A fast method for mobile in-situ monitoring of optical properties in aquatic environments

In summary, this dissertation presents a fundamental sensor development according to newly formulated sampling theorem (Object Specific Exposure - OSE) from an ocean engineering perspective. It provides a fast method based on a service-oriented optical sensor system that allows reliable statements regarding the state of aquatic (eco-) systems (turbidity and dissolved organic carbon) with feasible sensor effort during the field measurement. The technological approach presented in this thesis helps to increase the informative value of sensor data while reducing the effort for the user.Zusammenfassend stellt diese Dissertation eine grundlegende Sensorentwicklung nach einem neu formulierten Monitoring-Theorem (Object Specific Exposure - OSE) aus meerestechnischer Sicht dar. Vorgestellt wird eine Methode, die auf Basis eines serviceorientierten optischen Sensorsystems Aussagen über den Zustand von aquatischen (Öko-) Systemen (Trübung und Gehalt gelöster organischer Verbindungen) mit geringem methodischen Sensoraufwand im Feld ermöglicht

Effect of stenosis geometry on the Doppler-catheter gradient relation in vitro: A manifestation of pressure recovery

AbstractObjectives. This study investigated the effect of stenosis geometry on the Doppler-catheter gradient relation.Background. Although gradient estimation by Doppler ultrasound has been shown to be accurate in various clinical and in vitro settings, there have also been reports of substantial discrepancies between Doppler and catheter gradients. These conflicting results may be due to differences in geometry and hemodynamic characteristics of flow obstructions.Methods. Stenoses of various geometry were simultaneously studied with continuous wave Doppler and catheter technique in a well controlled pulsatile flow model.Results. Doppler and catheter gradients correlated very well regardless of stenosis geometry and site of distal catheter measurement (r = 0.98 to 0.99, SEE = 1.8 to 5.3 mm Hg). When the catheter was pulled back through the stenosis, the highest gradients were found in or close to the stenosis. When these catheter gradients were compared with Doppler gradients, the agreement between the two techniques was excellent regardless of stenosis geometry (slope 0.97; mean difference 0.6 ± 2.0 mm Hg). However, when distal pressures were measured 10 cm downstream from the stenotic segment, the slope of the regression line, and therefore the agreement between Doppler and catheter gradients, differed for the different stenosis types (slopes from 0.98 to 1.69). In stenoses with abrupt narrowing and abrupt expansion, agreement was acceptable. Doppler gradients were only slightly greater than catheter gradients (mean difference 4.5 ± 5.2 mm Hg). In stenoses with a gradually tapering inlet and outlet, the Doppler-catheter gradient relation was dependent on the outflow angle. Good agreement was found for an angle of 60 ° (mean difference 0.6 ± 1.8 mm Hg). In stenoses with a 40 ° outflow angle, Doppler gradients exceeded the catheter gradients by 13% on average; for stenoses with a 20 ° outflow angle, Doppler gradients exceeded catheter gradients by 46 ± 11.4%, with differences as great as 65 mm Hg. These results were identical for stenoses gradually tapering outward to the distal tubing diameter and those with abrupt expansion after 2 cm of gradual expansion. The results were also not affected by changing the inflow angle from 20 ° to 60 °. However, an abrupt narrowing instead of a tapering inlet significantly altered the Doppler-catheter gradient relation (p < 0.001); Doppler gradients exceeded the catheter gradients by 34 ± 10% for this stenosis type.Conclusions. Doppler gradients accurately reflect the highest gradients across flow obstructions that occur in the vena contracta. However, these gradients may be significantly greater than catheter gradients that are measured farther downstream, as is usually the case in clinical catheterization studies. These discrepancies are due to pressure recovery. The magnitude of pressure recovery is highly dependent on the stenosis geometry, which therefore significantly affects the Doppler-catheter gradient relation. It is the outflow geometry that predominantly influences this relation, but the shape of the inlet may affect the results as well. Although pressure recovery occurs even in stenoses with abrupt narrowing and abrupt expansion, the phenomenon is most likely to become clinically relevant in stenoses with a gradually tapering inlet and outlet with an outflow angle ≥20 °

Radiometric density measurement for silage compaction in bunker silos

Certain minimum densities should be targeted when storing silage in bunker silos.  However, farmers lack facilities to measure the actual density and then steer the compaction passes.  This study was aimed at developing a measuring device for onsite density measurement.  The basis of the measuring device was a source of caesium radiation with an activity of    37 MBq and a sodium iodide scintillation detector.  The measuring device used the backscattering method.  The source and detector were located in a measuring wheel that was connected with the tractor via the rear three-point linkage.  During measuring passes on bunker silos both the density increase in the case of several crossings and the elastic recovery of the material could be seen clearly.  In connection with satellite-based position determination, the silo surface can be mapped according to density.  As a result of the random decay of the caesium, the error in density measurement was only ±4% at   600 kg m-3.   Keywords: silage compaction, bunker silo, silage density, radiometric measuring devic

ОБОБЩЕНИЕ РЕЗУЛЬТАТОВ ИССЛЕДОВАНИЙ МАГНИТНОЙ ВОСПРИИМЧИВОСТИ СОСТАВЛЯЮЩИХ БАЗАЛЬТОВОГО СЫРЬЯ

Объектом исследований являлись базальты Волыни, поскольку здесь ве-дется их интенсивная карьерная разработка. Внимание исследователей привле-кает уникальный состав базальтов и возможность их более рационального ис-пользования. В настоящее время базальт используется в основном как строи-тельный материал в виде щебня, в небольших количествах – для производства теплоизоляционной ваты. Однако исследования, выполненные геологами, уче-ными различных организаций, показали [1-4], что базальт является ценным ми-неральным сырьем и требует комплексной переработки для извлечения полез-ных компонентов, содержащихся в количествах, представляющих промышлен-ный интерес, и технологическую возможность их извлечения. Наличие приме-сей в массиве базальта в виде лавобрекчий и туфов не снижает актуальности и ценности идеи комплексной переработки, поскольку эти ингредиенты в своем составе содержат те же полезные компоненты, что и базальт. Основными из них являются самородная медь, железо и титан [4]. Более глубокие исследования показали, что в них содержатся окислы меди, редкие и ценные металлы, извле-чение которых требует более тонких технологий

The influence of bicuspid aortic valves on the dynamic pressure distribution in the ascending aorta: a porcine ex vivo model †

OBJECTIVES The aim of the study was to simulate the effect of different bicuspid aortic valve configurations on the dynamic pressure distribution in the ascending aorta. METHODS Aortic specimens were harvested from adult domestic pigs. In Group 1, bicuspidalization was created by a running suture between the left and the right coronary leaflets (n = 6) and in Group 2 by a running suture between the left and the non-coronary leaflets (n = 6). Eleven tricuspid specimens served as controls. Two intraluminal pressure catheters were positioned at the concavity and the convexity of the ascending aorta. The specimens were connected to a mock circulation (heart rate: 60 bpm, target pressure: 95 mmHg). A comparison of the different conditions was also done in a numerical simulation. RESULTS At a distal mean aortic pressure of 94 ± 10 mmHg, a mean flow rate of 5.2 ± 0.3 l/min was achieved. The difference of maximal dynamic pressure values (which occurred in systole) between locations at the convexity and the concavity was 7.8 ± 2.9 mmHg for the bicuspid and 1.0 ± 0.9 mmHg for the tricuspid specimens (P < 0.001). The numerical simulation revealed an even higher pressure difference between convexity and concavity for bicuspid formation. CONCLUSIONS In this hydrodynamic mock circulation model, we were able to demonstrate that bicuspid aortic valves are associated with significant pressure differences in different locations within the ascending aorta compared with tricuspid aortic valves. These altered pressure distributions and flow patterns may further add to the understanding of aneurismal development in patients with bicuspid aortic valves and might serve to anticipate adverse aortic events due to a better knowledge of the underlying mechanism

On the Incorporation of Obstacles in a Fluid Flow Problem Using a Navier-Stokes-Brinkman Penalization Approach

Simulating the interaction of fluids with immersed moving solids is playing an important role for gaining a better quantitative understanding of how fluid dynamics is altered by the presence of obstacles and which forces are exerted on the solids by the moving fluid. Such problems appear in various contexts, ranging from numerous technical applications such as turbines to medical problems such as the regulation of hemodyamics by valves. Typically, the numerical treatment of such problems is posed within a fluid structure interaction (FSI) framework. General FSI models are able to capture bidirectional interactions, but are challenging to solve and computationally expensive. Simplified methods offer a possible remedy by achieving better computational efficiency to broaden the scope to demanding application problems with focus on understanding the effect of solids on altering fluid dynamics. In this study we report on the development of a novel method for such applications. In our method rigid moving obstacles are incorporated in a fluid dynamics context using concepts from porous media theory. Based on the Navier-Stokes-Brinkman equations which augments the Navier-Stokes equation with a Darcy drag term our method represents solid obstacles as time-varying regions containing a porous medium of vanishing permeability. Numerical stabilization and turbulence modeling is dealt with by using a residual based variational multiscale formulation. The key advantages of our approach -- computational efficiency and ease of implementation -- are demonstrated by solving a standard benchmark problem of a rotating blood pump posed by the Food and Drug Administration Agency (FDA). Validity is demonstrated by conducting a mesh convergence study and by comparison against the extensive set of experimental data provided for this benchmark

PlenoptiSign: An optical design tool for plenoptic imaging

© 2019 The Authors. Published by Elsevier. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1016/j.softx.2019.100259© 2019 The Authors Plenoptic imaging enables a light-field to be captured by a single monocular objective lens and an array of micro lenses attached to an image sensor. Metric distances of the light-field's depth planes remain unapparent prior to acquisition. Recent research showed that sampled depth locations rely on the parameters of the system's optical components. This paper presents PlenoptiSign, which implements these findings as a Python software package to help assist in an experimental or prototyping stage of a plenoptic system.Published versio