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Tian, Tian

Publications and source records attributed to Tian, Tian.

At least 19 records

FINETUNA: fine-tuning accelerated molecular simulations

Abstract Progress towards the energy breakthroughs needed to combat climate change can be significantly accelerated through the efficient simulation of atomistic systems. However, simulation techniques based on first principles, such as density functional theory (DFT), are limited in their practical use due to their high computational expense. Machine learning approaches have the potential to approximate DFT in a computationally efficient manner, which could dramatically increase the impact of computational simulations on real-world problems. However, they are limited by their accuracy and the cost of generating labeled data. Here, we present an online active learning framework for accelerating the simulation of atomic systems efficiently and accurately by incorporating prior physical information learned by large-scale pre-trained graph neural network models from the Open Catalyst Project. Accelerating these simulations enables useful data to be generated more cheaply, allowing better models to be trained and more atomistic systems to be screened. We also present a method of comparing local optimization techniques on the basis of both their speed and accuracy. Experiments on 30 benchmark adsorbate-catalyst systems show that our method of transfer learning to incorporate prior information from pre-trained models accelerates simulations by reducing the number of DFT calculations by 91%, while meeting an accuracy threshold of 0.02 eV 93% of the time. Finally, we demonstrate a technique for leveraging the interactive functionality built in to Vienna ab initio Simulation Package (VASP) to efficiently compute single point calculations within our online active learning framework without the significant startup costs. This allows VASP to work in tandem with our framework while requiring 75% fewer self-consistent cycles than conventional single point calculations. The online active learning implementation, and examples using the VASP interactive code, are available in the open source FINETUNA package on Github.

97 MATHEMATICS AND COMPUTING↗

Benchmarks of Global Clean Energy Manufacturing, 2014-2016

The Clean Energy Manufacturing Analysis Center (CEMAC), sponsored by the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE), provides objective analysis and up-to-date data on global supply chains and manufacturing of clean energy technologies. This updated version of the Benchmarks of Global Clean Energy Manufacturing sheds light on several fundamental questions about the global clean technology manufacturing enterprise: How does clean energy technology manufacturing impact national economies? What are the economic opportunities across the manufacturing supply chain? What are the global dynamics of clean energy technology manufacturing?

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Novel structured Sm 0.5 Sr 0.5 CoO 3-δ cathode for intermediate and low temperature solid oxide fuel cells

The performance of solid oxide fuel cell (SOFC) can be significantly enhanced using nanostructured cathode obtained by infiltration/impregnation method. However, this method has been limited due to multi-step preparation process and instability of the obtained nanoscale catalyst under long-term operation. We report here a simple, cost-effective and reproducible approach to fabricate nanostructured Sm 0.5 Sr 0.5 CoO 3-δ (SSC) cathode with enhanced performance and stability. The SSC powders were prepared by a freeze-drying method through a combustion route using Pluronic F-127 as the template. The SSC freeze-drying powders have unique morphology and a significant phase change at 750 °C. The oxygen non-stoichiometry (δ) of the SSC powders is 0.18 at room temperature, while the δ values are 0.66, 0.75 and 0.90 at 600 °C, 700 °C and 800 °C, respectively. The novel structured SSC cathode was prepared by screen-printing and one-step sintering process using the freeze-drying SSC powders. Maximum cell power densities of 0.83 and 1.13 W cm -2 are achieved at 550 °C and 600 °C, respectively for single cells with the novel structured SSC cathode. Moreover, single cells show excellent stability at 600 °C under a current density of 600 mA cm -2 over 250 h. This work expands opportunities to exploit nanotechnology in a wide range of intermediate and low temperature energy conversion devices.

25 ENERGY STORAGE↗

Effect of non-solvent from the phase inversion method on the morphology and performance of the anode supported microtubular solid oxide fuel cells

The microstructure of the anode in anode-supported solid oxide fuel cells has significant influence on the cell performance. Here, microtubular Ni-yttria stabilized zircona (Zr 0.8 Y 0.2 O 2 , YSZ) anode support has been prepared by the phase inversion method. Different compositions of non-solvent have been used for the fabrication of the Ni-YSZ anode support, and the correlation between non-solvent composition and characteristics of the microstructure of the anode support has been investigated. The presence of ethanol or isopropanol in the non-solvent can inhibit the growth of the finger-like pores in the anode support. With the increase of the concentration of ethanol or isopropanol in the non-solvent, a thin dense layer can be observed on the top of the prepared tubular anode support. In addition, the mechanism of pore formation is explained based on the inter-diffusivity between the solvent and the non-solvent. Lastly, the prepared microtubular solid oxide fuel cells (MT-SOFCs) have been tested, and the influence of the anode microstructure on the cell electrochemical performance is analyzed based on a polarization model.

36 MATERIALS SCIENCE↗

Redirecting Metabolic Flux via Combinatorial Multiplex CRISPRi-Mediated Repression for Isopentenol Production in Escherichia coli

CRISPR interference (CRISPRi) via target guide RNA (gRNA) arrays and a deactivated Cas9 (dCas9) protein has been shown to simultaneously repress expression of multiple genomic DNA loci. By knocking down endogenous genes in competing pathways, CRISPRi technology can be utilized to redirect metabolic flux toward target metabolite. In this study, we constructed a CRISPRi-mediated multiplex repression system to silence transcription of several endogenous genes to increase precursor availability in a heterologous isopentenol biosynthesis pathway. To identify genomic knockdown targets in competing pathways, we first designed a single-gRNA library with 15 individual targets, where 3 gRNA cassettes targeting gene asnA, prpE, and gldA increased isopentenol titer by 18-24%. We then combined the 3 single-gRNA cassettes into a two- or three-gRNA array and observed up to 98% enhancement in production by fine-tuning the repression level through titrating dCas9 expression. Our strategy shows that multiplex combinatorial knockdown of competing genes using CRISPRi can increase production of the target metabolite, while the repression level needs to be adjusted to balance the metabolic network and achieve the maximum titer improvement.

59 BASIC BIOLOGICAL SCIENCES↗

2017 Renewable Energy Data Book

The Renewable Energy Data Book for 2017 provides facts and figures on renewable energy deployment in the United States, with context of U.S. and global energy trends. Facts include renewable electricity capacity, generation, and capacity additions for U.S. and global electricity and energy as a whole, and for specific renewable electricity generation technologies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

2017 Offshore Wind Technologies Market Update

The 2017 Offshore Wind Technologies Market Update was developed by NREL for DOE's Office of Energy Efficiency and Renewable Energy, Wind Energy Technologies Office. This update complements the biennial Offshore Wind Technologies Market Report(Musial et al. 2017), which includes a more detailed discussion of the key trends and statistics included in this update. This work provides decision-makers, regulators, developers, financiers, and supply chain participants with quantitative information about the offshore wind market, technology, and cost status worldwide and in the United States.

17 WIND ENERGY↗

Effects of Microwave-Assisted Annealing on the Structure and Magnetic Properties of (Nd{sub 0.75}Pr{sub 0.25}){sub 9}Fe{sub 72}Ti{sub 1}Zr{sub 3}Mn{sub x} Mo{sub 4−x}B{sub 10.5}C{sub 0.5} Amorphous Ribbons

The amorphous as-spun ribbons with nominal composition (Nd{sub 0.75}Pr{sub 0.25}){sub 9}Fe{sub 72}Ti{sub 1}Zr{sub 3}Mn{sub x}Mo{sub 4−x}B{sub 10.5}C{sub 0.5}(x = 1, 2, 3) were annealed by microwave-assisted annealing. The effects of the Mn-doped alloys on glass-forming ability (GFA), crystallization, and magnetic properties of the Nd{sub 2}Fe{sub 14}B/α-Fe nanocomposite magnets were examined by thermal differential scanning calorimetry (DSC), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). An appropriate amount of Mn was beneficial to the optimization of the structure and magnetic properties. Compared with conventional annealing, the microwave-assisted annealing has contributed to the precipitation of hard magnetic phases and adjusted the proportion of hard and soft magnetic phases. The optimum magnetic properties with coercivity up to 805 kA/m were found for ribbons (with composition x = 1) annealed under the microwave power of 2000 W for 10 min.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Exploring New Models for Utility Distributed Energy Resource Planning and Integration: SMUD and Con Edison

As a result of the rapid growth of renewable energy in the United States, the U.S. electric grid is undergoing a monumental shift away from its historical status quo. These changes are occurring at both the centralized and local levels and have been driven by a number of different factors, including large declines in renewable energy costs, federal and state incentives and mandates, and advances in the underlying technology. Higher levels of variable-generation renewable energy, however, may require new and increasingly complex methods for utilities to operate and maintain the grid while also attempting to limit the costly build-out of supporting grid infrastructure.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

2016 Renewable Energy Data Book

The Renewable Energy Data Book for 2016 provides facts and figures on renewable energy deployment in the United States, with context of U.S. and global energy trends. Facts include renewable electricity capacity, generation, and capacity additions for U.S. and global electricity and energy as a whole, and for specific renewable electricity generation technologies.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

2016 Renewable Energy Data Book

The 2016 Renewable Energy Data Book provides facts and figures on energy and electricity use, renewable electricity in the United States, global renewable energy development, wind power, solar power, geothermal power, biopower, hydropower, marine and hydrokinetic power, hydrogen, renewable fuels, and clean energy investment.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Autonomous control of metabolic state by a quorum sensing (QS)-mediated regulator for bisabolene production in engineered E. coli

Inducible gene expression systems are widely used in microbial host strains for protein and commodity chemical production because of their extensive characterization and ease of use. However, some of these systems have disadvantages such as leaky expression, lack of dynamic control, and the prohibitively high costs of inducers associated with large-scale production. Quorum sensing (QS) systems in bacteria control gene expression in response to population density, and the LuxI/R system from Vibrio fischeri is a well-studied example. A QS system could be ideal for biofuel production strains as it is self-regulated and does not require the addition of inducer compounds, which reduce operational costs for inducer. In this study, a QS system was developed for inducer-free production of the biofuel compound bisabolene from engineered E. coli. Seven variants of the Sensor plasmid, which carry the luxI-luxR genes, and four variants of the Response plasmid, which carry bisabolene producing pathway genes under the control of the P luxI promoter, were designed for optimization of bisabolene production. Furthermore, a chromosome-integrated QS strain was engineered with the best combination of Sensor and Response plasmid and produced bisabolene at a titer of 1.1 g/L without addition of external inducers. This is a 44% improvement from our previous inducible system. The QS strain also displayed higher homogeneity in gene expression and isoprenoid production compared to an inducible-system strain.

09 BIOMASS FUELS↗

Evolving Distributed Generation Support Mechanisms: Case Studies from United States, Germany, United Kingdom, and Australia (Chinese translation)

This is the Chinese translation of NREL/TP-6A20-67613. This report expands on a previous National Renewable Energy Laboratory (NREL) technical report (Lowder et al. 2015) that focused on the United States' unique approach to distributed generation photovoltaics (DGPV) support policies and business models. While the focus of that report was largely historical (i.e., detailing the policies and market developments that led to the growth of DGPV in the United States), this report looks forward, narrating recent changes to laws and regulations as well as the ongoing dialogues over how to incorporate distributed generation (DG) resources onto the electric grid. This report also broadens the scope of Lowder et al. (2015) to include additional countries and technologies. DGPV and storage are the principal technologies under consideration (owing to market readiness and deployment volumes), but the report also contemplates any generation resource that is (1) on the customer side of the meter, (2) used to, at least partly, offset a host's energy consumption, and/or (3) potentially available to provide grid support (e.g., through peak shaving and load shifting, ancillary services, and other means).

14 SOLAR ENERGY↗