open_access
Refine
Publication Type
- Conference Proceeding (17) (remove)
Keywords
- CMS (1)
- PIV (1)
- V&V 40 (1)
- computational modeling and simulation (1)
- mixing ventilation (1)
- model credibility (1)
- plant-based diet (1)
- room airflow (1)
- sustainability (1)
- unsteady ventilation (1)
Mechanical ventilation of buildings is generally based on steadily operating systems. This field is well known and established. But, an approach based on time-varied supply flow rates might improve indoor air quality, comfort, and energy consumption. Typical time-scales of the variation are in the order of seconds or minutes. Until now, the effects of unsteady ventilation scenarios are not fully described and so, reliable dimensioning rules are missing. Hence, with a better understanding of the flow in unsteady ventilation, systems can be calculated and optimised. To understand the effective mechanisms and derive functional relations between the flow field and variation parameters, full-field optical flow measurements are executed with a particle image velocimetry (PIV) system. Experiments are conducted under isothermal conditions in water in a small-scale room model (1.00 m × 0.67 m × 0.46 m) with two swirl ceiling diffusers, Reynolds-scaling assures similarity. In a series of experiments, the effects of different unsteady ventilation strategies on the flow fields are investigated and compared to steady conditions with the same mean exchange rate. Mean exchange rates, signal types, periods, and amplitudes are varied. Time-averaged normalised velocity fields already indicate notable differences between steady and unsteady cases especially for lower exchange rates: the distribution is more homogeneous in unsteady scenarios compared to steady conditions, and low-velocity areas are reduced while the mean velocity of the room increases. So, unsteady ventilation might be beneficial in terms of improved ventilation and energy savings in partial-load operation. Fast Fourier Transformation (FFT) analyses of the mean velocity for each field over the whole series detect the main frequency of the volume flow variation. By dividing the velocity field into smaller areas, this main frequency is still detected especially in the upper part of the room, but side frequencies play a role in the room as well.
The use of computational modeling and simulation (CMS) as a tool for gaining insight into the technical performance and safety of medical devices has emerged continuously over the past years. However, to rely on information and decisions derived from model predictions, it is essential to establish model credibility for the specific context of use. Limited regulatory requirements and lack of consensus on the level of verification and validation activities required result in rare use of CMS as a source of evidence in the medical device approval process. The American Society of Mechanical Engineers (ASME) developed a risk-informed framework to establish appropriate credibility requirements of a computational model: the ASME V&V 40?2018 standard. This paper aims to outline the concepts of this standard and to demonstrate its application using an example from the orthotics field. The necessary steps to establish model credibility for a custom?made 3D printed wrist hand orthosis (WHO) are presented. It is shown that the credibility requirements of each verification and validation activity depend on model risk by applying two different contexts of use to the same computational model.
Introduction: Moving towards a more plant-based dietary pattern would likely be beneficial in terms of a variety of sustainability dimensions.
Methodology: We conducted a 2-year intervention study with six measurement time points (baseline, 10 weeks, 6 months, 1 year, 1½ years, 2 years) in rural northwest Germany. The intervention consisted of a lifestyle programme, and dietary recommendations were to move towards a healthy, plant-based diet. The control group received no intervention. Diet quality was assessed with the healthful plant-based diet index (hPDI).
Results: In the intervention group (n = 67), the 2-year trajectory of hPDI was significantly higher compared to control (n = 39; p 0.001; between-group difference: 5.7 (95% CI 4.0, 7.3) food portions/day; adjusted for baseline). The 2-year trajectory of meat intake was significantly lower in the intervention group (n = 79) compared to control (n = 40; p 0.001; between-group difference: -0.7 (95% CI -0.9, -0.5) portions/day; adjusted for baseline).
Conclusion: Our study confirms that plant-based nutrition education in the general population is likely to result in at least modest dietary improvements in terms of general healthfulness and meat reduction.
Entwicklung eines Konzeptes zur Nachrüstung von Regenklärbecken mit technischen Regenwasserfiltern
(2023)
Adaptive laser resonators with deformable MOEMS mirrors under closed-loop control are discussed and experimental results are presented. The requirements for deformable mirrors and for closed-loop control systems of these mirrors are analyzed. Several deformable mirrors have been characterized and the results are presented. Currently available membrane mirrors deform under laser load and need further development before they can be used for aberration correction of solid state lasers above some tens of Watts. Nevertheless, the results are encouraging and the requirements are within reach of currently available technology. Finally, we demonstrate an Nd.YVO4-laser with a closed-loop adaptive resonator and more than 6 W of output power. The closed-loop system was able to compensate artificially introduced aberrations from a phase plate.