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At least 379 records · Page 21

CGSim: A Simulation Framework for Large Scale Distributed Computing Environment

Large-scale distributed computing infrastructures such as the Worldwide LHC Computing Grid (WLCG) require comprehensive simulation tools for evaluating performance, testing new algorithms, and optimizing resource allocation strategies. However, existing simulators suffer from limited scalability, hardwired algorithms, lack of real-time monitoring, and inability to generate datasets suitable for modern machine learning approaches. We present CGSim, a simulation framework for large-scale distributed computing environments that addresses these limitations. Built upon the validated SimGrid simulation framework, CGSim provides high-level abstractions for modeling heterogeneous grid environments while maintaining accuracy and scalability. Key features include a modular plugin mechanism for testing custom workflow scheduling and data movement policies, interactive real-time visualization dashboards, and automatic generation of event-level datasets suitable for AI-assisted performance modeling. We demonstrate CGSim’s capabilities through a comprehensive evaluation using production ATLAS PanDA workloads, showing significant calibration accuracy improvements across WLCG computing sites. Scalability experiments show near-linear scaling for multi-site simulations, with distributed workloads achieving 6 × better performance compared to single-site execution. The framework enables researchers to simulate WLCG-scale infrastructures with hundreds of sites and thousands of concurrent jobs within practical time budget constraints on commodity hardware.

Vatsavai, Sairam Sri [Brookhaven National Laborato↗

A Satellite Assessment of the Urban Heat Island in Morocco

Urban ecosystems interact with surroundings via land cover changes and their subsequent impact on surface temperature. In emerging countries, large urban agglomerations often form around cities, and only few studies have evaluated their impact. This study carries out the first ever large-scale assessment of urban heat island (UHI) and reflects on its mitigation in Morocco.The analysis reveals a well-defined UHI in urban-areas built within vegetated lands and an urban heat sink (UHS) in urban-areas built within arid regions. Both UHI and UHS amplitudes are higher during day than nighttime, emphasizing vegetation physiological activity. We show a monotonic increase in UHI amplitude with urban-area size. However, unlike previous studies, our analysis shows that as urban-areas built in desert-like environments grow in size, the UHS gradually decreases to ultimately turn into an UHI. On average, cities built within vegetation are warmer than rural fringe by 1.51°C during daytime. This suggests that daytime urban heating may exacerbate the potential climate warming. Our results also suggest that adapted trees constitute a natural cooling mechanism and should be part of urban heating mitigation in Morocco.

Urban Heat Sink↗

Turbulent Premixed Flame Propagation in Microgravity

A facility in which turbulent Couette flow could be generated in a microgravity environment was designed and built. To fit into the NASA Lewis drop tower the device had to be very compact. This means that edge effects and flow re-circulation were expected to affect the flow. The flow was thoroughly investigated using LDV and was found to be largely two dimensional away from the edges with constant turbulence intensities in the core. Slight flow asymmetries are introduced by the non symmetric re-circulation of the fluid outside the test region. Belt flutter problems were remedied by adding a pair of guide plates to the belt. In general, the flow field was found to be quite similar to previously investigated Couette flows. However, turbulence levels and associated shear stresses were higher. This is probably due to the confined re-circulation zone reintroducing turbulence into the test section. An estimate of the length scales in the flow showed that the measurements were able to resolve nearly all the length scales of interest. Using a new LES method for subgrid combustion it has been demonstrated that the new procedure is computational feasible even on workstation type environment. It is found that this model is capable of capturing the propagation of the premixed names by resolving the flame in the LES grid within 2-3 grid points. In contrast, conventional LES results in numerical smearing of the flame and completely inaccurate estimate of the turbulent propagation speed. Preliminary study suggests that there is observable effect of buoyancy in the 1g environment suggesting the need for microgravity experiments of the upcoming experimental combustion studies. With the cold flow properties characterized, an identical hot flow facility is under construction. It is assumed that the turbulence properties ahead of the flame in this new device will closely match the results obtained here. This is required since the hot facility will not enable LDV measurements. The reacting flow facility is also being constructed with planned drop tower experiments in mind. Therefore, issues related to safety and structural integrity are being take into account. Further development of the numerical model will also be carried out to include finite-rate kinetics for representative premixed cases. More detail analysis of the flame structure and propagation nature will be investigated. Simulations will also be compared to the flame properties observed in the experiments.

Menon, S.↗

Radiation Tolerance and Mechanical Properties of Nanostructured Amorphous-Ceramic/Metal Composites

The objective of this work was to use a radically non-traditional approach to design amorphous-ceramic/metal composites for service in extreme irradiation environments. The project was built on a strong integration among four research teams for materials synthesis and characterization, ion irradiation, mechanical evaluation, and atomic scale modeling. Rather than try to prevent microstructure changes in polycrystalline aggregates, the research team worked to evolve composite systems where one of the constituents is intentionally synthesized in a non-crystalline or “amorphous” state. Because amorphous materials possess no translational symmetry, such alloys do not contain conventional crystal defects such as vacancies, interstitials, or dislocations. These materials offer the possibility of eliminating the root cause responsible for radiation damage in polycrystalline solids - namely the production of point defects and clusters thereof in collision cascades - and could serve as the basis for developing a new class of structural materials with unprecedented resistance to radiation. The amorphous alloys were used to develop advanced amorphous-ceramic/metal composites with greatly improved radiation tolerance and stability above 500oC, and improved mechanical performance by combining the good properties of amorphous materials (high strength and elastic limit) with those of crystalline materials (high toughness, strain hardening). The ceramic component of the composite consisted of a high crystallization temperature and radiation tolerant amorphous alloy composed of Si-O-C, silicon oxycarbide, while the metal layer was Fe and Fe(Cr), chosen to serve as model materials for steel. A prime hypothesis that drove this work is that the composite interface, together with the composite constituents, would provide significantly enhanced radiation tolerance, similar to or superior to those observed in metallic nanolayered structures, in a more engineering relevant material system. As our experimental data and modeling show, we have successfully developed a new class of ceramic/metal composites that can be adapted for engineering applications, thus significantly impacting improved materials performance for advanced nuclear reactors.

36 MATERIALS SCIENCE↗

Performance of a Drifting Acoustic Instrumentation SYstem (DAISY) for characterizing radiated noise from marine energy converters

Marine energy converters can generate electricity from energetic ocean waves and water currents. Because sound is extensively used by marine animals, the radiated noise from these systems is of regulatory interest. However, the energetic nature of these locations poses challenges for performing accurate passive acoustic measurements, particularly with stationary platforms. The Drifting Acoustic Instrumentation SYstem (DAISY) is a modular hydrophone recording system purpose-built for marine energy environments. Using a flow shield in currents and mass–spring–damper suspension system in waves, we demonstrate that DAISYs can effectively minimize the masking effect of flow noise at frequencies down to 10 Hz. In addition, we show that groups of DAISYs can utilize time-delay-of-arrival post-processing to attribute radiated noise to a specific source. Consequently, DAISYs can rapidly measure radiated noise at all frequencies of interest for prototype marine energy converters. Furthermore, the resulting information from future operational deployments should support regulatory decision-making and allow technology developers to make design adjustments that minimize the potential for acoustic impacts as their systems are scaled up for utility-scale power generation.

16 TIDAL AND WAVE POWER↗

Toward dynamic urban environmental exposure assessments in mental health research

Highlights: • The environmental context affects people's mental health. • Environmental exposure assessments are frequently restricted to the neighborhoods in which people currently live. • Dynamic exposures along people's daily paths may trigger mental disorders. • Exposures over people's residential history might affect mental health later in life. • Only dynamic exposure assessments enable the inclusion of the duration and sequence of exposures and risk accumulation over time. It is increasingly recognized that mental disorders are affected by both personal characteristics and environmental exposures. The built, natural, and social environments can either contribute to or buffer against metal disorders. Environmental exposure assessments related to mental health typically rely on neighborhoods within which people currently live. In this article, I call into question such neighborhood-based exposure assessments at one point in time, because human life unfolds over space and across time. To circumvent inappropriate exposure assessments and to better grasp the etiologies of mental disease, I argue that people are exposed to multiple health-supporting and harmful exposures not only during their daily lives, but also over the course of their lives. This article aims to lay a theoretical foundation elucidating the impact of dynamic environmental exposures on mental health outcomes. I examine, first, the possibilities and challenges for mental health research to integrate people's environmental exposures along their daily paths and, second, how exposures over people's residential history might affect mental health later in life. To push the borders of scientific inquiries, I stress that only such mobility-based approaches facilitate an exploration of exposure duration, exposure sequences, and exposure accumulation.

54 ENVIRONMENTAL SCIENCES↗

A junction-tree based learning algorithm to optimize network wide traffic control: A coordinated multi-agent framework

Our study develops a novel reinforcement learning algorithm for the challenging coordinated signal control problem. Traffic signals are modeled as intelligent agents interacting with the stochastic traffic environment. The model is built on the framework of coordinated reinforcement learning. The Junction Tree Algorithm (JTA) based reinforcement learning is proposed to obtain an exact inference of the best joint actions for all the coordinated intersections. Moreover, the algorithm is implemented and tested with a network containing 18 signalized intersections in VISSIM. Finally, our results show that the JTA based algorithm outperforms independent learning (Q-learning), real-time adaptive learning, and fixed timing plans in terms of average delay, number of stops, and vehicular emissions at the network level.

97 MATHEMATICS AND COMPUTING↗

The ASACUSA Micromegas Tracker: A cylindrical, bulk Micromegas detector for antimatter research

The ASACUSA Micromegas Tracker (AMT; ASACUSA: Atomic Spectroscopy and Collisions Using Slow Antiprotons) was designed to be able to reconstruct antiproton-nucleon annihilation vertices in three dimensions. The goal of this device is to study antihydrogen formation processes in the ASACUSA cusp trap, which was designed to synthesise a spin-polarised antihydrogen beam for precise tests of Charge, Parity, and Time (CPT) symmetry invariance. This paper discusses the structure and technical details of an AMT detector built into such an environment, its data acquisition system and the first performance with cosmic rays.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Temperature Field Reconstruction of Surfaces Heated Through Radiative Heat Transfer Using Convolutional Neural Networks

Microreactors could play a crucial role in decarbonizing our energy portfolio. However, their development and implementation come with specific challenges, particularly regarding cost. Due to their compact size and the harsh operational environment, collecting real-time data on reactor operation can be challenging. Many probe designs are unable to withstand extreme conditions (e.g., temperature, radiation) in the reactor. In this context, using convolutional neural networks (CNNs) can pave the way for developing a nonintrusive approach that relies solely on ex-core sensors. A well-trained physics-informed CNN can reconstruct the distribution of a given physical quantity over a domain using only a few sensors, allowing us to reconstruct the desired field distribution even in a limited space or complex geometries where a large array of sensors is impractical. In this work, we present the initial steps toward developing a real-time tool for monitoring the thermal behavior of nuclear reactor pressure vessels. Based on an experimental setup, a computational model using the Multiphysics Object-Oriented Simulation Environment (moose) framework was built, where the Ray Tracing and Heat Conduction modules were used to evaluate the temperature distribution over a convex metal surface heated through radiative heat transfer. This metal surface represents a section of a heated nuclear reactor vessel wall. The model also accounts for solid mechanics physics through the moose Solid Mechanics module. In situ experimental data, acquired from a Texas A&M facility, were used to validate the computational model. Part of the data generated by the moose model was used to train the convolutional neural network to reconstruct the vessel wall's outer surface temperature. The CNN generalization was then compared against the experimental and computational data.

Aldeia Machado, Luiz Carlos↗

Exploration of Preterm Birth Rates Using the Public Health Exposome Database and Computational Analysis Methods

Recent advances in informatics technology has made it possible to integrate, manipulate, and analyze variables from a wide range of scientific disciplines allowing for the examination of complex social problems such as health disparities. This study used 589 county-level variables to identify and compare geographical variation of high and low preterm birth rates. Data were collected from a number of publically available sources, bringing together natality outcomes with attributes of the natural, built, social, and policy environments. Singleton early premature county birth rate, in counties with population size over 100,000 persons provided the dependent variable. Graph theoretical techniques were used to identify a wide range of predictor variables from various domains, including black proportion, obesity and diabetes, sexually transmitted infection rates, mother’s age, income, marriage rates, pollution and temperature among others. Dense subgraphs (paracliques) representing groups of highly correlated variables were resolved into latent factors, which were then used to build a regression model explaining prematurity (R-squared = 76.7%). Two lists of counties with large positive and large negative residuals, indicating unusual prematurity rates given their circumstances, may serve as a starting point for ways to intervene and reduce health disparities for preterm births

Environmental Sciences & Ecology↗

Double-lunar swingby trajectories for the spacecraft of the International Solar Terrestrial Physics program

The ISEE-3 satellite carried out the first extensive exploration of the distant geomagnetic tail during 1983. ISEE-3's orbit was altered with four lunar gravity assists that alternately decreased and increased its orbital energy while keeping the apogees aligned in the antisolar direction. Two spacecraft of the International Solar Terrestrial Physics program will use similar double-lunar swingby orbits to study the solar wind and the geomagnetic environment. Geotail will be built in Japan for the Institute of Space and Astronautical Sciences; its main purpose will be to explore the earth's geomagnetic tail. Wind is a NASA spacecraft that will monitor the solar wind upstream from the earth and will also study the bowshock region of the magnetosphere. Current plans call for launches of both by NASA with expendable launch vehicles during the second half of 1992.

Dunham, David W.↗

Transportable Applications Environment (TAE) Plus: A NASA tool used to develop and manage graphical user interfaces

The Transportable Applications Environment (TAE) Plus was built to support the construction of graphical user interfaces (GUI's) for highly interactive applications, such as real-time processing systems and scientific analysis systems. It is a general purpose portable tool that includes a 'What You See Is What You Get' WorkBench that allows user interface designers to layout and manipulate windows and interaction objects. The WorkBench includes both user entry objects (e.g., radio buttons, menus) and data-driven objects (e.g., dials, gages, stripcharts), which dynamically change based on values of realtime data. Discussed here is what TAE Plus provides, how the implementation has utilized state-of-the-art technologies within graphic workstations, and how it has been used both within and without NASA.

Szczur, Martha R.↗

An iconic programming language for sensor-based robots

In this paper we describe an iconic programming language called Onika for sensor-based robotic systems. Onika is both modular and reconfigurable and can be used with any system architecture and real-time operating system. Onika is also a multi-level programming environment wherein tasks are built by connecting a series of icons which, in turn, can be defined in terms of other icons at the lower levels. Expert users are also allowed to use control block form to define servo tasks. The icons in Onika are both shape and color coded, like the pieces of a jigsaw puzzle, thus providing a form of error control in the development of high level applications.

Gertz, Matthew↗

Parallelized direct execution simulation of message-passing parallel programs

As massively parallel computers proliferate, there is growing interest in findings ways by which performance of massively parallel codes can be efficiently predicted. This problem arises in diverse contexts such as parallelizing computers, parallel performance monitoring, and parallel algorithm development. In this paper we describe one solution where one directly executes the application code, but uses a discrete-event simulator to model details of the presumed parallel machine such as operating system and communication network behavior. Because this approach is computationally expensive, we are interested in its own parallelization specifically the parallelization of the discrete-event simulator. We describe methods suitable for parallelized direct execution simulation of message-passing parallel programs, and report on the performance of such a system, Large Application Parallel Simulation Environment (LAPSE), we have built on the Intel Paragon. On all codes measured to date, LAPSE predicts performance well typically within 10 percent relative error. Depending on the nature of the application code, we have observed low slowdowns (relative to natively executing code) and high relative speedups using up to 64 processors.

Dickens, Phillip M.↗

Testing, Modeling and System Impact of Metabolic Heat Regenerated Temperature Swing Adsorption

Metabolic heat regenerated temperature swing adsorption (MTSA) technology is being developed for removal and rejection of carbon dioxide (CO2) and heat from a portable life support system (PLSS) to the Martian environment. Previously, hardware was built and tested to demonstrate using heat from simulated, dry ventilation loop gas to affect the temperature swing required to regenerate an adsorbent used for CO2 removal. New testing has been performed using a moist, simulated ventilation loop gas to demonstrate the effects of water condensing and freezing in the heat exchanger during adsorbent regeneration. In addition, thermal models of the adsorbent during regeneration were modified and calibrated with test data to capture the effect of the CO2 heat of desorption. Finally, MTSA impact on PLSS design was evaluated by performing thermal balances assuming a specific PLSS architecture. Results using NASA s Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT), a PLSS system evaluation tool, are presented.

Lacomini, Christine S.↗

Success in commissioning a key U.S. radioactive waste burial site through the technical support of Dufrane Nuclear Shielding Incorporated (DNSI) - 15476

With the -phase out- of the South Carolina based Barnwell Radioactive Waste Burial Site, and the stockpile and storage of radioactive waste and irradiated components throughout the U.S. Nuclear Industry for decades, the opening of the Texas Low-Level Radioactive Waste Disposal Compact Facility by Waste Control Specialists (WCS), is a game changer in solving this industry-wide issue. For the first time in decades, generators now have the opportunity to send their waste to a site specifically designed to permanently sequester the waste in a licensed facility that will protect public health and the environment, better than any built to date. As history has shown through the many decades of the U.S. Commercial and Federal Nuclear Industry, site operators and management have relied heavily on contractors and vendors with exceptional expertise and decades of experience to achieve success and meet their goals. The commissioning of WCS was no exception as DNSI was contracted to design, develop, build and deploy a major component required for the opening and successful operation of the WCS site. This component, being the Modular Concrete Canister (MCC), is the -work horse- of the site. With its enormous size, weight and strength, it provides many functions that meet and comply with the site performance assessment (PA) under 10 CFR Part 61, the site WAC, and Texas Low-Level Radioactive Waste Disposal Authority. Offsite contracting the production and delivery of this critical component was a major step toward success in meeting schedule and cost for the much needed opening of the Texas Compact and Federal site. In selecting a shielding vendor, WCS partnered with a U.S. Nuclear Service company with over 30 years of experience which spans the entire U.S. Commercial, Federal, and Nuclear Industry. The task given DNSI was not a simple one, it involved every aspect from start to finish of the design, production and delivery of rectangular, cylindrical and -irradiated hardware- (IH) MCCs, that could accept waste up to 100 Sv /Hr contact dose rates. The enormity of this project was quite clear and required extensive quality control, construction of batch plants, purchase of huge quantities of raw materials, setting up a production site in a neighboring city, relocation of personnel from company headquarters, and safely transporting 8,000 Tons of MCC components 75 miles one-way on West Texas highways daily. Most important of all, this was accomplished safely with no incidents, no component failures or rejects, and on schedule. The start of receipt, of -in-compact waste- and -out-of-compact waste- was conducted virtually in a 3 month period time span. To help guarantee success and quality of product, all forms had surfaces machined, heavy duty elastomer coatings were applied to concrete surfaces, only galvanized anchors were used, and the batch plant was run to strict ASME standards thus testing every 50 cubic yards of concrete poured. With significant teamwork and success from Vendors such as DNSI, WCS and the Texas Compact has evolved as one of the leading radioactive waste sites in the U.S. and the world, providing safe, secure and compliant permanent waste disposal services by using technical expertise and innovation of the highest standards. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

GENIE Flight Test Results and System Overview

NASA has envisioned a suite of lander test vehicles that will be flown in Earth s atmosphere to incrementally demonstrate applicable lunar lander performance in the terrestrial environment. As each terrestrial rocket progresses in maturity, relevant space flight technology matures to a higher technology readiness level, preparing it for inclusion on a future lunar lander design.. NASA s "Project M" lunar mission concept flew its first terrestrial rocket, RR1, in June 2010 in Caddo Mills, Texas. The Draper Laboratory built GENIE (Guidance Embedded Navigator Integration Environment) successfully demonstrated accurate, real time, embedded performance of Project M navigation and guidance algorithms in a highly dynamic environment. The RR1 vehicle, built by Armadillo Aerospace, performed a successful 60 second free flight and gave the team great confidence in Project M s highly reliable and robust GNC system design and implementation. This paper provides an overview of the GENIE system and describes recent flight performance test results onboard the RR1 terrestrial rocket.

Brady, Tye↗

NASTRAN used in a production environment

A finite element analysis procedure built around the NASTRAN system is assessed. A number of support programs that were either written or modified to interface with NASTRAN and some improvements that were made to NASTRAN itself are noted. Some typical models are analyzed and an actual schedule is followed for constructing and analyzing the models to support a large design program.

Wilkinson, R. F.↗