Examination of the Circle Spline Routine

The Circle Spline routine is currently being used for generating both two and three dimensional spline curves. It was developed for use in ESCHER, a mesh generating routine written to provide a computationally simple and efficient method for building meshes along curved surfaces. Circle Spline is a parametric linear blending spline. Because many computerized machining operations involve circular shapes, the Circle Spline is well suited for both the design and manufacturing processes and shows promise as an alternative to the spline methods currently supported by the Initial Graphics Specification (IGES)

Density effect of inspection data points in as-built modeling of parts

At Los Alamos National Laboratory, the use of inspection data generated at various stages of the life cycle of a product is being investigated in a feedback process to the design engineers and physicists. This data will be used to determine through analysis how to optimize assembly, mitigate nominal deviations, and confront aging issues. This as-built engineering philosophy characterizes a system through the topographical data generated through inspection. Through intricate modeling techniques, the topographical definition gives rise to a solid model in a Computer Aided Engineering (CAE) software package such as Parametric Technologies Pro/ENGINEER{trademark}. Once a solid model has been built, the definition can be used for a variety of analytical purposes including mass property calculations, finite element model generation, and virtual environment generation. A strictly analytical approach was used to exercise the as-built engineering method in characterizing components. A hypothetical component was used and mass properties were calculated analytically to provide nominal definition. This was then compared to mass properties calculated as a result of modeling theoretical inspection data in two formats; manual-collected data such as that obtained from a Coordinate Measuring Machine (specifically the Brown and Sharp) inspection process and automated-collected data such as obtained from a Sheffield inspection process. Mass properties calculated from a solid model generated using the Pro/ENGINEER{trademark} modeling operations were also compared with the nominal definition

Principles of models based engineering

This report describes a Models Based Engineering (MBE) philosophy and implementation strategy that has been developed at Los Alamos National Laboratory`s Center for Advanced Engineering Technology. A major theme in this discussion is that models based engineering is an information management technology enabling the development of information driven engineering. Unlike other information management technologies, models based engineering encompasses the breadth of engineering information, from design intent through product definition to consumer application

Principles of As-Built Engineering

As-Built Engineering is a product realization methodology founded on the notion that life-cycle engineering should be based on what is actually produced and not on what is nominally designed. As-Built Engineering is a way of thinking about the production realization process that enables customization in mass production environments. It questions the relevance of nominal based methods of engineering and the role that tolerancing plays in product realization. As-Built Engineering recognizes that there will always be errors associated with manufacturing that cannot be controlled and therefore need to be captured in order to fully characterize each individual product`s unique attributes. One benefit of As-Built Engineering is the ability to provide actual product information to designers and analysts enabling them to verify their assumptions using actual part and assembly data. Another benefit is the ability to optimize new and re-engineered assemblies

The value of the Duke Activity Status Index (DASI) in predicting ischaemia in myocardial perfusion scintigraphy — a prospective study

BACKGROUND: Functional capacity assessment may be a useful tool to stratify patients according to risk of coronary artery disease (CAD). The Duke Activity Status Index (DASI) is a functional assessment based on activities of daily living and cardiovascular fitness, assessed using a self-administered questionnaire. MATERIAL AND METHODS: We assessed the relationship between established clinical risk factors for CAD and the DASI with results of myocardial perfusion scintigraphy (MPS). The MPS results used in the analysis were the presence of reversible ischaemia and the resting left ventricular ejection fraction (LVEF). A DASI self-administered questionnaire was completed by 117 consecutive participants, and a patient history was taken to ascertain established risk factors. All participants underwent a stress test, and myocardial perfusion scintigraphy was performed. Statistical analysis consisted of logistic and linear regression using a statistical software package. RESULTS: The DASI was the only factor that correlated significantly with reversible ischaemia on MPS. None of the previously established risk factors had a significant association with reversible ischaemia within the model. Our study found a potential relationship between the DASI score and the left ventricular ejection fraction (LVEF) although this was not statistically significant. CONCLUSIONS: Our study findings suggest that the DASI may represent a powerful tool for risk stratification prior to investigation of CAD. A further study with a larger sample size will be required to investigate the predictive value of the DASI and the association with LVEF. Nuclear Med Rev 2010; 13, 2: 59–6

Building protypes of damaged systems from analysis simulations

Our rapid prototype of damaged systems project seeks to provide a technology for allowing engineers to build demonstration prototypes of damaged products from analysis post-processing data. Most commercial finite element programs do not have a capability to construct deformed geometry at the conclusion of an analysis simulation. It is therefore not presently possible to build prototypes of predicted states of a product as the result of being subjected to simulated adverse environments. Our approach is to reverse engineer a description of a deformed finite element mesh into a stereolithography format for prototyping using a Selective Laser Sintering (SLS) machine. This stereolithography file can be generated from deformed surface node information as well as from a reconstructed surface defined by inspection data. We are developing software to allow users to represent a part or assembly in a deformed condition. The damaged part can then be manufactured using the SLS process for visualization and assessment purposes. The resulting representation can also be used to create simulated X-rays of a damaged or deformed configuration for comparison with experimental test results or field data. This allows engineers to benchmark their analysis methods and provide increased understanding of analysis results through enhanced visualization. The process of reverse engineering `in-use` or damaged products allows for a more refined inspection and comparison of imperfect parts. It addresses the issue of whether or not a part will still work when subjected to certain environments or scenarios. Answers to this question can be found using our model reconstruction technique that represents an `as- built` engineering model configuration. An additional feature of this reverse engineering process is product benchmarking and closer engineer/manufacturer interactions

Enhanced product realization techniques using as-built and model reconstruction technologies

Los Alamos National Laboratory`s Center for Advanced Engineering Technology has developed a product realization process designed to enhance the complexity and comprehensiveness of the information fed back to the designer after the analytical and manufacturing operations have been completed. This process uses principles of As-Built Engineering and Model Reconstruction in a Models Based Engineering environment, allowing optimization in the manufacturing and assembly operations and providing information as to the As-Built configuration to engineering and physics designers for evaluation. As-Built Engineers is a product realization methodology founded on the notion that life-cycle engineering should be based on what is actually produced and not on what is nominally designed. It enables customization in mass production environments and questions nominal based methods of engineering. Model Reconstruction provides the capability of subjecting a design to adverse conditions within the computer aided environment and building a stereolithography model and simulated radiograph from the analytical finite element information of the simulated damaged part. Models Based Engineering is an information management tool and a key driver toward the development of adaptive product realization infrastructures. It encompasses the breadth of engineering information, from concept through design to product application

Structure and mechanism of acetolactate decarboxylase

Acetolactate decarboxylase catalyzes the conversion of both enantiomers of acetolactate to the (R)-enantiomer of acetoin, via a mechanism that has been shown to involve a prior rearrangement of the non-natural (R)-enantiomer substrate to the natural (S)-enantiomer. In this paper, a series of crystal structures of ALDC complex with designed transition state mimics are reported. These structures, coupled with inhibition studies and site-directed mutagenesis provide an improved understanding of the molecular processes involved in the stereoselective decarboxylation/protonation events. A mechanism for the transformation of each enantiomer of acetolactate is proposed