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1

Non intrusive density measurements in gravity currents interacting with an obstacle

Adduce Claudia, Maggi Maria Rita, De Falco Maria Chiara

Acta Geophysica

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2022

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Vol. 70, no 5

2499--2510

EN

Gravity currents are flows produced by a density difference between two fluids. Non-intrusive density measurements, based on image analysis, are employed to measure the instantaneous width averaged density fields of lock-release gravity currents. The developed technique uses dye concentration as a tracer. For each pixel of the acquired images, a calibration procedure is applied to relate the concentration of dye, uniformly distributed in the experimental tank, and the greyscale. Two calibration techniques with nine-image and two-image calibration curves, respectively, are employed to evaluate the instantaneous density fields of a gravity current with and without a bottom obstacle. The two different calibration curves affect the measurement results, i.e. instantaneous density fields, front propagation, current area and mixing. The image analysis using a nine-image calibration curve is found to give better results compared to the technique with a two-image calibration curve. The analysis performed shows how the image analysis based on a nine-image calibration curve is a more suitable technique for the study of the gravity currents dynamics and the associated mixing, which are strongly affected by the presence of a bottom obstacle.

2

Determination of bubble size distribution in a laboratory mechanical flotation cell by a laser diffraction technique

Mazahernasab R., Ahmadi R.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

690--702

EN

In this study, a laser diffraction technique (LDT) was used to measure size distribution of bubbles generated in a two-phase system in a laboratory mechanical flotation cell. In LDT, a laser light beam passed through the bubbles inside the measurement cell and the scattered light was recorded by detectors. In order to show the effectiveness of LDT, an image analysis technique (IAT) was applied in parallel to measure the size of bubbles. To determine the bubble size by IAT, around 200 images were taken in each test. In addition, the important operating parameters of the mechanical flotation cell affecting the bubble size distribution, including the impeller speed, aeration rate and frother concentration, were investigated. The response parameter in this study was Db(50) which represent the size of bubble at which there is 50% of the distribution. The results of this study showed that the LDT and IAT techniques were in a good agreement when Db(50) was in the range of -800+400 μm and there was a discrepancy for Db(50) in the range of -400+100 μm. Furthermore, Db(50) decreased from 727 to 284 μm when impeller speed increased from 700 to 1200 rpm. Additionally, an increase in the aeration rate from 1 dm3/min to 2.5 dm3/min led to a rise in Db(50) from 418 to 456 μm. Finally, increasing the frother concentration from 10 to 60 ppm reduced the Db(50) from 704 to 387 μm.

3

Wpływ obciążenia ładunkiem zanieczyszczeń na morfologię kłaczków osadu czynnego

Andrzejczak O., Liwarska-Bizukojc E.

Gaz, Woda i Technika Sanitarna

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2014

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Nr 12

480--484

PL

W pracy przedstawiono badania obejmujące wpływ obciążenia osadu ładunkiem zanieczyszczeń na parametry morfologiczne kłaczków osadu czynnego, takie jak pole powierzchni rzutu, średnica, obwód, kolistość oraz wypukłość kłaczków osadu czynnego jak również na udział bakterii nitkowatych w osadzie czynnym. W celu analizy osadu czynnego wykorzystano techniki cyfrowej analizy obrazu. W badanym osadzie stwierdzono obecność bakterii nitkowatych, których udział określano przy pomocy takich parametrów jak sumaryczna długość nitek na obraz, sumaryczna długość nitek na objętość oraz stosunek sumarycznego pola powierzchni nitek do sumarycznego pola powierzchni agregatów na obraz. Nie stwierdzono jednoznacznej zależności pomiędzy ilością bakterii nitkowatych a indeksem objętościowym w badanym zakresie obciążeń.

EN

The influence of organic loading rate on morphological parameters of the activated sludge flocs and the contribution of filamentous bacteria was studied. Morphological parameters such as area, diameter, perimeter, circularity and convexity were measured. The share of filamentous bacteria was measured using such parameters as total length of filamentous per image, total length of filamentous per volume, the ratio between medium area of filamentous and medium area of aggregates per image. Relationship between sludge volume index and the amount of filamentous bacteria was not found for the activated sludge loading tested.

4

Diagnostyka betonu na podstawie badania struktury

Brandt A. M.

Przegląd Budowlany

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2011

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R. 82, nr 10

53-61

PL

Diagnostyka może dotyczyć różnych dziedzin, od biologicznego stanu zdrowia przez sytuację ekonomiczną lub społeczną aż do zagadnień technicznych, np. stanu konstrukcji czy maszyny. Przyjęto rozumieć znaczenie tego słowa jako identyfikację objawów i obecnego stanu przedmiotu zainteresowania oraz poznanie przyczyn i skutków tego stanu. W diagnostyce betonu można odróżniać różne przyczyny wad lub uszkodzeń: pochodzenia mechanicznego, np. w wyniku nadmiernego obciążenia, także lokalne skutki działań chemicznych (korozja, reakcja alkalia-kruszywo i in.) lub fizycznych, np. zmian termicznych, cykli zamrażania. Niektóre uszkodzenia mają źródło w procesach zachodzących w zaczynie cementowym lub w warstwie kontaktowej, a inne wynikają z warunków użytkowania konstrukcji. Diagnoza może obejmować także przewidywanie zakresu i rodzaju oddziaływania stwierdzonych defektów na dalsze zmiany właściwości betonu.

EN

The structure of concrete is analyzed from the view point of a diagnosis that should cover identification and estimation of possible damages and failures. High quality of concrete is essential in order to ensure adequate durability of a concrete structure. Various elements of the structure are described and the importance of its quantitative analysis is underlined. In a concrete the aggregate grains, pores, fibres, cracks and microcracks may be distinguished, i.e. their percentage volume and density, distribution and direction, origin and quality, as well as other features may be defined. For such aim usually the computer image analysis is applied. On the basis of a thorough structural analysis of the concrete it is possible to determine its quality, to check applicability of designed composition and to verify used components.