Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “connect”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Isolation and Connectivity in Random Geometric Graphs with Self-similar Intensity Measures

Random geometric graphs consist of randomly distributed nodes (points), with pairs of nodes within a given mutual distance linked. In the usual model the distribution of nodes is uniform on a square, and in the limit of infinitely many nodes and shrinking linking range, the number of isolated nodes is Poisson distributed, and the probability of no isolated nodes is equal to the probability the whole graph is connected. Here we examine these properties for several self-similar node distributions, including smooth and fractal, uniform and nonuniform, and finitely ramified or otherwise. We show that nonuniformity can break the Poisson distribution property, but it strengthens the link between isolation and connectivity. It also stretches out the connectivity transition. Finite ramification is another mechanism for lack of connectivity. The same considerations apply to fractal distributions as smooth, with some technical differences in evaluation of the integrals and analytical arguments.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Ecological connectivity and in-kind mitigation in a regulatory decision framework: A case study with an amphibian habitat specialist

Ecological connectivity is critical to the survival and long-term viability of populations but is often overlooked in regulatory frameworks. We integrated landscape-level processes into a mitigation strategy for impacts to aquatic resources on the U.S. Department of Energy (DOE) Oak Ridge Reservation (ORR) in eastern Tennessee. Wetlands on the ORR, which contain significant breeding populations of the imperiled four-toed salamander (Hemidactylium scutatum) and tubercled rein orchid (Platanthera flava var. herbiola), will be impacted by construction of an environmental waste disposal facility under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). Here, we used a modified Kepner-Tregoe decision analysis to select general mitigation options that balanced regulatory requirements and interest group perspectives. We emphasized habitat connectivity through models that prioritized an area's importance to natural area connectivity (centrality) and maintenance of population structure for an affected habitat specialist (four-toed salamanders). We also emphasized in-kind mitigation through the preservation and enhancement of ecologically similar resources and the translocation and establishment of a new subpopulation of four-toed salamanders elsewhere on the ORR. We ultimately released over 500 juvenile salamanders that originated from the impacted site into the chosen mitigation wetlands. By doing so under the constraints of a time-sensitive CERCLA remediation effort and exceeding its substantive requirements, this work underscores feasibility. Ecological connectivity and the conservation of species that are not afforded explicit regulatory processes can be effectively and efficiently integrated into environmental decision-making and land use planning.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Unique (3,8)-connected lanthanide arenedisulfonate metal-organic frameworks containing benzimidazole-5,6-dicarboxylic acid co-ligand: Syntheses, structures and luminescence

Two isostructural 3D lanthanide arenedisulfonate metal-organic frameworks (MOFs) [Ln(Hbidc)(nds){sub 0.5}(H{sub 2}O)]{sub n}(Ln=Eu(1), La(2)) have been successfully synthesized by the hydrothermal reaction of lanthanide oxide with 2,6-naphthalenedisulfonate sodium (Na{sub 2}nds) and an auxiliary ligand, 1H-benzimidazole-5,6-dicarboxylic acid (H{sub 3}bidc). The two complexes are both constructed from 2D [Ln(Hbidc)]{sup +} double layers pillared by nds{sup 2−} ligands to generate 3D (3, 8)-connected open-framework structures with 1D long narrow channels running along the a axis. From topological point of view, the 3D framework is a (3, 8)-connected tfz-d net. The weak interactions including N–H⋯O, O–H⋯O hydrogen bonds and π–π stacking are observed in 1. The 2D IR correlation spectroscopy was applied to study the molecular interactions induced by thermal perturbation. The emission spectra of 1 exhibit the characteristic transition of {sup 5}D{sub 0}→{sup 7}F{sub J}(J=0–4) of Eu(III). - Graphical abstract: Two isostructural 3D (3,8)-connected lanthanide arenedisulfonates were hydrothermally synthesized. The 2D IR correlation spectroscopy was applied to study the molecular interactions induced by thermal perturbation. Display Omitted - Highlights: • The first lanthanide arenedisulfonates incorporating fused-ring aromatic carboxylic acid. • Three-dimensional (3,8)-connected framework with tfz-d network topology. • The emission spectra of 1 exhibit the characteristic transition of {sup 5}D{sub 0}→{sup 7}F{sub J} (J=0–4) of Eu(III). • The 2D IR correlation spectroscopy was applied to study the molecular interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of Surface Alignment on Connectivity in Phosphonium-Containing Diblock Copolymer Anion-Exchange Membranes

The performance of ion-exchange membranes in fuel cells is critically linked to their ion-conducting morphology. In this report, we analyzed the connectivity of anion-exchange membranes (AEMs) by electrostatic force microscopy (EFM). As a tapping-mode AFM-based technique, EFM probes height, phase, and electrostatic force gradient through two-pass interleave scans, which reveals the direct relationship between membrane surface morphology and connectivity of the ionic domain. The AEMs are diblock copolymers of a polyisoprene (PIp) block and a polystyrenic block containing the phosphonium ion (P(R3P+)MS). Different alignments of cylinders were observed in the bulk and on the surface for AEMs with different ionexchange capacities (IECs) and preparation methods. The impacts of the cylinder alignment on the connectivity of the ionic domain were then investigated by EFM. For AEM 13 with IEC = 0.44 mmol/g and a hexagonal morphology, cylinders aligned parallel to the surface, which led to many disconnected regions observed throughout the membrane. In contrast, the perpendicularly aligned channels of AEM 16 with IEC = 0.87 mmol/g consisted only of a well-connected ionic phase throughout the membrane.

25 ENERGY STORAGE↗
DOE OSTI2024

Investigating Mountain Watershed Headwater‐To‐Groundwater Connections, Water Sources, and Storage Selection Behavior With Dynamic‐Flux Particle Tracking

Abstract Climate change will impact mountain watershed streamflow both directly—with changing precipitation amounts and variability—and indirectly—through temperature shifts altering snowpack, melt, and evapotranspiration. To understand how these complex processes will affect ecosystem functioning and water resources, we need tools to distinguish connections between water sources (rain/snowmelt), groundwater storage, and exit fluxes (streamflow/evapotranspiration), and to determine how these connections change seasonally and as climate shifts. Here, we develop novel watershed‐scale approaches to understand water source, storage, and exit flux connections using a dynamic‐flux particle tracking model (EcoSLIM) applied in California's Cosumnes Watershed, which connects the Sierra Nevada and Central Valley. This work develops new visualizations and applications to provide mechanistic understanding that underpins the interpretation of isotopic field data at watershed scales to distinguish sources, flow paths, residence times, and storage selection. In our simulations, streamflow comes primarily from snow‐derived water while evapotranspiration generally comes from rain. Most streamflow starts above 1,000 m while evapotranspiration is sourced relatively evenly across the watershed and is generally younger than streamflow. Modeled streamflow consists primarily of water sourced from precipitation in the previous 5 years but before the current water year, while ET consists primarily of water from precipitation in the current water year. ET, and to a lesser extent streamflow, are both younger than water in groundwater storage. However, snowmelt‐derived streamflow preferentially discharges older water from snow‐derived storage. Dynamic‐flux particle tracking and new approaches presented here enable novel model‐tracer comparisons in large‐scale watersheds to better understand watershed behavior in a changing climate.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Information Connections among Multiple Investors: Evolutionary Local Patterns Revealed by Motifs

The concept of motifs provides a fresh perspective for studying local patterns, which is useful for understanding the essence of a network structure. However, few previous studies have focused on the evolutionary characteristics of weighted motifs while further considering participants’ differences. We study how information connections differ among multiple investors. The evolutionary 10-year trend of weighted 3-motifs in China’s energy stock markets is explored for the networks of co-holding behaviors among shareholders, who are classified as companies, funds and individuals. Our works allow us to detect the preferential local patterns distributed among different agents as their fluctuate involvement in networks. We find that the diversity of shareholders contributes to the statistical significance of local patterns, while homophily always exist among individuals. Modules of information connections are stable among reserved investors, which is especially apparent among companies. Individuals prefer to keep their connections with companies and funds. Unsteady modules happen owing to strengthen links among funds during the time that they are main participants in stock markets. More details about multiple investors informationally connected in evolutionary local patterns can be detected by our work.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

The structure of locally bounded finite-dimensional representations of connected locally compact groups

An analogue of a Lie theorem is obtained for (not necessarily continuous) finite-dimensional representations of soluble finite-dimensional locally compact groups with connected quotient group by the centre. As a corollary, the following automatic continuity proposition is obtained for locally bounded finite-dimensional representations of connected locally compact groups: if G is a connected locally compact group, N is a compact normal subgroup of G such that the quotient group G/N is a Lie group, N{sub 0} is the connected identity component in N, H is the family of elements of G commuting with every element of N{sub 0}, and π is a (not necessarily continuous) locally bounded finite-dimensional representation of G, then π is continuous on the commutator subgroup of H (in the intrinsic topology of the smallest analytic subgroup of G containing this commutator subgroup). Bibliography: 23 titles. (paper)

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Global and Local Connectivities Describe Hydrogen Intercalation in Metal Oxides

We introduce global connectivity, Ω, which quantifies the detailed connectivity of a material and accurately captures reactivity behavior. Here, we demonstrate that combining global and local connectivity describes how metal oxides interact with hydrogen. Blending density functional theory, graph theory, and machine learning we built a reactivity model which accurately predicts hydrogen intercalation potentials of different metal oxides experimentally measured in the lab. The use of global connectivity can accelerate materials design through the development of novel structure-property relationships.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Experiments and Analyses of Data Transfers Over Wide-Area Dedicated Connections

Dedicated wide-area network connections are increasingly employed in high-performance computing and big data scenarios. One might expect the performance and dynamics of data transfers over such connections to be easy to analyze due to the lack of competing traffic. However, non-linear transport dynamics and end-system complexities (e.g., multi-core hosts and distributed filesystems) can in fact make analysis surprisingly challenging. We present extensive measurements of memory-to-memory and disk-to-disk file transfers over 10 Gbps physical and emulated connections with 0–366 ms round trip times (RTTs). For memory-to-memory transfers, profiles of both TCP and UDT throughput as a function of RTT show concave and convex regions; large buffer sizes and more parallel flows lead to wider concave regions, which are highly desirable. TCP and UDT both also display complex throughput dynamics, as indicated by their Poincare maps and Lyapunov exponents. For disk-to-disk transfers, we determine that high throughput can be achieved via a combination of parallel I/O threads, parallel network threads, and direct I/O mode. Our measurements also show that Lustre filesystems can be mounted over long-haul connections using LNet routers, although challenges remain in jointly optimizing file I/O and transport method parameters to achieve peak throughput.

Rao, Nageswara S.↗
DOE OSTI2023

Throughput Measurements and Capacity Estimates for Quantum Connections

The throughput of conventional and quantum network connections is an important performance metric, which is typically specified by bits per second (bps) and entangled quntum bits per second (ebps), respectively. It is measured over practical quantum network connections using specialized methods, and estimated using analytical bounds for which extensive theory has been developed. For practical connections, however, these two quantities have often been hard to correlate due to the lack of measurements and estimates derived under well-characterized common conditions. They both differ significantly from the conventional network throughput of TCP which employs buffers and loss recovery mechanisms. We describe a conventional-quantum testbed that enables the comparison of these two quantities both qualitatively and quantitatively. The bps and ebps throughput is measured over fiber connections of lengths over 75 kilometers, which show that the former decreases significantly slower with distance than the latter and in a qualitatively different way. The analytic capacity estimates of ebps are derived using approximations based on light intensity measurements, and they decrease more rapidly with distance than the measured ebps throughput. These results provide qualitative insights into the conventional transport mechanisms based on buffers, and the conditions used in deriving the analytical ebps capacity estimates.

Rao, Nageswara↗
DOE OSTI2023

Fuel Cell Stack Model for Real-Time Simulation of Grid-Connected Applications

Fuel cell stacks coupled with electrolyzers and hydrogen storage sites can be a promising category of distributed energy resources for both grid-connected and stand-alone power systems. However, because of high costs, at-scale hardware testing of fuel cell stacks for grid-connected applications is not economically viable at present. A model-based system that can accurately captures the steady-state and dynamic response of fuel cell stacks over long time periods (hours), is needed. This paper demonstrate a real-time electromagnetic transient model of a megawatt-scale, grid-connected proton exchange membrane fuel cell stack, coupled with a mass-based hydrogen storage system. This model can emulate the electrical steady-state and dynamic response of grid-connected fuel cell stacks. We validate the model using the response of commercial hardware fuel cell stacks and analytical models in the literature - using a digital real-time simulator (RSCAD). The proposed real-time model is then used to simulate cases spanning different time horizons and to design controller-hardware-in-the-loop experiments to evaluate controllers for hydrogen stations.

activation potential↗
DOE OSTI2024

Dispatching Grid-Forming Inverters in Grid-Connected and Islanded Mode

This paper explores the dispatchability of grid-forming (GFM) inverters in grid-connected and islanded mode. GFM inverters usually use droop control to automatically share power with other GFM sources (inverters and synchronous generators) and follow the change in the load demand; however, they can be dispatched like their grid-following (GFL) counterparts to output the target active and reactive power. This will help grid operators better manage their inverter-based resources (IBRs) to improve operation efficiency and reliability; therefore, this paper proposes an innovative concept of dispatching GFM sources (inverters and synchronous generators) to output the target power in both grid-connected and islanded mode by adjusting their droop intercepts. The fundamental principle is that the GFM inverter's active and reactive power is dictated by its frequency and voltage, and thus dispatching the active and reactve power of a GFM inverter can be achieved through dispatching its frequency and voltage. Moreover, the concept distinguishes the dispatch rules for grid-connected and islanded mode. Finally, the concept is validated with an example microgrid system with two GFM inverters, one diesel generator, one GFL inverter, and the load in both grid-connected and islanded mode. This pioneering work results in practical guidance for the development of energy management systems for future electric grids with GFM and GFL inverters.

dispatching↗
DOE OSTI2018

Reduced-Order Aggregate Model for Parallel-Connected Single-Phase Inverters

This paper outlines a reduced-order aggregate dynamical model for parallel-connected single-phase grid-connected inverters. For each inverter, we place no restrictions on the converter topology and merely assume that the ac-side switch-averaged voltage can be controlled via pulsewidth modulation. The ac output of each inverter interfaces through an LCL filter to the grid. The closed-loop system contains a phase locked loop for grid synchronization, and real- and reactive-power control are realized with inner and outer PI current- and power-control loops. We derive a necessary and sufficient set of parametric relationships to ensure that a reduced-order aggregated state-space model for an arbitrary number of such paralleled inverters has the same model order and structure as any single inverter. We also present reduced-order models for the settings where the real- and reactive-power setpoints are different and where the inverters have different power ratings. We anticipate the proposed model being useful in analyzing the dynamics of large collections of parallel-connected inverters with minimal computational complexity. The aggregate model is validated against measurements obtained from a multi-inverter experimental setup consisting of three 750-VA paralleled grid-connected inverters, hence establishing robustness of the analytical result to parametric variations seen in practice.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Evaluating Time Varying Connectivities and System Throughput in Opportunistic Networks for Smart Grid Applications

With increasing proliferation of smart phones, there is an opportunity to employ mobile ad hoc networks to connect to distributed energy assets located in remote areas. With embedded intelligence and edge computing capabilities, autonomous ‘edge control nodes’ can enable a decentralized energy nexus, without the need for on-demand communications. Authors have developed an opportunistic networking framework using Bluetooth Low Energy and a specialized mobile phone application that enables delay tolerant networking for the above framework. Here, this paper presents the analysis of time varying graph connectivity for such an opportunistic mobile ad hoc network. Dependence of connectivity on different network parameters such as radio characteristics, the mobility of data mules and parameters governing how connections are established are explored. Simulation results showing the variation of above trends have been presented.

Bluetooth↗
DOE OSTI2016

Determining fine-scale migratory connectivity and habitat selection for a migratory songbird by using new GPS technology

Migratory aerial insectivores are among the fastest declining avian group, but our understanding of these trends has been limited by poor knowledge of migratory connectivity and the identification of critical habitat across the vast distances they travel annually. Using new, archival GPS loggers, we tracked individual purple martins ( Progne subis ) from breeding colonies across North America to determine precise (<10m) locations of migratory and overwintering roost locations in South America and to test hypotheses for fine-scale migratory connectivity and habitat use. We discovered weak migratory connectivity at the roost scale, and extensive, fine-scale mixing of birds in the Amazon from distant (>2000 km) breeding sites, with some individuals sharing the same roosting trees. Despite vast tracts of contiguous forest in this region, birds occupied a much more limited habitat, with most (56%) roosts occurring on small habitat islands that were strongly associated with water. Only 17% of these roosts were in current protected areas. As a result, these data reflect a critical advance in our ability to remotely determine precise migratory connectivity and habitat selection across vast spatial scales, enhancing our understanding of population dynamics and enabling more effective conservation of species at risk.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Finding new friends and revisiting old ones – how plant lipid droplets connect with other subcellular structures

Summary The number of described contact sites between different subcellular compartments and structures in eukaryotic cells has increased dramatically in recent years and, as such, has substantially reinforced the well‐known premise that these kinds of connections are essential for overall cellular organization and the proper functioning of cellular metabolic and signaling pathways. Here, we discuss contact sites involving plant lipid droplets (LDs), including LD‐endoplasmic reticulum (ER) connections that mediate the biogenesis of new LDs at the ER, LD‐peroxisome connections, that facilitate the degradation of LD‐stored triacylglycerols (TAGs), and the more recently discovered LD‐plasma membrane connections, which involve at least three novel proteins, but have a yet unknown physiological function(s).

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-260: Development of a System to Verify for Connection Consistency in a Brachytherapy

Purpose: Brachytherapy has multiple manual procedures which are prone to human error, especially during the connection process of the treatment device to applicator. This is when considerable attention is required. In this study, we propose a new connection verification device concept. Methods: The system is composed of a ring magnet (anisotropic ferrite : magfine Inc), hole device (A1324LUA-T : Allegro MicroSystems Phil Inc) and an in-house check cable, which is made from magnetic material (Figure1). The magnetic field distribution is affected by the check cable position and any magnetic field variation is detected by the hole device. This system frequency is 20Hz and the average of 4 signals was used as hole device value to reduce noise. Results: The value of the hole device is altered, depending on the location of the check cable. The resolution of the check cable position is 5mm and 10mm, around a 10mm region from the hole device and over 10mm, respectively. There was a reduction in sensitivity of the hole device, in our test, which was linked to the distance of the hole device from the check cable. Conclusion: We demonstrated a new concept of connection verification in a brachytherapy. This system has the possibility to detect an incorrect connection. Moreover, the system is capable of self-optimization, such as determining the number of hole device and the magnet strength.Acknowledgement:This work was supported by JSPS Core -to-Core program Number 23003 and KAKENHI Grant Number 26860401. This work was supported by JSPS Core-to-Core program Number 23003 and KAKENHI Grant Number 26860401.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Use of Fiber Optic Distributed Acoustic Sensing for Measuring Hydraulic Connectivity for Geothermal Applications

Advanced methods in reservoir characterization are required to effectively harness geothermal energy from fractured high-temperature, high-pressure crystalline rock. It is critical to determine sufficient fluid connection between injection and production wells to enhance sweep efficiency and optimize the lifetime of the reservoir. A technology is needed that can monitor hydraulic connectivity in real time at any depth in the reservoir, throughout the lifetime of the reservoir. GeoMechanics Technologies, in collaboration with California State University, Long Beach (CSULB) and Silixa LLC, working in cooperation with the Department of Energy, Small Business Innovation Research through DOE SBIR Grant No: DE-SC-0017744, conducted a Phase I research project to investigate the use of fiber optic Distributed Acoustic Sensing (DAS) to improve geothermal reservoir characterization. Fiber optic DAS technology uses inter-well pressure sensing in response to periodic injection to determine hydraulic connectivity in fractured geothermal reservoirs. Fiber optic technology is capable of withstanding high temperatures and pressures typical of geothermal reservoirs. This tool would provide nearly continuous pressure monitoring along the length of the wellbore, providing knowledge into hydraulic pathways even where perforations do not exist. Real-time hydraulic monitoring can be performed without interrupting normal field operations. Also, measurements can be obtained throughout the lifetime of the well, ideally accounting for any changes in operations or reservoir configurations or thermally induced changes in permeability. The objective of this research effort was to develop and document an innovative tool that can be used for geothermal reservoir characterization. GeoMechanics Technologies and partners investigated and documented the use of fiber optic DAS for measuring the hydromechanical response caused by fractures in a reservoir and how that correlates to reservoir connectivity. For this Phase I project, numerical simulations, laboratory testing, and a field demonstration were performed to further validate the effectiveness of DAS technology for detecting formation hydraulics. This report summarizes the project activities. The main significant findings are: 1. From the numerical simulations using conceptual models, it is concluded that a high permeability zone inside a reservoir shows a different strain pattern along vertical monitoring lines away from the injection, when inducing low frequency pressure pulses. 2. The order of magnitude of strain observed at a distance of 100 ft from the injection well ranged from nanostrain to microstrain. Such strains are detectable with DAS tools currently available to industry. 3. Laboratory experiments stressed the importance of cable design and layout in the field, making calibration on site necessary for each application individually. 4. Field comparison highlighted the operational conditions that play a role in adding noise to the DAS measurement, where temperature effects for this type of application are also considered as noise to the strain measurements. 5. The analyses conducted to date provide motivation for further research, development and application of this technology, combined with field testing.

15 GEOTHERMAL ENERGY↗