Graphite formation in cast iron, phase 2

Several types of cast irons are directionally solidified aboard the KC-135 aircraft. Also, control samples are run on Earth for comparison. Some of these samples are unusable because of various mechanical problems; the analysis and the interpretation of results on the samples that are run successfully is discussed

Directional solidification of flake and nodular cast iron during KC-135 low-g maneuvers

Alloys solidified in a low-gravity environment can, due to the elimination of sedimentation and convection, form unique and often desirable microstructures. One method of studying the effects of low-gravity (low-g) on alloy solidification was the use of the NASA KC-135 aircraft flying repetitive low-g maneuvers. Each maneuver gives from 20 to 30 seconds of low-g which is between about 0.1 and 0.001 gravity. A directional solidification furnace was used to study the behavior of off eutectic composition case irons in a low-g environment. The solidification interface of hypereutectic flake and spheroidal graphite case irons was slowly advanced through a rod sample, 5 mm in diameter. Controlled solidification was continued through a number of aircraft parabolas. The known solidification rate of the sample was then correlated with accelerometer data to determine the gravity level during solidification for any location of the sample. The thermal gradient and solidification rate were controlled independently. Samples run on the KC-135 aircraft exhibited bands of coarser graphite or of larger nodules usually corresponding to the regions solidified under low-g. Samples containing high phosphorous (used in order to determine the eutectic cell) exhibited larger eutectic cells in the low-g zone, followed by a band of coarser graphite

Preliminary science report on the directional solidification of hypereutectic cast iron during KC-135 low-G maneuvers

An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft. The system offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation. The directional sodification furnace system was first flown during the September 1982 series of flights. The microstructure of the hypereutectic cast iron sample solidified on one of these flights suggests a low-g effect on graphite morphology. Further experiments are needed to ascertain that this effect is due to low-gravity and to deduce which of the possible mechanisms is responsible for it

SpeckleViz: A Web-based Interactive Activity Network Diagram for AEC

As architectural design and construction projects tend to tackle larger scales and become more complex, the multiple involved disciplines in the Architecture, Engineering and Construction (AEC) sector often need to work globally from different remote locations. This increased complexity impacts digital design up until to fabrication workflows, which become more challenging and discontinuous, as each industry partner involved in the construction of a given project operates on different software environments and needs to access the precise fabrication data of specific design components. Consequently, managing and keeping track of design changes and data flow throughout the whole design process still remains a challenging task. This paper discusses how this particular challenge can be tackled through the development of a web-based interactive Activity Network Diagram (AND)-named SpeckleViz-that continuously maps the data transfers of the design and building processes, enabling the end-user to explore, interact and get a better understanding of the constantly evolving digital design workflow. Through this paper, the authors qualify an "end-user" as an advanced or expert user that performs complex geometry modelling tasks within wider collaborative workflows involving other advanced end-users. SpeckleViz (2020) is an application built upon Speckle (2020), an open-source data platform for the AEC. We illustrate the usefulness of interactive visualization of ANDs in the development of digital design workflows

Advancement of Solidification Processing Technology Through Real Time X-Ray Transmission Microscopy: Sample Preparation

Two types of samples were prepared for the real time X-ray transmission microscopy (XTM) characterization. In the first series directional solidification experiments were carried out to evaluate the critical velocity of engulfment of zirconia particles in the Al and Al-Ni eutectic matrix under ground (l-g) conditions. The particle distribution in the samples was recorded on video before and after the samples were directionally solidified. In the second series samples of the above two type of composites were prepared for directional solidification runs to be carried out on the Advanced Gradient Heating Facility (AGHF) aboard the space shuttle during the LMS mission in June 1996. X-ray microscopy proved to be an invaluable tool for characterizing the particle distribution in the metal matrix samples. This kind of analysis helped in determining accurately the critical velocity of engulfment of ceramic particles by the melt interface in the opaque metal matrix composites. The quality of the cast samples with respect to porosity and instrumented thermocouple sheath breakage or shift could be easily viewed and thus helped in selecting samples for the space shuttle experiments. Summarizing the merits of this technique it can be stated that this technique enabled the use of cast metal matrix composite samples since the particle location was known prior to the experiment

AESTHETICS OF RUDERAL VEGETATION IN THE URBAN AND PERI-URBAN AREAS OF OLTENIA (ROMANIA)

This paper renders the importance of the main ruderal plant associations in unarranged urban and peri-urban areas that bring a high contribution to the aesthetics of these places through their floristic composition.Plants included in this category of vegetation are regarded as "ruderal weeds". The sprawl of the main cities and towns of Oltenia – Craiova, Calafat, Băilești (Dolj County), Rm. Vâlcea, Horezu, Călimăneşti, Drăgăşani, Bălceşti (Vâlcea County), DrobetaTurnu Severin, Orşova (Mehedinţi County), Slatina, Caracal, Corabia (Olt County), Tg. Jiu, Bumbeşti Jiu, Novaci (Gorj County), led to the increase of the surface occupied by this type of vegetation. The preservation or bankruptcy of the factories located at the outskirts of some large cities in Oltenia are other causes of the increase of the surface occupied by this type of vegetation. After analyzing the floristic composition of these surfaces occupied by ruderal vegetation, it was found that there is an appreciable diversity both in terms of number of species and colours of the flowers of these plants. Starting from this last finding, we consider useful to use this type of vegetation for aesthetic purposes.

Latitudinal gradients in butterfly population variability are influenced by landscape heterogeneity

The variability of populations over time is positively associated with their risk of local extinction. Previous work has shown that populations at the high-latitude boundary of species’ ranges show higher inter-annual variability, consistent with increased sensitivity and exposure to adverse climatic conditions. However, patterns of population variability at both high- and low-latitude species range boundaries have not yet been concurrently examined. Here, we assess the inter-annual population variability of 28 butterfly species between 1994 and 2009 at 351 and 18 sites in the United Kingdom and Catalonia, Spain, respectively. Local population variability is examined with respect to the position of the species’ bioclimatic envelopes (i.e. whether the population falls within areas of the ‘core’ climatic suitability or is a climatically ‘marginal’ population), and in relation to local landscape heterogeneity, which may influence these range location – population dynamic relationships. We found that butterfly species consistently show latitudinal gradients in population variability, with increased variability in the more northerly UK. This pattern is even more marked for southerly distributed species with ‘marginal’ climatic suitability in the UK but ‘core’ climatic suitability in Catalonia. In addition, local landscape heterogeneity did influence these range location – population dynamic relationships. Habitat heterogeneity was associated with dampened population dynamics, especially for populations in the UK. Our results suggest that promoting habitat heterogeneity may promote the persistence of populations at high-latitude range boundaries, which may potentially aid northwards expansion under climate warming. We did not find evidence that population variability increases towards southern range boundaries. Sample sizes for this region were low, but there was tentative evidence, in line with previous ecological theory, that local landscape heterogeneity may promote persistence in these retracting low-latitude range boundary populations