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Chen, Yan

Publications and source records attributed to Chen, Yan.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

City Reach Code Technical Support Document

This report describes and analyzes a set of energy efficiency measures that will save 20% energy over ASHRAE Standard 90.1-2013. The measures will be used to formulate a Reach Code for cities aiming to go beyond national model energy codes. A coalition of U.S. cities together with other stakeholders wanted to facilitate the development of voluntary guidelines and standards that can be implemented in stages at the city level to improve building energy efficiency. The coalition's efforts are being supported by the U.S. Department of Energy via Pacific Northwest National Laboratory (PNNL) and in collaboration with the New Buildings Institute.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Heterologous Gene Expression of N -Terminally Truncated Variants of LipPks1 Suggests a Functionally Critical Structural Motif in the N -terminus of Modular Polyketide Synthase

Streptomyces genomes have a high G + C content and typically use an ATG or GTG codon to initiate protein synthesis. Although gene-finding tools perform well in low GC genomes, it is known that the accuracy in predicting a translational start site (TSS) is much less for high GC genomes. LipPks1 is a Streptomyces-derived, well-characterized modular polyketide synthase (PKS). Here, using this enzyme as a model, we experimentally investigated the effects of alternative TSSs using a heterologous host, Streptomyces venezuelae. One of the TSSs employed boosted the protein level by 59-fold and the product yield by 23-fold compared to the originally annotated start codon. Interestingly, a structural model of the PKS indicated the presence of a structural motif in the N-terminus, which may explain the observed different protein levels together with a proline and arginine-rich sequence that may inhibit translational initiation. Lastly, this structure was also found in six other modular PKSs that utilize noncarboxylated starter substrates, which may guide the selection of optimal TSSs in conjunction with start-codon prediction software.

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

A Combined Variable-Temperature Neutron Diffraction and Thermogravimetric Analysis Study on a Promising Oxygen Electrode, SrCo 0.9 Nb 0.1 O 3–δ , for Reversible Solid Oxide Fuel Cells

The present study reported herein investigates the temperature–structure–stoichiometry relationship of a promising oxygen electrode SrCo 0.9 Nb 0.1 O 3-δ over a temperature (T) range from room temperature (RT) to 900 °C. The techniques employed are variable-temperature neutron diffraction (VTND) and thermogravimetric analysis (TGA). At $T$ < 75 °C, VTND reveals a tetragonal (P4/mmm) structure with a G-type magnetic ordering. Above 75 °C, the nucleus structure remains the same, while the magnetic ordering disappears. A phase transition from tetragonal ($P4/mmm$) to cubic ($Pm\overline3m$) is observed at 412 °C, where the two Co sites and three O sites in the $P4/mmm$ phase converge to one equivalent site, respectively. The phase transition temperature coincides with the peak temperature of oxygen uptake obtained by TGA. It is also observed that the Nb dopant has no preferred Co site to occupy. The oxygen vacancies are mostly located at the O3 site surrounding the Co2 site in the $P4/mmm$ structure. The intermediate-spin state of Co 3+ at the Co2 site is responsible for the observed distortions of CoO 6 octahedra, i.e., elongation of Co2O 6 octahedra and shortening of Co1O 6 octahedra along the c-axis, which is a phenomenon known as Jahn–Teller distortion. At high temperatures, large thermal displacement factor for O 2– is observed with high concentration of oxygen vacancies, providing a structural environment favorable to high O 2– conductivity in Nb-doped SrCoO 3 -based oxygen electrode materials.

25 ENERGY STORAGE↗
DOE OSTI2017

Energy Savings Analysis: ANSI/ASHRAE/IES Standard 90.1-2016

To meet statutory requirements, DOE conducted an analysis to quantify the expected energy savings associated with Standard 90.1-2016. This report documents the methodology used to conduct the analysis. Based on the analysis, DOE has determined that the 2016 edition of the ANSI/ASHRAE/IES Standard 90.1 would improve overall energy efficiency in buildings subject to the code compared to the 2013 edition of Standard 90.1.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

High performance aluminum–cerium alloys for high-temperature applications

Light-weight high-temperature alloys are important to the transportation industry where weight, cost, and operating temperature are major factors in the design of energy efficient vehicles. Aluminum alloys fill this gap economically but lack high-temperature mechanical performance. Alloying aluminum with cerium creates a highly castable alloy, compatible with traditional aluminum alloy additions, that exhibits dramatically improved high-temperature performance. These compositions display a room temperature ultimate tensile strength of 400 MPa and yield strength of 320 MPa, with 80% mechanical property retention at 240 °C. A mechanism is identified that addresses the mechanical property stability of the Al-alloys to at least 300 °C and their microstructural stability to above 500 °C which may enable applications without the need for heat treatment. Lastly, neutron diffraction under load provides insight into the unusual mechanisms driving the mechanical strength.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

Towards a framework for selection of supervisory control for commercial buildings: HVAC system energy efficiency

This paper develops and utilizes an optimization based framework to investigate the maximal energy efficiency potentially attainable by HVAC system operation in a non-predictive context. Performance is evaluated relative to the existing state of the art set-point reset strategies. The expected efficiency increase driven by operation constraints relaxations is evaluated.

Ramachandran, Thiagarajan↗
DOE OSTI2017

A Systematic Classification for HVAC Systems and Components

Depending on the application, the complexity of an HVAC system can range from a small fan coil unit to a large centralized air conditioning system with primary and secondary distribution loops, and central plant components. Currently, the taxonomy of HVAC systems and the components has various aspects, which can get quite complex because of the various components and system configurations. For example, based on cooling and heating medium delivered to terminal units, systems can be classified as either air systems, water systems or air-water systems. In addition, some of the system names might be commonly used in a confusing manner, such as “unitary system” vs. “packaged system.” Without a systematic classification, these components and system terminology can be confusing to understand or differentiate from each other, and it creates ambiguity in communication, interpretation, and documentation. It is valuable to organize and classify HVAC systems and components so that they can be easily understood and used in a consistent manner. This paper aims to develop a systematic classification of HVAC systems and components. First, we summarize the HVAC component information and definitions based on published literature, such as ASHRAE handbooks, regulations, and rating standards. Then, we identify common HVAC system types and map them to the collected components in a meaningful way. Classification charts are generated and described based on the component information. Six main categories are identified for the HVAC components and equipment, i.e., heating and cooling production, heat extraction and rejection, air handling process, distribution system, terminal use, and stand-alone system. Components for each main category are further analyzed and classified in detail. More than fifty system names are identified and grouped based on their characteristics. The result from this paper will be helpful for education, communication, and systems and component documentation.

Li, Han↗
DOE OSTI2017

A robust and active hybrid catalyst for facile oxygen reduction in solid oxide fuel cells

The sluggish oxygen reduction reaction (ORR) greatly reduces the energy efficiency of solid oxide fuel cells (SOFCs). In this work, we present our results in dramatically enhancing the ORR kinetics and durability of the state-of-the-art La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode using a hybrid catalyst coating composed of a conformal PrNi 0.5 Mn 0.5 O 3 (PNM) thin film with exsoluted PrOx nanoparticles. At 750 °C, the hybrid catalyst-coated LSCF cathode shows a polarization resistance of ~0.022 Ω cm 2 , about 1/6 of that for a bare LSCF cathode (~0.134 Ω cm 2 ). Further, anode-supported cells with the hybrid catalyst-coated LSCF cathode demonstrate remarkable peak power densities (~1.21 W cm –2 ) while maintaining excellent durability (0.7 V for ~500 h). Near Ambient X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-Ray Absorption Fine Structure (NEXAFS) analyses, together with density functional theory (DFT) calculations, imply that the oxygen-vacancy-rich surfaces of the PrOx nanoparticles greatly accelerate the rate of electron transfer in the ORR whereas the thin PNM film facilitates rapid oxide-ion transport while drastically enhancing the surface stability of the LSCF electrode.

Chen, Yu↗
DOE OSTI2017

A study of stress-induced phase transformation and micromechanical behavior of CuZr-based alloy by in-situ neutron diffraction

The stress-induced phase transformation and micromechanical behavior of CuZr-based alloy were investigated by in-situ neutron diffraction. The pseudoelastic behavior with a pronounced strain-hardening effect is observed. The retained martensite nuclei and the residual stress obtained from the 1st cycle reduce the stress threshold for the martensitic transformation. A critical stress level is required for the reverse martensitic transformation from martensite to B2 phase. An increase of intensity for the B2 (110) plane in the 1st cycle is caused by the twinning along the {112}<111> twinning system. The convoluted stress partitioning influenced by the elastic and transformation anisotropy along with the newly formed martensite determines the microstress partitioning of the studied CuZr-based alloy. The reversible martensitic transformation is responsible for the pseudoelasticity. The macro mechanical behavior of the pure B2 phase can be divided into 3 stages, which are mediated by the evolvement of the martensitic transformation. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

36 MATERIALS SCIENCE↗
DOE OSTI2017

Shock-Driven Hydrodynamic Instability Growth Near Phase Boundaries and Material Property Transitions: Final Report

Activities for this grant included: 1) Development of dynamic impact experiments to probe strength and phase transition influence on dynamic deformation, 2) development of modern strength and phase aware simulation capabilities, 3) and post-processing of experimental data with simulation and closed form analytical techniques. Two different dynamic experiments were developed to probe material strengths in solid metals (largely copper and iron in this effort). In the first experiment a flyer plate impacts a flat target with an opposite rippled surface that is partially supported by a weaker window material. Post mortem analysis of the target sample showed a strong and repeatable residual plastic deformation dependence on grain orientation. Yield strengths for strain rates near 10 5 s -1 and plastic strains near ~50% were estimated to be around 180 to 240 MPa, varying in this range with grain orientation. Unfortunately dynamic real-time measurements were difficult with this setup due to diagnostic laser scattering; hence, an additional experimental setup was developed to complement these results. In the second set of experiments a rippled surface was ablated by a controlled laser pulsed, which launched a rippled shock front to an opposite initially flat diagnostic surface that was monitored in real-time with spatially resolved velocimetry techniques, e.g., line VISAR in addition to Transient Imaging Displacement Interferometry (TIDI) displacement measurements. This setup limited the displacements at the diagnostic surface to a reasonable level for TIDI measurements (~ less than one micrometer). These experiments coupled with analytical and numerical solutions provided evidence that viscous and elastic deviatoric strength affect shock front perturbation evolution in clearly different ways. Particularly, normalized shock front perturbation amplitudes evolve with viscosity (η) and perturbation wavelength (λ) as η/λ, such that increasing viscosity (or decreasing the initial wavelength) delays the perturbation decay. Conversely our experimental data, analysis and simulations show that for materials with elastic yield strength Y the normalized shock perturbation amplitude evolves with Yλ/A 0 , which shows wavelength increases have the opposite effect as in viscous materials and perturbation decay is also dependent on initial amplitude A 0 (viscous materials are independent of this parameter). Materials where strength had clear strain rate dependence, e.g., such as a PTW material law, behaved similarly to materials with only an effective yield stress (elastic-perfectly plastic) in the shock front perturbation studies obeying a Y eff λA 0 relationship where Y eff was a constant (near ~400 MPa for Cu for strain rates around 10 6 s -1 ). Magnitude changes in strain rate would increase Y eff as would be expected from the PTW behavior, but small perturbations (typical of regions behind the shock front) near a mean had little effect. Additional work based on simulations showed that phase transformation kinetics can affect the behavior of the perturbed shock front as well as the evolution of the RM-like instability that develops due to the imprint of the perturbed shock front on the initially flat surface as the shock breaks out.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structure evolution and thermoelectric properties of carbonized polydopamine thin films

Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. Finally, the largest room-temperature ZT of 2 × 10 –4 was obtained on samples heat-treated at 800 °C, which is higher than that of reduced graphene oxide.

36 MATERIALS SCIENCE↗
DOE OSTI2017

MiR-223 modulates hepatocellular carcinoma cell proliferation through promoting apoptosis via the Rab1-mediated mTOR activation

Hepatocellular carcinoma (HCC) is a common digestive malignancy. MiR-223, a well-identified miRNA, exhibits diverse properties in different cancers. In this study, we demonstrated that miR-223 could suppress cell growth and promote apoptosis in HepG2 and Bel-7402 HCC cell lines. We screened and identified a novel miR-223 target, Ras-related protein Rab-1(Rab1). Upregulation of miR-223 would specifically and markedly down-regulate Rab1 expression. In addition, miR-223-overexpressing subclones showed significant cell growth inhibition by increasing cell apoptosis in HepG2 and Bel-7402 cells. To identify the mechanisms, we firstly investigated the mTOR pathway and found that pmTOR, p70S6K and Bcl-2 were dramatically down-regulated after miR-223 transfection, while no changes in the level of Bax was visualized. Furthermore, our data showed that the anti-tumor effects arising from miR-223 transfection in HCC cells may be due to the deactivation of mTOR pathway caused by the suppression of Rab1 expression when miR-223 is overexpressed. In summary, our results indicate that miR-223 functions as a tumor suppressor and plays a critical role in inhibiting the tumorigenesis and promoting the apoptosis of HCC through the mTOR signaling pathway in vitro. By targeting Rab1, miR-223 efficiently mediates the mTOR pathway. Given these, miR-223 may be a potential therapeutic target for treating HCC. - Highlights: • miR-223 is downregulated in hepatocellular carcinomas. • Rab1 is a novel downstream target of miR-223. • miR-223 suppressed cell growth and enhanced apoptosis in HepG2 and Bel-7402 cells. • miR-223 modulated mTOR signaling pathway by targeting Rab1.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Non-congruence of high-temperature mechanical and structural behaviors of LaCoO 3 based perovskites

Our paper presents the mechanical behavior of LaCoO 3 and La 0.8 Ca 0.2 CoO3 ceramics under four-point bending in which the two cobaltites are subjected to a low stress of ~8 MPa at temperatures ranging from room temperature to 1000 °C. Unexpected stiffening is observed in pure LaCoO 3 in the 700–900 °C temperature range, leading to a significant increase in the measured Young’s modulus, whereas La 0.8 Ca 0.2 CoO 3 exhibits softening from 100 °C to 1000 °C, as expected for most materials upon heating. we use neutron diffraction, X-ray diffraction and micro-Raman spectroscopy to study the crystal structure of the two materials in the RT–1000 °C temperature range. Despite a detailed study, there is no conclusive evidence to explain the stiffening behavior observed in pure LaCoO 3 as opposed to the softening behavior in La 0.8 Ca 0.2 CoO 3 at high temperatures (above 500 °C).

36 MATERIALS SCIENCE↗
DOE OSTI2016

Improvement in synthesis of (K 0.5 Na 0.5 )NbO 3 powders by Ge 4+ acceptor doping

In this study, the effects of doping with GeO 2 on the synthesis temperature, phase structure and morphology of (K 0.5 Na 0.5 )NbO 3 (KNN) ceramic powders were studied using XRD and SEM. The results show that KNN powders with good crystallinity and compositional homogeneity can be obtained after calcination at up to 900°C for 2 h. Introducing 0.5 mol.% GeO 2 into the starting mixture improved the synthesis of the KNN powders and allowed the calcination temperature to be decreased to 800°C, which can be ascribed to the formation of the liquid phase during the synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Potential applications of industrial wireless technologies in the future HTR - 18505

High Temperature Reactor (HTR) is a kind of promising nuclear reactor for supplying electricity and heat with inherent safety. The High Temperature Reactor-Pebble bed Modular reactor (HTR-PM) in China is equipped with the Distributed Control System (DCS) where wired network is applied mainly based on fiber. Considering the difficulty and cost of implementation, the flexibility of network configuration and maintenance, the industrial wireless network might be potential for some cases in the network of the next generation of HTR. Nowadays, there are several technologies available for choice, such as wireless HART, WIA-PA and ZigBee. Characteristics of these technologies are introduced. The most important factors for choice of the technology of network are the required reliability and latency tolerance of communication. Analysis and classification of the communications needed in the network of the HTR are carried out, and a comparison of popular industrial wireless technologies, including the reliability, the latency, the communication distance, and the difficulty and cost of implementation is made. Generally speaking, considering the low latency, high reliability and the compatibility with HART devices, wireless HART is promising. WIA-PA could be applied if redundant gateway is required. ZigBee might show its advantages in power consumption and cost. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗