Achieving a flat, wideband frequency response of a loudspeaker unit by numerical optimization with requirements on its directivity.

This paper demonstrates how significant improvement in frequency response and directivity of a loudspeaker may be obtained by optimizing the local properties of the materials for the diaphragm and surround. Performance is investigated as the considered frequency range and off-axis requirements are progressively expanded. The results are generated by optimizing the values and layout of stiffness, mass, and damping of both the speaker diaphragm and surround. This is accomplished using a density and gradient-based optimization technique in conjunction with a fully coupled finite element model of the loudspeaker and the surrounding acoustic domain. The targeted frequency range is from 600 Hz up to 10 kHz and the range for the directivity is from 0° to 30°. The results show that a completely flat on-axis response is achievable even for very broad frequency ranges and that a reasonably flat response over a wide directivity can be obtained as well. The results presented in this research assume that complete design and production freedom are available.

Structural optimization for nonlinear dynamic response.

Much is known about the nonlinear resonant response of mechanical systems, but methods for the systematic design of structures that optimize aspects of these responses have received little attention. Progress in this area is particularly important in the area of micro-systems, where nonlinear resonant behaviour is being used for a variety of applications in sensing and signal conditioning. In this work, we describe a computational method that provides a systematic means for manipulating and optimizing features of nonlinear resonant responses of mechanical structures that are described by a single vibrating mode, or by a pair of internally resonant modes. The approach combines techniques from nonlinear dynamics, computational mechanics and optimization, and it allows one to relate the geometric and material properties of structural elements to terms in the normal form for a given resonance condition, thereby providing a means for tailoring its nonlinear response. The method is applied to the fundamental nonlinear resonance of a clamped-clamped beam and to the coupled mode response of a frame structure, and the results show that one can modify essential normal form coefficients by an order of magnitude by relatively simple changes in the shape of these elements. We expect the proposed approach, and its extensions, to be useful for the design of systems used for fundamental studies of nonlinear behaviour as well as for the development of commercial devices that exploit nonlinear behaviour.

Impact of p16-overexpression on overall and progression-free survival outcomes in oral cavity squamous cell carcinomas: A semi-national, population-based study.

OBJECTIVES: Human papillomavirus infection and p16-overexpression is a principal cause and favorable prognostic factor for oropharyngeal squamous cell carcinomas but the value as prognostic marker in oral cavity squamous cell carcinomas (OSCC) is undetermined. MATERIALS AND METHODS: All patients diagnosed with OSCC in Eastern Denmark in the period 2008-2014 were enrolled. Survival estimates were evaluated as overall survival (OS) and progression free survival (PFS) by Kaplan-Meier survival curves and multivariate Cox-regression analyses. RESULTS: We included 575 patients from which 13% (n = 69) had p16-positive tumors. The 5-year OS were 55% and 62% for the p16-negative and p16-positive patients, respectively, and the 5-year PFS were 48% and 50%. In a multivariate survival analysis, p16-positivity showed no significant influence on OS (HR: 1.06 [0.67-1.70], p = 0.79) and PFS (HR: 1.11 [0.76-1.63], p = 0.58). CONCLUSION: In this population-based cohort of non-selected OSCC patients, we found no difference in survival outcomes when stratified on p16-overexpression status.

Topology Optimized Architectures with Programmable Poisson's Ratio over Large Deformations.

Topology optimized architectures are designed and printed with programmable Poisson's ratios ranging from -0.8 to 0.8 over large deformations of 20% or more.