253 research outputs found
EVALUATION of AIRBORNE IMAGE VELOCIMETRY APPROACHES USING LOW-COST UAVS in RIVERINE ENVIRONMENTS
No full textTraditional flow velocity measurements in natural environments require contact with the fluid and are usually costly, time-consuming and, sometimes, even dangerous. Particle Image Velocimetry allows the flow velocity field to be remotely characterized from the shift of intensity patterns of sub-image areas in at least two video frames with a known time lag. Recently, Airborne Image Velocimetry has enabled the surface velocity field of large-scale water bodies to be determined by applying Particle Image Velocimetry on videos recorded by cameras mounted on unmanned aerial vehicles. This work presents a comparison of three Airborne Image Velocimetry approaches: BASESURV, Fudaa-LSPIV and RIVeR. For the evaluation, two nadiral videos were acquired with a low-cost quadcopter. The first was recorded under low flow and seeded conditions, the second during a flood event. According to the results obtained, BASESURV is an accurate and complete research oriented approach but it is time-consuming and neither a graphical interface nor documentation are yet provided. Fudaa-LSPIV is a well-developed software package, with a user-friendly graphical interface and good documentation. However it lacks some features and the source code is closed. RIVeR may be suitable for real time monitoring thanks to the rectification of velocity vectors only. Overall, all the codes are found to be effective in performing Airborne Image Velocimetry in riverine environments
Transition in the growth mode of plasmonic bubbles in binary liquids
No full textMulti-component fluids with phase transitions show a plethora of fascinating phenomena with rich physics. Here we report on a transition in the growth mode of plasmonic bubbles in binary liquids. By employing high-speed imaging we reveal that the transition is from slow evaporative to fast convective growth and accompanied by a sudden increase in radius. The transition occurs as the three-phase contact line reaches the spinodal temperature of the more volatile component leading to massive, selective evaporation. This creates a strong solutal Marangoni flow along the bubble which marks the beginning of convective growth. We support this interpretation by simulations. After the transition the bubble starts to oscillate in position and in shape. Though different in magnitude the frequencies of both oscillations follow the same power law [Image: see text] , which is characteristic of bubble shape oscillations, with the surface tension σ as the restoring force and the bubble's added mass as inertia. The transitions and the oscillations both induce a strong motion in the surrounding liquid, opening doors for various applications where local mixing is beneficial
Prospective 7 year follow up imaging study comparing radiography, ultrasonography, and magnetic resonance imaging in rheumatoid arthritis finger joints
No full textObjective: To perform a prospective long term follow up study comparing conventional radiography (CR), ultrasonography ( US), and magnetic resonance imaging (MRI) in the detection of bone erosions and synovitis in rheumatoid arthritis ( RA) finger joints. Methods: The metacarpophalangeal and proximal interphalangeal joints II - V ( 128 joints) of the clinically dominant hand of 16 patients with RA were included. Follow up joint by joint comparisons for erosions and synovitis were made. Results: At baseline, CR detected erosions in 5/128 (4%) of all joints, US in 12/128 (9%), and MRI in 34/ 128 (27%). Seven years later, an increase of joints with erosions was found with CR (26%), US (49%) ( p< 0.001 each), and MRI (32%, NS). In contrast, joint swelling and tenderness assessed by clinical examination were decreased at follow up ( p = 0.2, p< 0.001). A significant reduction in synovitis with US and MRI ( p< 0.001 each) was seen. In CR, 12 patients did not have any erosions at baseline, while in 10/ 12 patients erosions were detected in 25/96 ( 26%) joints after 7 years. US initially detected erosions in 9 joints, of which two of these joints with erosions were seen by CR at follow up. MRI initially found 34 erosions, of which 14 (41%) were then detected by CR. Conclusion: After 7 years, an increase of bone erosions was detected by all imaging modalities. In contrast, clinical improvement and regression of synovitis were seen only with US and MRI. More than one third of erosions previously detected by MRI were seen by CR 7 years later
EFFECTS OF ORGANIZATIONAL CULTURE ON M-GOVERNMENT ADOPTION: A CASE STUDY ON E-PURJEE IN BANGLADESH
No full textWith the rapid growth of mobile technology, m-government services, which are an extension of egovernment, are increasingly becoming an effective alternative. However, similar to other information and communications technology innovations, m-government faces multiple known and unknown challenges at various levels. Although organizational culture has been mentioned in extant literature, this challenge has not been explored in detail, particularly in terms of the dimensions, nature, and overall strength of influence on the innovation itself. This study attempts to fill this void by exploring a particular innovation through an in-depth study in Bangladesh. The framework by Detert et al. (2000) is used as a guide to investigate the various dimensions of organizational culture and characterize the context under study. The paper highlights strong influence of organizational culture and underlines the importance of delving deeper into this influence at every step of such innovation in a developing country, from planning, design, and implementation
Second harmonic generation in SiO2 sol-gel films functionalized with Ethyl-[4-(4-nitro-phenylazo)-phenyl]-(2-oxiranylmethoxy-ethyl)-amine (ENPMA) molecules
No full textHigh concentrations of Ethyl-[4-(4-nitro-phenylazo)-phenyl]-(2-oxiranylmethoxy-ethyl)-amine (ENPMA) chromophores were linked covalently to two different kinds of SiO2 matrices prepared by the sol–gel method. The matrices differed in their reticulation level, determined by the organometallic precursor used during the synthesis. The materials were deposited as films by spin-coating. The chromophores in the films were oriented in a non-centrosymmetric way by a modified Corona poling set-up, and the nonresonant second order non-linear optical coefficient d33(0) of the films was determined by means of the Maker fringe
technique. It was found that there is an optimum concentration of chromophores for attaining the highest d33(0) value in these materials. Their maximum d33(0) value was found in the films with the least reticulated matrix, that value was equal to 5.2±0.5 pm/V. Besides, the d33(0) value was more stable in time in the less reticulated materials
Methoden zur Zuverlässigkeitsqualifizierung neuer Technologien in der Aufbau- und Verbindungstechnik
No full textBei der heutigen Geschwindigkeit der Einführung neuer Elektronikprodukte müssen Entwicklungszeit von wenigen Monaten bis Jahren realisiert werden. Dies ist auch aus ökonomischen Gründen zwingend notwendig, weil die Produkte je nach Anwendung nur kurzzeitig unverändert am Markt bleiben, bei PC etwa nur einige Monate und bei Fahrzeugelektronik wenige Jahre. Eine der wesentlichen Anforderungen an moderne Elektronikhardware ist die Zuverlässigkeit. Bei den meisten Produkten ist die Reparatur in der Regel ausgeschlossen. Die Aufbau- und Verbindungstechnik repräsentiert eine Sammeltechnologie, die den Halbleiter in ein Bauelement, Modul oder eine Baugruppe integriert. Ein sehr großer Teil der Aktivitäten zur Sicherstellung der Zuverlässigkeit wird daher auf die AVT konzentriert. Die gängige Vorgehensweise ist dabei Spezifikation, Konzepterstellung, Auslegung, Musterbau, Prüfung und ggf. Iteration zur Optimierung. Es ist klar, dass bei einer spezifizierten Lebensdauer von beispielsweise 5.000 h nur dann eine kürzere Entwicklungszeit als ein halbes Jahr unmöglich wird, wenn besondere Maßnahmen zur Verminderung des Aufwandes und zur Verkürzung von Prüfzeiten getroffen werden. Die Fragestellung, wie man die Zuverlässigkeit neuer Aufbau- und Verbindungstechniken effizient sicherstellt, wurde seit einiger Zeit öfters an den Ausschuss heran getragen. Das Problem wird umso brennender, wenn es sich um grundsätzlich neue Technologien handelt, für die noch kaum Erfahrung existiert. Die Betrachtung einiger ?neuer? Technologien der AVT wie Chip-Scale-Package, Low- Temperature-Cofired-Ceramics oder Direct-Copper-Bonding zeigt, dass in der Regel vom Ende des Forschungsstadiums bis zu einer signifikanten Marktdurchdringung ein Zeitraum von einem Jahrzehnt vergeht
Significance of B-mode, power Doppler- and echo-intensifier sonography in RA patients under anti-TNF alpha treatment
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Untersuchungen zur Optimierung von elektrischen Schaltungsträgern auf der Basis von Keramik-Metall-Verbunden
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