Teaching old precursors new tricks: Fast room temperature synthesis of surfactant-free colloidal platinum nanoparticles
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Quinson, J. (ORCID:0000000293749330)↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Teaching Freight Mode Choice Models New Tricks Using Interpretable Machine Learning Methods
Understanding and forecasting the intricate freight mode choice behavior under various industry, policy, and technology contexts is essential in freight planning and policymaking. Numerous models have been developed in prior studies to provide insights into freight mode selection, the majority of which use discrete choice models such as multinomial logit (MNL) models. However, logit models often rely on linear specifications of independent variables, despite potential nonlinear relationships in the data. Moreover, there often lacks a heuristic and efficient approach to identify such complex relationships to define the logit model specifications. To fill this gap, we developed an MNL model for freight mode choice using the insights from state-of-the- art machine learning (ML) models. ML models can capture the nonlinear nature of the complex decision-making process, and recent advances in 'explainable AI' have greatly improved their interpretability. The interpretable ML methods help enhance the performance of MNL models and advance knowledge of freight mode choice. Specifically, the influential factors and their relationship with individual modes are identified using SHapley Additive exPlanations (SHAP) to improve the MNL's performance. The workflow is demonstrated in a case study of Austin, Texas, and the SHAP results reveal multiple nonlinear relationships predicted by ML models. Incorporating those relationships into MNL model specifications improves the interpretability and accuracy of the MNL model compared to a conventional MNL model. Findings from this study can be used to guide freight planning and inform policymakers and practitioners on how key factors affect freight decision-making.
ADVANCED PROPULSION SYSTEMS,MATHEMATICS AND COMPUT↗
Adoption of Test Driven Development and Continuous Integration for the Development of the Trick Simulation Toolkit
This paper describes the adoption of a Test Driven Development approach and a Continuous Integration System in the development of the Trick Simulation Toolkit, a generic simulation development environment for creating high fidelity training and engineering simulations at the NASA/Johnson Space Center and many other NASA facilities. It describes what was learned and the significant benefits seen, such as fast, thorough, and clear test feedback every time code is checked-in to the code repository. It also describes a system that encourages development of code that is much more flexible, maintainable, and reliable. The Trick Simulation Toolkit development environment provides a common architecture for user-defined simulations. Trick builds executable simulations using user-supplied simulation-definition files (S_define) and user supplied "model code". For each Trick-based simulation, Trick automatically provides job scheduling, checkpoint / restore, data-recording, interactive variable manipulation (variable server), and an input-processor. Also included are tools for plotting recorded data and various other supporting tools and libraries. Trick is written in C/C++ and Java and supports both Linux and MacOSX. Prior to adopting this new development approach, Trick testing consisted primarily of running a few large simulations, with the hope that their complexity and scale would exercise most of Trick's code and expose any recently introduced bugs. Unsurprising, this approach yielded inconsistent results. It was obvious that a more systematic, thorough approach was required. After seeing examples of some Java-based projects that used the JUnit test framework, similar test frameworks for C and C++ were sought. Several were found, all clearly inspired by JUnit. Googletest, a freely available Open source testing framework, was selected as the most appropriate and capable. The new approach was implemented while rewriting the Trick memory management component, to eliminate a fundamental design flaw. The benefits became obvious almost immediately, not just in the correctness of the individual functions and classes but also in the correctness and flexibility being added to the overall design. Creating code to be testable, and testing as it was created resulted not only in better working code, but also in better-organized, flexible, and readable (i.e., articulate) code. This was, in essence the Test-driven development (TDD) methodology created by Kent Beck. Seeing the benefits of Test Driven Development, other Trick components were refactored to make them more testable and tests were designed and implemented for them.
Penn, John M.↗
Trick Simulation Environment 07
The Trick Simulation Environment is a generic simulation toolkit used for constructing and running simulations. This release includes a Monte Carlo analysis simulation framework and a data analysis package. It produces all auto documentation in XML. Also, the software is capable of inserting a malfunction at any point during the simulation. Trick 07 adds variable server output options and error messaging and is capable of using and manipulating wide characters for international support. Wide character strings are available as a fundamental type for variables processed by Trick. A Trick Monte Carlo simulation uses a statistically generated, or predetermined, set of inputs to iteratively drive the simulation. Also, there is a framework in place for optimization and solution finding where developers may iteratively modify the inputs per run based on some analysis of the outputs. The data analysis package is capable of reading data from external simulation packages such as MATLAB and Octave, as well as the common comma-separated values (CSV) format used by Excel, without the use of external converters. The file formats for MATLAB and Octave were obtained from their documentation sets, and Trick maintains generic file readers for each format. XML tags store the fields in the Trick header comments. For header files, XML tags for structures and enumerations, and the members within are stored in the auto documentation. For source code files, XML tags for each function and the calling arguments are stored in the auto documentation. When a simulation is built, a top level XML file, which includes all of the header and source code XML auto documentation files, is created in the simulation directory. Trick 07 provides an XML to TeX converter. The converter reads in header and source code XML documentation files and converts the data to TeX labels and tables suitable for inclusion in TeX documents. A malfunction insertion capability allows users to override the value of any simulation variable, or call a malfunction job, at any time during the simulation. Users may specify conditions, use the return value of a malfunction trigger job, or manually activate a malfunction. The malfunction action may consist of executing a block of input file statements in an action block, setting simulation variable values, call a malfunction job, or turn on/off simulation jobs.
Lin, Alexander S.↗
The Trick Simulation Toolkit: A NASA/Opensource Framework for Running Time Based Physics Models
The Trick Simulation Toolkit is a simulation development environment used to create high fidelity training and engineering simulations at the NASA Johnson Space Center and many other NASA facilities. Its purpose is to generate a simulation executable from a collection of user-supplied models and a simulation definition file. For each Trick-based simulation, Trick automatically provides job scheduling, numerical integration, the ability to write and restore human readable checkpoints, data recording, interactive variable manipulation, a run-time interpreter, and many other commonly needed capabilities. This allows simulation developers to concentrate on their domain expertise and the algorithms and equations of their models. Also included in Trick are tools for plotting recorded data and various other supporting utilities and libraries. Trick is written in C/C++ and Java and supports both Linux and MacOSX computer operating systems. This paper describes Trick's design and use at NASA Johnson Space Center.
Penn, John M.↗
An Old Dog and New Tricks
As I approach my 55th birthday, the old adage 'you can't teach an old dog new tricks' keeps coming to mind. I'm not sure why, because I don't feel old and I'm still interested in taking on new challenges and learning new tricks. However, as I mentor new project managers, I am also aware that others may consider me an old dog unable to learn new tricks. To the contrary, the people I mentor continue to teach me new tricks and challenge my assumptions about project management.
Cameron, W. Scott↗
The Trick Simulation Toolkit: A NASA/Open source Framework for Running Time Based Physics Models
This paper describes the design and use at of the Trick Simulation Toolkit, a simulation development environment for creating high fidelity training and engineering simulations at the NASA Johnson Space Center and many other NASA facilities. It describes Trick's design goals and how the development environment attempts to achieve those goals. It describes how Trick is used in some of the many training and engineering simulations at NASA. Finally it describes the Trick NASA/Open source project on Github.
Penn, John M.↗
Timing Tricks For Complicated Accelerators [PowerPoint]
A brief description of the Los Alamos Neutron Science Center is given first, including static and dynamic scheduling. The principal tricks presented are prescient feed forward and pulser replication. Tricks with flip/flop pulsers are also included.
43 PARTICLE ACCELERATORS↗
Molecular replacement: tricks and treats
To be successful, molecular replacement relies on the quality of the model and of the crystallographic data. Some tricks that could be applied to the models or to the crystal to increase the success rate of MR are discussed here. Molecular replacement is the method of choice for X-ray crystallographic structure determination provided that suitable structural homologues are available in the PDB. Presently, there are ∼80 000 structures in the PDB (8074 were deposited in the year 2012 alone), of which ∼70% have been solved by molecular replacement. For successful molecular replacement the model must cover at least 50% of the total structure and the C{sub α} r.m.s.d. between the core model and the structure to be solved must be less than 2 Å. Here, an approach originally implemented in the CaspR server (http://www.igs.cnrs-mrs.fr/Caspr2/index.cgi) based on homology modelling to search for a molecular-replacement solution is discussed. How the use of as much information as possible from different sources can improve the model(s) is briefly described. The combination of structural information with distantly related sequences is crucial to optimize the multiple alignment that will define the boundaries of the core domains. PDB clusters (sequences with ≥30% identical residues) can also provide information on the eventual changes in conformation and will help to explore the relative orientations assumed by protein subdomains. Normal-mode analysis can also help in generating series of conformational models in the search for a molecular-replacement solution. Of course, finding a correct solution is only the first step and the accuracy of the identified solution is as important as the data quality to proceed through refinement. Here, some possible reasons for failure are discussed and solutions are proposed using a set of successful examples.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Remote detectability from entanglement bootstrap I: Kirby’s torus trick
Remote detectability is often taken as a physical assumption in the study of topologically ordered systems, and it is a central axiom of mathematical frameworks of topological quantum field theories. We show under the entanglement bootstrap approach that remote detectability is a necessary property; that is, we derive it as a theorem. Starting from a single wave function on a topologically-trivial region satisfying the entanglement bootstrap axioms, we can construct states on closed manifolds. The crucial technique is to immerse the punctured manifold into the topologically trivial region and then heal the puncture. This is analogous to Kirby’s torus trick. We then analyze a special class of such manifolds, which we call pairing manifolds. For each pairing manifold, which pairs two classes of excitations, we identify an analog of the topological S S -matrix. This pairing matrix is unitary, which implies remote detectability between two classes of excitations. These matrices are in general not associated with the mapping class group of the manifold. As a by-product, we can count excitation types (e.g., graph excitations in 3+1d). The pairing phenomenon occurs in many physical contexts, including systems in different dimensions, with or without gapped boundaries. We provide a variety of examples to illustrate its scope.
Shi, Bowen (ORCID:0000000206899964)↗
Tritium trick
Large controlled amounts of helium in uniform concentration in thick samples can be obtained through the radioactive decay of dissolved tritium gas to He3. The term, tritium trick, applies to the case when helium, added by this method, is used to simulate (n,alpha) production of helium in simulated hard flux radiation damage studies.
Green, W. V.↗
Teamcenter community : administration tips and tricks
This presentation covers what areas of prerequisites are important to understand and how one can improve performance and maintenance of an existing implementation. It will also cover tips and tricks for site migration and how to plan for upgrades.
teamcenter↗
Testability, Test Automation and Test Driven Development for the Trick Simulation Toolkit
This paper describes the adoption of a Test Driven Development approach and a Continuous Integration System in the development of the Trick Simulation Toolkit, a generic simulation development environment for creating high fidelity training and engineering simulations at the NASA Johnson Space Center and many other NASA facilities. It describes the approach, and the significant benefits seen, such as fast, thorough and clear test feedback every time code is checked into the code repository. It also describes an approach that encourages development of code that is testable and adaptable.
Penn, John↗
A new trick for an old support: Stabilizing gold single atoms on LaFeO 3 perovskite
Single-atom catalysts (SACs) have shown great potential for achieving superior catalytic activity due to maximizing metal efficiency. The key obstacle in developing SACs lies in the availability of supports that can stabilize SACs. Here we report the first successful development of single gold (Au) atom catalysts supported on high-surface-area hierarchical perovskite oxides. The resulting Au single-atoms are extremely stable at calcination temperatures up to 700 °C in air and under reaction conditions. A high catalytic activity for CO oxidation and distinct self-activating property were also achieved. Furthermore, evidenced by theoretical calculations and experimental studies including X-ray absorption fine structures and in situ Fourier-transform infrared spectra, the surface Au active sites are confirmed to be predominately positively charged. This study provides a generalizable approach to fabricating highly stable Au single-atom catalysts with tunable catalytic performance, and we anticipate that this discovery will facilitate new possibilities for the development of single atom catalysts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Old drug new tricks: Chlorhexidine acts as a potential allosteric inhibitor toward PAK1
This paper describes the identification of chlorhexidine, an agent commonly used in clinical as a novel potential allosteric inhibitor of PAK1. In cellular assays, chlorhexidine showed a good inhibitory profile, and its inhibitory profile was even better than IPA-3, a well-known allosteric inhibitor. In pharmacology experiments, chlorhexidine successfully inhibited the relief of PAK1 dimer and inhibited the activation of PAK1. Our findings offer an insight for the new drug development of PAK1 inhibitor. We also provide a possible explanation for the phenomenon that the application of the chlorhexidine in peritoneal lavage inhibited the development of tumor.
60 APPLIED LIFE SCIENCES↗
Teaching an Old Reagent New Tricks: Synthesis, Unusual Reactivity, and Solution Dynamics of Borohydride Grignard Compounds
Grignard reagents of general formula RMgX (X = Cl - , Br - , I - ) have been utilized in various chemistries for over 100 years. Here, we report that replacing the halide in a Grignard reagent with a reactive borohydride anion adds a new synthetic dimension for these influential compounds. Here, we synthesized the series RMgBH 4 (R=Et, n-Bu, Ph, Bn) and characterized the reactivity toward both organic and inorganic molecules. Using butylmagnesium borohydride (BuMgBH 4 ) as an exemplar, we demonstrate that these compounds possess unique reactivity due to the presence of reducing borohydride groups, resulting in tandem reactivity with organic amides/esters to generate secondary and primary alcohols. Molecular dynamics simulations indicate the stability of BuMgBH 4 is comparable to that of Mg(BH 4 ) 2 + MgBu 2 , validating the Schlenk equilibrium in borohydride Grignard compounds. Metadynamics simulations confirm that the equilibrium is kinetically accessible through solvent-mediated processes. BuMgBH 4 also reacts with CO 2 and NH 3 , revealing potential uses for CO 2 utilization and as a mixed-anion metal borohydride/amide precursor.
36 MATERIALS SCIENCE↗
A Double-Hotdog with a New Trick: Structure and Mechanism of the trans-Acyltransferase Polyketide Synthase Enoyl-isomerase
Abstract not provided
Gay, Darren C.↗