An improved approach for automatic process plan generation of complex borings

The authors are grateful for funding provided to this project by the French Ministry of Industry, Dassault Aviation, Dassault Systemes, and F. Vernadat for his review and recommendations.The research concerns automated generation of process plans using knowledge formalization and capitalization. Tools allowing designers to deal with issues and specifications of the machining domain are taken into account. The main objective of the current work is to prevent designers from designing solutions that would be expensive and difficult to machine. Among all available solutions to achieve this goal, two are distinguished: the generative approach and the analogy approach. The generative approach is more adapted to generate the machining plans of parts composed of numerous boring operations in interaction. However, generative systems have two major problems: proposed solutions are often too numerous and are only geometrically but not technologically relevant. In order to overcome these drawbacks, two new concepts of feature and three control algorithms are developed. The paper presents the two new features: the Machining Enabled Geometrical Feature (MEGF) and the Machinable Features (MbF). This development is the result of the separation of the geometrical and the technological data contained in one machining feature. The second objective of the paper is to improve the current Process Ascending Generation (PAG) system with control algorithms in order to limit the combinatorial explosion and disable the generation of unusable or not machinable solutions

An improved approach for automatic process plan generation of complex borings

The authors are grateful for funding provided to this project by the French Ministry of Industry, Dassault Aviation, Dassault Systemes, and F. Vernadat for his review and recommendations.The research concerns automated generation of process plans using knowledge formalization and capitalization. Tools allowing designers to deal with issues and specifications of the machining domain are taken into account. The main objective of the current work is to prevent designers from designing solutions that would be expensive and difficult to machine. Among all available solutions to achieve this goal, two are distinguished: the generative approach and the analogy approach. The generative approach is more adapted to generate the machining plans of parts composed of numerous boring operations in interaction. However, generative systems have two major problems: proposed solutions are often too numerous and are only geometrically but not technologically relevant. In order to overcome these drawbacks, two new concepts of feature and three control algorithms are developed. The paper presents the two new features: the Machining Enabled Geometrical Feature (MEGF) and the Machinable Features (MbF). This development is the result of the separation of the geometrical and the technological data contained in one machining feature. The second objective of the paper is to improve the current Process Ascending Generation (PAG) system with control algorithms in order to limit the combinatorial explosion and disable the generation of unusable or not machinable solutions

Development of Soil Compressibility Prediction Models

The magnitude of the overall settlement depends on several variables such as the Compression Index, Cc, and Recompression Index, Cr, which are determined by a consolidation test; however, the test is time consuming and labor intensive. Correlations have been developed to approximate these compressibility indexes. In this study, a data driven approach has been employed in order to estimate Cc and Cr. Support Vector Machines classification is used to determine the number of distinct models to be developed. The statistical models are built through a forward selection stepwise regression procedure. Ten variables were used, including the moisture content (w), initial void ratio (eo), dry unit weight (γdry), wet unit weight (γwet), automatic hammer SPT blow count (N), overburden stress (σ), fines content (-200), liquid limit (LL), plasticity index (PI), and specific gravity (Gs). The results confirm the need for separate models for three out of four soil types, these being Coarse Grained, Fine Grained, and Organic Peat. The models for each classification have varying degrees of accuracy. The correlations were tested through a series of field tests, settlement analysis, and comparison to known site settlement. The first analysis incorporates developed correlations for Cr, and the second utilizes measured Cc and Cr for each soil layer. The predicted settlements from these two analyses were compared to the measured settlement taken in close proximity. Upon conclusion of the analyses, the results indicate that settlement predictions applying a rule of thumb equating Cc to Cr, accounting for elastic settlement, and using a conventional influence zone of settlement, compares more favorably to measured settlement than that of predictions using measured compressibility index(s). Accuracy of settlement predictions is contingent on a thorough field investigation

Impact of Geographical Information Systems on Geotechnical Engineering

Over the last four decades Geographical Information Systems (GIS) have emerged as the predominant medium for graphic representation of geospatial data, including geotechnical, geologic and hydrologic information routinely used by geotechnical and geoenvironmental engineers. GIS allow unlimited forms of spatial data to be co-mingled, weighted and sorted with any number of physical or environmental factors. These data can also be combined with weighted political and aesthetic values to create hybrid graphic products capable of swaying public perceptions and decision making. The downside of some GIS products is that their apparent efficacy and crispness can also be deceptive, if data of unparalleled reliability is absorbed in the mix. Disparities in data age and quality are common when compiling geotechnical and geoenvironmental data. Despite these inherent shortcomings, GIS will continue to grow and evolve as the principal technical communication medium over the foreseeable future and engineers will be forced to prepare their work products in GIS formats which can be widely disseminated through the world wide web. This paper presents the historical evolution of GIS technologies as it relates to the impact in geotechnical engineering, concluding with four case histories on the application of this emerging technology

The Deep Space Network

The functions and facilities of the Deep Space Network, its supporting research and technology and network operations are discussed

Comparative sedimentology and paleoecology of fossil giant oyster beds in some tertiary strata of New Zealand and Argentina

Shell concentrations are useful indicators of relative sea-level changes, systems tracts, and depositional sequence and boundary surfaces. Shellbeds can equally act as archives of paleoenvironmental information and aid in the reconstruction of past environmental and ecological conditions. These considerations are applied in this study to occurrences of giant oyster reefs and shellbeds in Tertiary sequences in North Island, New Zealand, and in Patagonia, southern Argentina. Large recliner morphotype Flemingostreini Stenzel oysters are common in the Oligocene Orahiri Limestone in the vicinity of Waitomo, New Zealand. The oysters occur in tabular beds typically 0.5-2 m, but up to 9 m thick within highly indurated biomicritic limestone. Individual valves reach 15 cm in length, 10 cm in width and 2.5 to 5 cm in thickness. The occurences at Waitomo are characteristic of multi-event shellbeds and can be interpreted as onlap (transgressive lag) and backlap shellbeds within a transgressive systems tract. Shell delta18O (-2.1 to 1.4 per mille) and delta13C (0.4 and 2.5 per mille) values, and minimal seasonal isotopic ranges with little variability, confirm that these oysters lived in a fully marine environment. The environment of Oligocene Flemingstreini Stenzel was probably similar to modern Ostrea chilensis from Foveaux Strait off southern New Zealand, living on coarse shelly and gravelly tide swept substrates in 18-40 m water depth, under normal marine salinity conditions and temperatures around 13oC, forming in situ biostromes of haphazardly packed oyster shells. Specimens of Ostrea patagonica in the Late Miocene Puerto Madryn Formation, Pen nsula Vald s, Patagonia, are held in a weakly calcareous fine sand host. They reach 20 cm in length, 5 cm thick and weigh as much as 3 kg. The reef has a lens (or bioherm) geometry and is composed of articulated, well preserved oysters set in a fine sand matrix. The reef is interpreted as a downlap shellbed within a highstand systems tract. Oyster shell delta18O (-4.4 to -3.2 per mille) and delta13C (-2.0 to -3.2 per mille) values are low and show large seasonal isotopic ranges, with a large amount of variability, collectively supporting a marginal marine setting receiving extensive freshwater input and mixing. The environment of these oysters is comparable with modern Crassostrea gigas reefs at San Blas, Patagonia. Ostrea patagonica occupied a low energy intertidal zone in water depths of only 1-2 m. Temperatures ranged from 20degreesC (summer maximum) to 8degreesC (winter minimum). The oysters were not cemented firmly to the substrate, but reclined on the muddy sediment and formed an in situ bioherm of loosely packed oysters, with the living animals concentrated over time to the outside of the accumulation. The Pliocene Wilkies Shellbed in the Wanganui Basin, New Zealand, comprises oyster accumulations up to 15 m thick involving the extinct oyster Crassostrea ingens. Individuals are up to 30 cm long, 7 cm thick and weigh as much as 2 kg. The shellbed consists of a lower onlap shellbed (transgressive lag) and an overlying backlap shellbed (biostrome). The widespread shell delta18O (-3.0 to 3.0 per mille) and delta13C (-2.6 to 1.8 per mille) isotopic values support a range of marginal marine to marine environmental conditions. The lower onlap shellbed had estuarine influence, while the upper part had affinities with a nearshore (less than 40 m) marine setting of more normal salinity. As the thick backlap shellbed migrated shoreward a depth was maintained in which Crassostrea could live in situ within a weakly calcareous very fine muddy sand in favourable conditions of low turbidity and sedimentation. All species of fossil oysters in this study are easily distinguished by the large size and thickness of their valves. The 'reefs' formed by these oysters provided hard substrata for a diverse community of encrusting and boring organisms which includes the likes of Gastrochaenolites (bivalve), Maeandropolydora (polychaete), Clionolithes (boring algae), Entobia (sponge), Leptichnus (bryozoan) and Radulichnus (gastropod). These communities are comparable to those seen on extant oyster reefs. They can thus be termed autogenic ecosystem engineers. Non-random distribution of euendoliths and epiliths on oyster valves may be accounted for by different survival adaptations of larvae. Shell morphotypes and exterior architectures are inferred to have prompted active rugophilic (groove-seeking), geophobic (anti-gravity) and rheophilic (current-seeking) behaviour of larvae, which enhanced their survival rate. Preference for the external surface of shells suggests that traces were created during the life time of the oysters, while most internal traces are post-mortem features

Research reports: 1990 NASA/ASEE Summer Faculty Fellowship Program

Reports on the research projects performed under the NASA/ASEE Summer Faculty Fellowship Program are presented. The program was conducted by The University of Alabama and MSFC during the period from June 4, 1990 through August 10, 1990. Some of the topics covered include: (1) Space Shuttles; (2) Space Station Freedom; (3) information systems; (4) materials and processes; (4) Space Shuttle main engine; (5) aerospace sciences; (6) mathematical models; (7) mission operations; (8) systems analysis and integration; (9) systems control; (10) structures and dynamics; (11) aerospace safety; and (12) remote sensin

Studying Complex Aquifer Systems from Large-Scale Stratigraphy Development to Local Aquifer Storage and Recovery

Hydrostratigraphy model is an essential component of building valid groundwater models. Many challenges are associated with constructing hydrostratigraphy models which include geological complexities such as faults, domes, and angular unconformities. Developing a method with an emphasis on capturing big data to thoroughly inform large-scale models is one of the challenges addressed in the first part of this study. The method is predicated upon discretization of the study domain into tiles based on the geological dip direction and faults. The application of the method in the state of Louisiana with the utilization of more than 114000 well logs demonstrates promising results including identification of hydrostratigraphic characteristics for different aquifers, connections between the Mississippi River and the Red River and their alluviums, connections between state\u27s surface waters and aquifers, and identification of recharge zones. The Louisiana model also demonstrated two different sand patterns in southeast Louisiana which might have been caused by two depositional environments. Employment of the method in a groundwater flow modeling framework to build a flow model for the Chicot aquifer system in southwest Louisiana revealed the complexity of the aquifer system that contains highly interconnected aquifer sands. The groundwater flow analysis of the Chicot aquifer is of great importance because it is the most heavily pumped aquifer in the state as a part of the Coastal Lowland Aquifer System. The modeling results show that the storage loss due to groundwater pumping is offset by inflows from surficial recharge, rivers, and boundaries. The two large cones of depression created by the agricultural pumping in the east and by the industrial pumping in the west represent the key feature in the Chicot aquifer system. As the final goal of this study, an aquifer storage and recovery operation in south of the Chicot aquifer was studied. The focus of this part was on optimal scheduling of an aquifer storage and recovery (ASR) operation while addressing parameter uncertainty for one cycle where an injection season is followed by a pumping season. This end was achieved via utilization of a supervised learning method for surrogated modeling and use of an evolutionary optimization method. The results indicate that artificial neural network (ANN) is a promising tool for evaluation of ASR efficiency. The hydraulic conductivity and longitudinal dispersivity were found to be the most significant parameters which affect ASR