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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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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Cs(BBr)6 by Materials Project

Cs(BBr)6 crystallizes in the trigonal R-3 space group. The structure is two-dimensional and consists of three Cs(BBr)6 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Cs sites. In the first Cs site, Cs is bonded to twelve Br atoms to form distorted edge-sharing CsBr12 cuboctahedra. There are a spread of Cs–Br bond distances ranging from 3.86–4.05 Å. In the second Cs site, Cs is bonded in a 9-coordinate geometry to six Br atoms. There are three shorter (3.80 Å) and three longer (3.86 Å) Cs–Br bond lengths. There are four inequivalent B sites. In the first B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.96 Å. In the second B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.97 Å. In the third B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.96 Å. In the fourth B site, B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.97 Å. There are four inequivalent Br sites. In the first Br site, Br is bonded in a distorted single-bond geometry to two Cs and one B atom. In the second Br site, Br is bonded in a single-bond geometry to two equivalent Cs and one B atom. In the third Br site, Br is bonded in a single-bond geometry to one Cs and one B atom. In the fourth Br site, Br is bonded in a single-bond geometry to one Cs and one B atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BBr by Materials Project

BBr crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of eighteen bromoborane molecules. B is bonded in a distorted single-bond geometry to one Br atom. The B–Br bond length is 1.93 Å. Br is bonded in a single-bond geometry to one B atom. The Br–B bond length is 1.93 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Experimental Study of TCP Throughput Profiles and Dynamics Over Dedicated Connections

A throughput profile expressed as a function of the round-trip times of a data transport infrastructure is a critical indicator of its level of optimization, particularly, over dedicated connections. We study the throughput profiles of eleven TCP versions using measurements collected over dedicated hardware-emulated connections with distances spanning round the earth. Among them, BBR has overall higher temporal variations and lower throughput profiles compared to five loss-based TCP versions, and the comparison with other TCP versions is mixed. Using the Poincare map regions of throughput time traces, we show that the richer dynamics of BBR are correlated with its lower throughput profiles. We present basic analytical results that indicate that higher temporal variations of TCP methods lead to lower throughput profiles, thereby establishing the underlying causality. Under external losses, BBR achieves sustained high throughput compared to others as the loss rate is increased. Overall, our results provide insights into the relationship between time dynamics and throughput profiles of TCP versions, in particular, show that limited time traces can be indicative of global properties of throughput profiles.

Rao, Nageswara↗
DOE OSTI2020

Materials Data on AgB11H6CBr6 by Materials Project

Ag(BBr)5B5CH6BBr crystallizes in the orthorhombic Pnma space group. The structure is one-dimensional and consists of four bromoborane molecules; four B5CH6 clusters; and two Ag(BBr)5 ribbons oriented in the (1, 0, 0) direction. In each B5CH6 cluster, there are three inequivalent B+0.27+ sites. In the first B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the second B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the third B+0.27+ site, B+0.27+ is bonded in a bent 120 degrees geometry to one C4- and one H1+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. C4- is bonded in a 1-coordinate geometry to five B+0.27+ and one H1+ atom. The C–H bond length is 1.08 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one B+0.27+ atom. In each Ag(BBr)5 ribbon, Ag1+ is bonded to six Br1- atoms to form corner-sharing AgBr6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Ag–Br bond distances ranging from 2.83–3.02 Å. There are three inequivalent B+0.27+ sites. In the first B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.98 Å. In the second B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.97 Å. In the third B+0.27+ site, B+0.27+ is bonded in a single-bond geometry to one Br1- atom. The B–Br bond length is 1.98 Å. There are three inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted single-bond geometry to two equivalent Ag1+ and one B+0.27+ atom. In the second Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Ag1+ and one B+0.27+ atom. In the third Br1- site, Br1- is bonded in a distorted L-shaped geometry to one Ag1+ and one B+0.27+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ultrathin Boron Growth onto Nanodiamond Surfaces via Electrophilic Boron Precursors

Diamond as a templating substrate is largely unexplored, and the unique properties of diamond, including its large bandgap, thermal conductance, and lack of cytotoxicity, makes it versatile in emergent technologies in medicine and quantum sensing. Surface termination of an inert diamond substrate and its chemical reactivity are key in generating new bonds for nucleation and growth of an overlayer material. Oxidized high-pressure high temperature (HPHT) nanodiamonds (NDs) are largely terminated by alcohols that act as nucleophiles to initiate covalent bond formation when an electrophilic reactant is available. In this work, we demonstrate a templated synthesis of ultrathin boron on ND surfaces using trigonal boron compounds. Boron trichloride (BCl 3 ), boron tribromide (BBr 3 ), and borane (BH 3 ) were found to react with ND substrates at room temperature in inert conditions. BBr 3 and BCl 3 were highly reactive with the diamond surface, and sheet-like structures were produced and verified with electron microscopy. Surface-sensitive spectroscopies were used to probe the molecular and atomic structure of the ND constructs’ surface, and quantification showed the boron shell was less than 1 nm thick after 1–24 h reactions. Observation of the reaction supports a self-terminating mechanism, similar to atomic layer deposition growth, and is likely due to the quenching of alcohols on the diamond surface. X-ray absorption spectroscopy revealed that boron-termination generated midgap electronic states that were originally predicted by density functional theory (DFT) several years ago. DFT also predicted a negative electron surface, which has yet to be confirmed experimentally here. The boron-diamond nanostructures were found to aggregate in dichloromethane and were dispersed in various solvents and characterized with dynamic light scattering for future cell imaging or cancer therapy applications using boron neutron capture therapy (BNCT). The unique templating mechanism based on nucleophilic alcohols and electrophilic trigonal precursors allows for covalent bond formation and will be of interest to researchers using diamond for quantum sensing, additive manufacturing, BNCT, and potentially as an electron emitter.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Dual Feedstock Upcycling of α-Methylstyrene-Doped Poly(methyl methacrylate) and Biomass via the Telescope of Depolymerization and Diels–Alder Reaction

Nearly 90% of poly(methyl methacrylate) (PMMA) is not recycled and instead ends up in landfills. Conventional pyrolysis of PMMA recovers impure methyl methacrylate (MMA) with low economic value. Here, we present a telescoped dual upcycling strategy that integrates PMMA depolymerization, Diels–Alder cycloaddition, and aromatization to convert AMS-doped PMMA and biomass-derived 2,5-dimethylfuran (DMF) into 1,2,4-trimethylbenzene (pseudocumene), a valuable chemical feedstock. BBr 3 proved effective in promoting the challenging Diels–Alder reaction between MMA and DMF under high pressure of argon.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Throughput Measurements and Profile Analysis of Cloud Networks

Cloud networks utilize virtual connections to connect virtual machines distributed across cloud sites. They are increasingly deployed due to flexible provisioning using software and cost-effectiveness in not requiring to build physical network infrastructure. However, their extensive virtualization makes it unclear how well the established practices of conventional networks translate to them. Here, we study throughput measurements over a Google Cloud network using a matching hardware emulated conventional network, which provide production and exploratory conditions, respectively. The measurements span connections representing local, cross-continental and around the Earth distances. We study the effects of parallel flows, congestion control algorithms and retransmissions on the network throughput profile expressed as a function of RTT. We compare the throughput profile of Google Cloud network with those of emulated network under various loss conditions, including those too disruptive or expensive in the former. Our analysis based on the concave-convex shape and utilization-concavity coefficients of throughput profiles indicates an overall agreement of performance between the two networks, thereby justifying the use of conventional network emulations to analyze cloud networks. In terms of practical use, our study establishes that BBR and BBRv2 alpha TCP achieve higher throughput compared to loss-based congestion control algorithms under most network configurations, especially, under losses at large RTT.

Phanekham, Derek [Southern Methodist Univ., Dallas↗
DOE OSTI2023

Elephants Sharing the Highway: Studying TCP Fairness in Large Transfers over High Throughput Links

Escalating bandwidth demand strains high-performance data networks, posing potential performance risks. TCP congestion control algorithms enhance reliability and optimize bandwidth usage. Network performance is influenced by factors such as AQM algorithms and router buffer size. In the context of constrained network resources, understanding how TCP flows share networks and the resulting performance impact is essential. This paper introduces insights into TCP fairness and performance involving a comparison of TCP CUBIC, Reno, Hamilton, and BBR versions 1 and 2 across real-world networks supporting high bandwidths of up to 25 Gbps. The research explores TCP behaviors with AQM algorithms like FIFO, FQ_CODEL, and RED, alongside diverse buffer sizes. Notably, findings reveal that manipulating buffers and queuing methods yields contrasting outcomes based on bandwidth. BBRv2 emerges as a superior fair algorithm, pivotal for swift transfers, particularly in scientific data scenarios. These results provide crucial guidance for future network design, ensuring equitable performance optimization.

Kiran, Mariam↗