high degree of sequence homology, these vaccines are not effective against <it>R. appendiculatus</it>. In fact, Bm86-based vaccines give better protection against some tick species with lower Bm86 sequence homology. One possible explanation is the variation in Bm86 expression levels between <it>R. microplus </it>and <it>R. appendiculatus</it>. The most stable reference genes were therefore used for normalization of the Bm86 expression profile in all life stages of both species to examine whether antigen abundance plays a role in Bm86 vaccine susceptibility.</p> <p>Results</p> <p>The transcription levels of nine potential reference genes: β-actin (ACTB), β-tubulin (BTUB), elongation factor 1α (ELF1A), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), glutathione S-transferase (GST), H3 histone family 3A (H3F3A), cyclophilin (PPIA), ribosomal protein L4 (RPL4) and TATA box binding protein (TBP) were measured in all life stages of <it>R. microplus </it>and <it>R. appendiculatus</it>. ELF1A was found to be the most stable expressed gene in both species following analysis by both geNorm and Normfinder software applications, GST showed the least stability. The expression profile of Bm86 in <it>R. appendiculatus </it>and <it>R. microplus </it>revealed a more continuous Bm86 antigen abundance in <it>R. microplus </it>throughout its one-host life cycle compared to the three-host tick <it>R. appendiculatus </it>where large variations were observed between different life stages.</p> <p>Conclusion</p> <p>Based on these results, ELF1A can be proposed as an initial reference gene for normalization of quantitative RT-PCR data in whole <it>R. microplus </it>and <it>R. appendiculatus </it>ticks. The observed differences in Bm86 expression profile between the two species alone can not adequately explain the lack of a Bm86 vaccination effect in <it>R. appendiculatus</it>.</p

Game-based meditation therapy to improve posttraumatic stress and neurobiological stress systems in traumatized adolescents:Protocol for a randomized controlled trial

Background: Many adolescents in residential care have been exposed to prolonged traumatic experiences such as violence, neglect, or abuse. Consequently, they suffer from posttraumatic stress. This not only negatively affects psychological and behavioral outcomes (eg, increased anxiety, depression, and aggression) but also has adverse effects on physiological outcomes, in particular on their neurobiological stress systems. Although current evidence-based treatment options are effective, they have their limitations. An alternative to traditional trauma treatment is meditation-based treatment that focuses on stress regulation and relaxation. Muse is a game-based meditation intervention that makes use of adolescents’ intrinsic motivation. The neurofeedback element reinforces relaxation abilities. Objective: This paper describes the protocol for a randomized controlled trial in which the goal is to examine the effectiveness of Muse (InteraXon Inc) in reducing posttraumatic stress and normalizing neurobiological stress systems in a sample of traumatized adolescents in residential care. Methods: This will be a multicenter, multi-informant, and multimethod randomized controlled trial. Participants will be adolescents (N=80), aged 10 to 18 years, with clinical levels of posttraumatic symptoms, who are randomized to receive either the Muse therapy sessions and treatment as usual (intervention) or treatment as usual alone (control). Data will be collected at 3 measurement instances: pretest (T1), posttest (T2), and at 2-month follow-up. Primary outcomes will be posttraumatic symptoms (self-report and mentor report) and stress (self-report) at posttest. Secondary outcomes will be neurobiological stress parameters under both resting and acute stress conditions, and anxiety, depression, and aggression at posttest. Secondary outcomes also include all measures at 2-month follow-up: posttraumatic symptoms, stress, anxiety, depression aggression, and neurobiological resting parameters. Results: The medical-ethical committee Arnhem-Nijmegen (NL58674.091.16) approved the trial on November 15, 2017. The study was registered on December 2, 2017. Participant enrollment started in January 2018, and the results of the study are expected to be published in spring or summer 2021. Conclusions: Study results will demonstrate whether game-based meditation therapy improves posttraumatic stress and neurobiological stress systems, and whether it is more effective than treatment as usual alone for traumatized adolescents