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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca(GeIr)2 by Materials Project

Ca(IrGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Ca–Ir bond lengths are 3.35 Å. All Ca–Ge bond lengths are 3.24 Å. Ir is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.61 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeIr by Materials Project

IrGe is Modderite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ir is bonded to six equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing IrGe6 octahedra. The corner-sharing octahedra tilt angles range from 46–56°. There are a spread of Ir–Ge bond distances ranging from 2.51–2.62 Å. Ge is bonded in a 6-coordinate geometry to six equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(GeIr)2 by Materials Project

UIr2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All U–Ir bond lengths are 3.33 Å. All U–Ge bond lengths are 3.17 Å. Ir is bonded to four equivalent U and four equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing IrU4Ge4 tetrahedra. All Ir–Ge bond lengths are 2.48 Å. Ge is bonded in a 9-coordinate geometry to four equivalent U, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(GeIr)2 by Materials Project

CeIr2Ge2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ce is bonded in a 12-coordinate geometry to eight Ir and eight Ge atoms. There are four shorter (3.24 Å) and four longer (3.38 Å) Ce–Ir bond lengths. There are four shorter (3.27 Å) and four longer (3.28 Å) Ce–Ge bond lengths. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.52 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Ce and five Ge atoms. There are one shorter (2.45 Å) and four longer (2.50 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Ce and five Ir atoms. In the second Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Ce and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GeIr)2 by Materials Project

Eu(IrGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Eu–Ir bond lengths are 3.38 Å. All Eu–Ge bond lengths are 3.26 Å. Ir is bonded to four equivalent Eu and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing IrEu4Ge4 tetrahedra. All Ir–Ge bond lengths are 2.48 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Eu, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(GeIr)2 by Materials Project

SrIr2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Sr–Ir bond lengths are 3.44 Å. All Sr–Ge bond lengths are 3.31 Å. Ir is bonded to four equivalent Sr and four equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing IrSr4Ge4 tetrahedra. All Ir–Ge bond lengths are 2.49 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Sr, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(GeIr)2 by Materials Project

Sm(IrGe)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Sm is bonded in a 12-coordinate geometry to eight Ir and eight Ge atoms. There are four shorter (3.23 Å) and four longer (3.37 Å) Sm–Ir bond lengths. All Sm–Ge bond lengths are 3.27 Å. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 4-coordinate geometry to four equivalent Sm and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.51 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to four equivalent Sm and five Ge atoms. There are one shorter (2.44 Å) and four longer (2.50 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Sm and four equivalent Ir atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Sm and five Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaLa(GeIr)4 by Materials Project

CaLa(IrGe)4 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Ca–Ir bond lengths are 3.38 Å. All Ca–Ge bond lengths are 3.25 Å. La is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All La–Ir bond lengths are 3.38 Å. All La–Ge bond lengths are 3.27 Å. Ir is bonded to two equivalent Ca, two equivalent La, and four Ge atoms to form a mixture of distorted edge, corner, and face-sharing IrCa2La2Ge4 tetrahedra. There are two shorter (2.48 Å) and two longer (2.50 Å) Ir–Ge bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.60 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent La, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.68 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on EuIn2(GeIr)4 by Materials Project

EuIn2(IrGe)4 crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to four equivalent Ir, four equivalent In, and eight equivalent Ge atoms. All Eu–Ir bond lengths are 3.51 Å. All Eu–In bond lengths are 3.51 Å. There are four shorter (3.25 Å) and four longer (3.58 Å) Eu–Ge bond lengths. Ir is bonded in a 6-coordinate geometry to one Eu, two equivalent In, and four equivalent Ge atoms. Both Ir–In bond lengths are 2.79 Å. There are a spread of Ir–Ge bond distances ranging from 2.40–2.63 Å. In is bonded in a 10-coordinate geometry to two equivalent Eu, four equivalent Ir, and four equivalent Ge atoms. All In–Ge bond lengths are 3.09 Å. Ge is bonded in a 5-coordinate geometry to two equivalent Eu, four equivalent Ir, and two equivalent In atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca3(GeIr)4 by Materials Project

Ca3(IrGe)4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to four equivalent Ir and four equivalent Ge atoms. All Ca–Ir bond lengths are 3.15 Å. All Ca–Ge bond lengths are 3.14 Å. Ir is bonded in a 7-coordinate geometry to three equivalent Ca and four equivalent Ge atoms. There are one shorter (2.37 Å) and three longer (2.53 Å) Ir–Ge bond lengths. Ge is bonded in a 7-coordinate geometry to three equivalent Ca and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Beyond the Global Brain Differences: Intraindividual Variability Differences in 1q21.1 Distal and 15q11.2 BP1-BP2 Deletion Carriers

Carriers of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants exhibit regional and global brain differences compared with noncarriers. However, interpreting regional differences is challenging if a global difference drives the regional brain differences. Intraindividual variability measures can be used to test for regional differences beyond global differences in brain structure. Magnetic resonance imaging data were used to obtain regional brain values for 1q21.1 distal deletion (n = 30) and duplication (n = 27) and 15q11.2 BP1-BP2 deletion (n = 170) and duplication (n = 243) carriers and matched noncarriers (n = 2350). Regional intra-deviation scores, i.e., the standardized difference between an individual’s regional difference and global difference, were used to test for regional differences that diverge from the global difference. For the 1q21.1 distal deletion carriers, cortical surface area for regions in the medial visual cortex, posterior cingulate, and temporal pole differed less and regions in the prefrontal and superior temporal cortex differed more than the global difference in cortical surface area. For the 15q11.2 BP1-BP2 deletion carriers, cortical thickness in regions in the medial visual cortex, auditory cortex, and temporal pole differed less and the prefrontal and somatosensory cortex differed more than the global difference in cortical thickness. We find evidence for regional effects beyond differences in global brain measures in 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants. The results provide new insight into brain profiling of the 1q21.1 distal and 15q11.2 BP1-BP2 copy number variants, with the potential to increase understanding of the mechanisms involved in altered neurodevelopment.

15q11.2 BP1-BP2↗
DOE OSTI2025

Experimental investigation of flow distribution in enhanced geothermal systems with deep eutectic solvent

Geothermal energy has been recognized as a valuable alternative to fossil fuels and nuclear power, as it is renewable and reliable. Enhanced Geothermal Systems (EGSs) have the potential to expand geothermal energy production by enabling access to previously untapped geothermal resources. Geothermal short-circuiting poses a significant challenge to EGS development, leading to reduced heat extraction. Deep Eutectic Solvent (DES) exhibits favorable thermal and rheological properties, making it a candidate for geothermal applications. Here, this paper examines Choline Chloride-Based Deep Eutectic Solvent (DES) as a working fluid in geothermal applications and its potential to mitigate geothermal short-circuiting. Hydraulic experiments using a dual fracture flow loop were conducted at high temperatures. The results showed that DES exhibited higher differential pressure behavior compared to water. Flow distribution results revealed that DES enhances flow allocation within the small fracture, particularly when a temperature difference exists between fractures. Specifically, DES increased flow distribution by an average of 11% when the temperature difference was 85°C, and by 13% when the difference was 45°C, relative to water. These findings suggest that DES responds to thermal fracture differences, making it a potential remedy to address geothermal short-circuiting.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

Basal Melting and Oceanic Observations Beneath Central Fimbulisen, East Antarctica

Abstract Basal melting of ice shelves is fundamental to Antarctic ice sheet mass loss, yet direct observations remain sparse. We present the first year‐round melt record (2017–2021) from a phase‐sensitive radar on Fimbulisen, one of the fastest flowing ice shelves in Dronning Maud Land, East Antarctica. The observed long‐term mean ablation rate at 350 m depth below the central ice shelf was 1.0 ± 0.5 m yr −1 , marked by substantial sub‐weekly variability ranging from 0.4 to 3.5 m yr −1 . 36‐h filtered basal melt rate fluctuations closely align with ocean velocity. On seasonal time scales, melt rates peak during austral spring to autumn (September–March), driven by both elevated ocean velocities and thermal driving near the base. The combined effect of thermal driving and current speed explains the majority of the melt rate variability ( r = 0.84), highlighting the dominant role of shear‐driven turbulence. This relationship enables parameterization of melt rates for the decade‐long ocean record (2010–2021), although deviations appear under low and high forcing conditions. Both observed and parameterized melt rates show similar yearly mean magnitudes compared to satellite‐derived melt rates but with a tenfold lower seasonal amplitude and a 3‐month delay in seasonality. These detailed concurrent ice–ocean observations provide essential validation data for remote sensing and numerical models that aim to quantify and project ice‐shelf response to a change in ocean forcing. In situ measurements and continued monitoring are crucial for accurately assessing and modeling future basal melt rates, and for understanding the complex dynamics driving ice‐shelf stability and sea‐level change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Asynchronous quadratic control for constrained hidden markov jump linear systems with incomplete MTPM and MOCPM

Abstract This paper investigates the quadratic optimal control problem for constrained Markov jump linear systems with incomplete mode transition probability matrix (MTPM). Considering original system mode is not accessible, observed mode is utilized for asynchronous controller design where mode observation conditional probability matrix (MOCPM), which characterizes the emission between original modes and observed modes is assumed to be partially known. An LMI optimization problem is formulated for such constrained hidden Markov jump linear systems with incomplete MTPM and MOCPM. Based on this, a feasible state-feedback controller can be designed with the application of free-connection weighting matrix method. The desired controller, dependent on observed mode, is an asynchronous one which can minimize the upper bound of quadratic cost and satisfy restrictions on system states and control variables. Furthermore, clustering observation where observed modes recast into several clusters, is explored for simplifying the computational complexity. Numerical examples are provided to illustrate the validity.

Zhu, Jin↗
DOE OSTI2020

Laboratory Drilling Test Data of PDC bits with Sierra White Granite Rock

This file contains unprocessed drilling data tests on Sierra White Granite (SWG) using two new PDC bits. The tests were conducted at Sandia National Laboratories (SNL) in the Hard Rock Drilling Facility (HRDF). The collected data includes ROP data at rotational speeds of 80, 120, and 160 RPMs, with incremental weight on bit (WOB) up to 5100 lbs. The diameter of the 4-bladed and 5-bladed PDC bits was 3 3/4" and supplied by National Oilwell Varco (NOV). Five tests modes were conducted for both bits, which are as follow: (1) Rigid configuration, with no vibration compliance (2) Flywheel configuration (3) Torsional compliance configuration (4) Axial Compliance configuration (5) Combined Axial and Torsional compliance configuration Note: the WOB and torque in the drilling data should be calibrated by zeroing the WOB and torque when the drill bit tags the rock sample.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

Hard Rock Drilling Optimization Software

The main objective of the developed software is to reduce the cost per foot during drilling, in other words, optimize the drilling operational parameters in achieving optimum ROP while avoiding critical operational parameters due to either low ROP, drillstring vibration, accelerated cutter wear, or low MSE. The developed software can also be used for post-well analysis to provide insight and lessons learned for future drilling operations. Several functions are available in the software to help the user perform drilling analysis, optimization, and simulation.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

A Stochastic Covariance Shrinkage Approach in Ensemble Transform Kalman Filtering

The Ensemble Kalman Filters (EnKF) employ a Monte-Carlo approach to represent covariance information, and are affected by sampling errors in operational settings where the number of model realizations is much smaller than the model state dimension. To alleviate the effects of these errors EnKF relies on model-specific heuristics such as covariance localization, which takes advantage of the spatial locality of correlations among the model variables. This work proposes an approach to alleviate sampling errors that utilizes a locally averaged-in-time dynamics of the model, described in terms of a climatological covariance of the dynamical system. We use this covariance as the target matrix in covariance shrinkage methods, and develop a stochastic covariance shrinkage approach where synthetic ensemble members are drawn to enrich both the ensemble subspace and the ensemble transformation. We additionally provide for a way in which this methodology can be localized similar to the state-of-the-art LETKF method, and that for a certain model setup, our methodology significantly outperforms it.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Real-Time Drilling Optimization System for Improved Overall Rate of Penetration and Reduced Cost Per Foot in Geothermal Drilling

The key to success in geothermal drilling is economic feasibility, and a major cost in the development of geothermal resources is the actual drilling of the wells. In this project, a real-time drilling optimization system for geothermal drilling was developed. The system couples three individual components while drilling. The first component is a drill stem vibration analysis model, the second is Mechanical Specific Energy (MSE) analyses, and the third is a detailed PDC Rate of Penetration (ROP) drill bit model for optimum RPM and WOB combinations. The benefit of the coupled system is that the range of WOB and RPM could be selected to avoid drill stem vibrations. Secondly, MSE is used as an efficiency measure and the detailed PDC drill bit model ensures the drill bit does not endure temperatures that exceed the temperature at which the PDC cutters experience accelerated wear. The new detailed PDC bit model is based on rock/bit interaction that physically tracks the PDC cutter wear flats as the bit drills ahead giving the capability to calculate the temperature being generated underneath the worn cutters to better advise on operational parameters to avoid accelerated cutter wear and failure and to ensure that operational parameters are applied so that overall ROP is maximized. By combining the drill stem vibrations and the detailed PDC bit cutter wear and “safe” non-accelerated cutter wear temperature and optimum ranges of operating parameters, it results in higher ROP and lower cost drilling. Single cutter PDC testing performed in different lithologies at Sandia was utilized to verify the PDC cutter forces and depth of cut for new and worn cutters. Based on single cutter PDC temperature modeling, verification using single cutter data from the testing done by National Oilwell Varco (NOV) was performed. Sandia’s Hard-Rock Drilling Facility (HRDF) was utilized to test different drill bit configurations with different cutter designs and wear status with different induced modes of vibration to obtain the critical bit RPM/WOB ranges resulting in ineffective drilling and low ROP. The collected test data were further used to verify and calibrate the full hole PDC ROP model that was developed based on single cutter interaction data. A full coupled drill stem vibration model was formulated and verified with geothermal field data from the Chocolate Mountain Aerial Gunnery Range (CMAGR). A graphical user interface (GUI) was developed using Tkinter library in the computer programming language Python, which integrates all the developed models in one system. The developed system consists mainly of the PDC ROP model, PDC bit wear model, PDC cutter temperature model, Mechanical Specific Energy (MSE) model, and drillstring vibration model integrated into one system. The developed system can be used for both, post well analysis and real-time optimization using different criteria such as ROP maximization or MSE minimization. The software uses Differential Evolution Algorithm (DEA) to find optimum values for operational parameters based on last foot drilled while avoiding the drillstring vibration and cutter temperature critical operating parameters.

15 GEOTHERMAL ENERGY↗