Reflecting boundary conditions for interferometry by multidimensional deconvolution.

In an acoustical context, interferometry takes advantage of existing (ambient) wavefield recordings by turning receivers into so-called "virtual sources." The medium's response to these virtual sources can be harnessed to image that medium. Most interferometric applications, however, suffer from the fact that the retrieved virtual-source responses deviate from the true medium responses. The accrued artefacts are often predominantly due to a non-isotropic illumination of the medium of interest, and prohibit accurate interferometric imaging. Recently, it has been shown that illumination-related artefacts can be removed by means of a so-called multidimensional deconvolution (MDD) process. However, the current MDD formulation, and hence method, relies on separation of waves traveling inward and outward through the boundary of the medium of interest. As a consequence, it is predominantly useful when receivers are illuminated from one side only. This puts constraints on the applicability of the current MDD formulation to omnidirectional wavefields. In this paper, a modified formulation of the theory underlying interferometry by MDD is presented. This modified formulation eliminates the requirement to separate inward and outward propagating wavefields and, consequently, holds promise for the application of MDD to non-isotropic, omnidirectional wavefields.

The significance of the evanescent spectrum in structure-waveguide interaction problems.

Modal decomposition is often applied in elastodynamics and acoustics for the solution of problems related to propagation of mechanical disturbances in waveguides. One of the key elements of this method is the solution of an eigenvalue problem for obtaining the roots of the dispersion equation, which signify the wavenumbers of the waves that may exist in the system. For non-dissipative media, the wavenumber spectrum consists of a finite number of real roots supplemented by infinitely many imaginary and complex ones. The former refer to the propagating modes in the medium, whereas the latter constitute the so-called evanescent spectrum. This study investigates the significance of the evanescent spectrum in structure-waveguide interaction problems. Two cases are analysed, namely, a beam in contact with a fluid layer and a cylindrical shell interacting with an acousto-elastic waveguide. The first case allows the introduction of a modal decomposition method and the establishment of appropriate criteria for the truncation of the modal expansions in a simple mathematical framework. The second case describes structure-borne wave radiation in an offshore environment during the installation of a pile with an impact hammer-a problem that has raised serious concerns in recent years due to the associated underwater noise pollution.

Quality indicators for all dimensions of infertility care quality: consensus between professionals and patients.

STUDY QUESTION: What is the relative importance of the six dimensions of quality of care according to different stakeholders and can a quality indicator set address all six quality dimensions and incorporate the views from professionals working in different disciplines and from patients? SUMMARY ANSWER: Safety, effectiveness and patient centeredness were the most important quality dimensions. All six quality dimensions can be assessed with a set of 24 quality indicators, which is face valid and acceptable according to both professionals from different disciplines and patients. WHAT IS KNOWN ALREADY: To our knowledge, no study has weighted the relative importance of all quality dimensions to infertility care. Additionally, there are very few infertility care-specific quality indicators and no quality indicator set covers all six quality dimensions and incorporated the views of professionals and patients. STUDY DESIGN, SIZE AND DURATION: A three-round iterative Delphi survey including patients and professionals from four different fields, conducted in two European countries over the course of 2011 and 2012. PARTICIPANTS/MATERIALS, SETTINGS AND METHODS: Dutch and Belgian gynaecologists, embryologists, counsellors, nurses/midwifes and patients took part (n = 43 in round 1 and finally 30 in round 3). Respondents ranked the six quality dimensions twice for importance and their agreement was evaluated. Furthermore, in round 1, respondents gave suggestions, which were subsequently uniformly formulated as quality indicators. In rounds 2 and 3, respondents rated the quality indicators for preparedness to measure and for importance (relation to quality and prioritization for benchmarking). Providing feedback allowed selecting indicators based on consensus between stakeholder groups. Measurable indicators, important to all stakeholder groups, were selected for each quality dimension. MAIN RESULTS: All stakeholder groups and most individuals agreed that safety, effectiveness and patient centeredness were the most important quality dimensions. A total of 498 suggestions led to the development of 298 indicators. Professionals were sufficiently prepared to measure 204 of these indicators. Based on importance, 52 (7-15 per dimension; round 2) and finally 24 (4 per dimension; round 3) quality indicators were selected. LIMITATIONS, REASONS FOR CAUTION: The final quality indicator set does not cover the entire care process, but rather takes a 'sample' of each quality dimension. Although the quality indicators are face valid and acceptable, their psychometric characteristics need to be tested by further research. WIDER IMPLICATIONS OF THE FINDINGS: Quality management should focus on safety, effectiveness and patient centeredness of care. Clinics can use the quality indicator set to assess all quality dimensions of their care.