A Software Package for Design and Manufacture of Prosthetic Sockets for Transtibial Amputees

A software package, written in Pascal, whkh automates the shape management process associated with fitting prosthetic sockets to transtibial (below-knee) amputees, is described. The system allows an operator to apply global and piecewise transformations, based upon clinkal measurements, to a primitive socket database. These transformations yield a modified socket database which defines the surface shape of a positive socket mold over which an amputee's prosthetic socket is formed. The mold is replicated using a computer numerkally controled milling machine, with the final socket being formed over this mold by a specialized vacuum former. Preliminary clinical trials indkate that this automated approach to shape management yields comfortable prostheses, with savings in time and cost over the traditional methods of prosthesis manufacture.     

Evaporated Te on CdTe: A vacuum-compatible approach to making back contact to CdTe solar cell devices

A commonly used process for forming low-resistance contacts to thin-film p-type CdTe involves the formation of a Te layer by etching the CdTe film in a concentrated mixture of nitric and phosphoric acids. The authors compare evaporated Te back contacts with ‘control’ back contacts formed by the usual etching process, and demonstrate that evaporating Te onto a CdTe thin film is a viable process for forming a low-resistance contact. The best efficiency achieved for a CdTe solar cell made with an evaporated Te back contact is 12.1%, whereas the efficiency of the device made with the control back contact was 11.9%. The evaporation process offers numerous advantages over acid etching, most notably vacuum compatibility amenable to large-scale production of CdTe solar cell modules.     

Computer analysis of a polymer coating exposed to field weather conditions

A heat and moisture transfer model was used to study weathering of polymeric materials, such as paint, asphalt, sealants, plastics, textiles, and polymeric composites. Three damage indices, related to temperature changes, humidity changes, and time of wetness, respectively, were introduced to quantify adverse effects of climate. The variation of these indices was investigated for a hot and humid climate (Miami, FL) and a hot and dry climate (Phoenix, AZ). In addition, the relative effects of solar radiation, surface wetting by rain and dew condensation, and variations in outdoor temperature and relative humidity on the three damage indices were investigated. 100 Bureau Dr., Stop 8621, Gaithersburg, MD 20899-8621.     

Extraction/conversion of geometric dimensions and tolerances for machining features

It is important for a feature-based system to preserve feature integrity during feature operation, especially when feature interaction occurs. The paper presents a feature conversion approach to convert design features used in a design model into machining features for the downstream applications. This process includes both form features (geometric information) and non-geometric features conversion. Most researchers have concentrated on geometric information extraction and conversion without tackling the important problem of non-geometric feature information. This paper focuses on the extraction and conversion of feature geometric dimensions and tolerances (GD&T) for downstream machining application.The main barrier to the integration of a feature-based CAD/CAPP/CAM system – feature interaction – is discussed in this paper, which alters design features in their geometries and non-geometric information. How to identify and validate these feature dimensions and tolerances is one of the key issues in feature interaction conversion. The development of robust methodologies for preserving feature integrity for use in process planning application is the main thrust of the work reported in this paper.     

Transparent,methacrylate-based polymer networks with controlled crosslinker ductility

A series of transparent methacrylate-based crosslinked polymer networks are prepared in which the crosslinker length is controlled as a means to investigate the effects of network ductility on mechanical and ballistic properties. In each network the optical clarity of pure poly(methyl methacrylate) (PMMA) is retained, as well as a low value of haze. Both the glass transition temperature (T_g) and the tensile modulus of the networks are highly tunable, with network values both above and well below that of pure PMMA or the pure crosslinker network. The ballistic performance is likewise affected, with performance values of up to 400% greater than neat PMMA. We examine the effects of the crosslinker molecular weight on the impact performance, finding that, in these systems, the molecular weight between crosslinks is not a driving factor for the impact performance, and this may broadly translate to polymer networks in general. We find that improvements in ballistic performance can be realized at low molecular weight between crosslinks, provided the crosslinking agent is of sufficient ductility.     

Developing habitat associations for fishes in Lake Winnipeg by linking large scale bathymetric and substrate data with fish telemetry detections

Understanding relationships between freshwater fishes and habitat is critical for effective fisheries and habitat management. Habitat suitability indices (HSI) are commonly used to describe fish–habitat associations in rivers and other freshwater ecosystems. When applied to large lakes however, standard sampling procedures are inadequate because of larger sampling areas and an increased risk of fish collection bias through one-time observations. Here, we use lake bathymetry, substrate, and multiple fish telemetry detections collected from a systematically deployed receiver grid to develop HSI for four fish species (lake sturgeon, freshwater drum, common carp, and walleye) in Lake Winnipeg. Seasonal variations in habitat use based on water depth and substrate were observed in three of four species. Lake sturgeon remained in shallow locations with predominantly gravel substrate near the mouth of the Winnipeg River regardless of season. Freshwater drum persisted over fine substrate in both summer and winter but had a broader depth range in the summer compared to winter. Common carp shifted from mid-range depths and silt substrate in the summer to shallow depths and gravel substrate in the winter. Walleye showed an unchanging association to fine substrate but expanded from primarily mid-range depths in the summer to include shallower depths in the winter. These findings show how multiple telemetry detections per fish can be combined with hydroacoustic data to provide informative habitat associations for fishes in a large lacustrine ecosystem.     

Conjunctive Management of Large-Scale Pressurized Water Distribution and Groundwater Systems in Semi-Arid Area with Parallel Genetic Algorithm

This study develops a production well management model for the conjunctive management of water resources in semi-arid areas. The management model integrates a large-scale pressurized water distribution system and a three-dimensional groundwater model under an optimization framework. The well pump operations optimization problem is formulated as a Boolean integer nonlinear programming (BINLP) problem to optimize the periodic 24-h pump on/off operations over a 1-week operation horizon. The management model considers multiple objectives and is solved by a parallel genetic algorithm (PGA) to overcome the difficulty of solving the BINLP problem. The PGA significantly reduces computation time for a case study in Chandler, Arizona. The Chandler water distribution model is built based on EPANET, and the Chandler three-dimension groundwater model is developed using MODFLOW. The high performance computing (HPC) of the genetic algorithm makes it possible to obtain 24-h real-time operations in the 7-day forecast model. The tank reliability, resilience, and vulnerability (R-R-V) are evaluated to infer the system reliability. The Pareto curve provides compromise solutions between the two competing objectives of energy reduction and pressure violation reduction.     

Water Quality Modeling of Lake Michigan and Consideration of the Anomalous Ice Cover of 1976–1977

An intensive survey of water quality parameters was conducted on Lake Michigan during 1976 and 1977. A dynamic phytoplankton simulation model (MICH1) was developed to investigate the observed field data and to use in forecasting lake responses to various phosphorus loading scenarios. The 1977 data indicated that the southern basin of Lake Michigan lost up to 3 μg P/ L compared to concentrations observed in 1976. In an attempt to simulate this rapid depletion of phosphorus, MICH1 required an implicit representation of suspected effects of an extensive ice cover observed during the winter of 1976–77. This included increasing the net apparent settling rate eight fold during ice cover. A total phosphorus model (TPM) was used in conjunction with MICH1 ;for forecasting. These forecasts indicate a steady-state total phosphorus concentration of 7 μg P/ L, given a target load recommended by the 1978 Water Quality Agreement. The projected time to obtain 95% of steady-state response to a load change was 7–14 years.     

The investigation of basic processes of rapidly hardening wood-cement-water mixture with CO2

The rapid hardening of wood-cement-water mixture in a carbon dioxide enriched environment was investigated, by studying the development of carbonation degree and monitoring the phase changes in the mixture. The carbonation reaction was a diffusion-controlled process. It occurred very quickly in the first two minutes of reaction. After that, its rate decreased drastically, due to the increasing difficulty of transporting reactants to reaction sites. Jander’s model was found ineffective in predicting the carbonation process. However, its modified version, developed by Kroger and Ziegler, could describe this progress accurately. In addition, the rapid hardening appeared to result mainly from the reactions of calcium silicates in cement with carbon dioxide. The reaction between ettringite and carbon dioxide might also contribute to this rapid hardening process. However, the reaction between calcium hydroxide and carbon dioxide was not confirmed.