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Chen, Yan

Publications and source records attributed to Chen, Yan.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Time and frequency dependent mechanical properties of LaCoO 3 -based perovskites: Neutron diffraction and domain mobility

The study of domain wall movement and texture formation in ferroelastic LaCoO 3 perovskite under constant applied compressive stress has been performed using in situ neutron diffraction. Additionally, it was established that under constant applied compressive stress the domain walls show mobility that may lead both to the shrinkage (creep strain) and to the expansion (negative creep strain) of LaCoO 3 perovskite. The domain wall movement and texture formation can be explained by the availability, mobility, and interaction of twins, stacking faults, antiphase boundaries, dislocations, and point defects, such as oxygen vacancies and their complexes as well as impurity atoms. Lastly, the equation of motion was used to describe the possible mechanisms of domain wall movement under applied stress, and it was determined that the available solutions of this equation allow both for the shrinkage (creep strain) and for the expansion (negative creep strain) of LaCoO 3 perovskite to occur.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The relationship between Aquaporin-2 protein levels in amniotic fluid and the fetal kidney in humans

Aquaporin-2 (AQP2) is an important water channel protein that is expressed in the renal collecting duct and plays a key role in urine concentration and body water homeostasis. It has been demonstrated that the urinary excretion of AQP2 correlates strongly with its expression in the kidney in adult humans and rats. However, there have been no studies on the urinary excretion of AQP2 in human fetuses during development. Fetal urine is the main source of the amniotic fluid; we speculate that the level of AQP2 in the amniotic fluid could reflect the expression level of the AQP2 protein in the fetal kidney. The purpose of the present study was to explore the relationship between AQP2 in the amniotic fluid and that in the fetal kidney.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Anti-Galling Effects of α-Zirconium Phosphate Nanoparticles as Grease Additives

Grease plays important roles in reducing frictional loss and providing protection of rubbing surfaces. In this research, we investigated the effects of α -zirconium phosphate nanoparticles as additives in grease on the galling behavior of a pair of steels (4130 against P530). The results showed that the addition of 0.5 wt% of nanoparticles in petroleum jelly could reduce the friction for 10% and the area being galled for 80%. In terms of particle sizes, the 1 μ m sized particles have profound influence in galling reduction. This is due to the increased contribution of van der Waals forces in the stacked layers of those particles. Under shear, those particles are exfoliated, resulting in low friction and more surface coverage to protect surfaces from galling.

Engineering↗
DOE OSTI2018

Optimal Energy Consumption Forecast for Grid Responsive Buildings: A Sensitivity Analysis

It is envisioned that building systems will become active participants in the smart grid operation by controlling their energy consumption to optimize complex criteria beyond ensuring local end-use comfort satisfaction. A forecast of the building energy consumption will be necessary to enable integration between building and grid operation. Such forecast will be affected by parametric and measurement uncertainty. In this paper we develop a methodology for quantifying the sensitivity of optimal hourly energy consumption forecasts to various sources model and measurement uncertainty. We demonstrate the approach for a building heating ventilation and air conditioning (HVAC) system use-case.

Kundu, Soumya↗
DOE OSTI2018

Revealing the Structural Stability and Na-Ion Mobility of 3D Superionic Conductor Na 3 SbS 4 at Extremely Low Temperatures

All-solid-state batteries that employ superionic solid conductor potentially enable the broadening of battery operation in harsh environments, such as under subzero temperatures and even lower. The solid electrolyte as the key component requires structural stability, high-efficiency of ion transportation channels, and low activation energy to maintain the fast-ionic conduction against temperature drop. Herein, we use 3D superionic conductor Na 3 SbS 4 as a model to investigate the structure and conductive mechanism at extremely low temperature. Cryogenic in situ neutron and X-ray diffractions reveal that Na 3 SbS 4 maintains a stable tetragonal crystal structure and the anisotropic lattice contraction upon cooling. The dimensions of the S-gate (represented by the S–S pair length) that Na ions hop through in the 3D transportation network is found to maintain open sizes in the xy -plane, contributing to the low activation energy and impressive ionic conductivity. The Na-ion transportation network is demonstrated to be directionally accessible at the extremely low temperature, which reveals the ion conductive mechanism at broadened temperature range in the view of structure. Furthermore, these findings provide valuable guidance in the search for materials as promising solid electrolyte in solid-state batteries to fulfill harsh environmental needs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improving the Electrocatalytic Activity and Durability of the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ Cathode by Surface Modification

Electrode materials with high activity and good stability are essential for commercialization of energy conversion systems such as solid oxide fuel cells or electrolysis cells at the intermediate temperature. Modifying the existing perovskite-based electrode surface to form a heterostructure has been widely applied for the rational design of novel electrodes with high performance. Despite many successful developments in enhancing electrode performance by surface modification, some controversial results are also reported in the literature and the mechanisms are still not well understood. In this work, the mechanism of how surface modification impacts the oxygen reduction reaction (ORR) activity and stability of perovskite-based oxides was investigated. We took La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) as the thin-film model system and modified its surface with additive Pr x Ce 1–x O 2 layers of different thicknesses. We found a strong correlation between surface oxygen defects and the ORR activity of the heterostructure. By inducing higher oxygen vacancy concentration compared to bare LSCF, PrO 2 coating is proved to greatly facilitate the rate of oxygen dissociation, thus significantly enhancing the ORR activity. Because of low oxygen vacancy density introduced by Pr 0.2 Ce 0.8 O 2 and CeO 2 coating, on the one hand, it does not boost the rate of ORR but successfully suppresses surface Sr segregation, leading to an enhanced durability. Our findings will demonstrate the vital role of surface oxygen defects and provide important insights for the rational design of high-performance electrode materials through surface defect engineering.

25 ENERGY STORAGE↗
DOE OSTI2018

Connected Lighting Systems Efficiency Study: PoE Cable Energy Losses, Part 2

This is the second report of an investigation into energy losses in Ethernet cables used between Power over Ethernet (PoE) switches and luminaires in PoE connected lighting systems. Testing for Part 2 of the study was conducted in DOE’s Connected Lighting Test Bed in July and August 2018 and was a continuation of Part 1 studies conducted there in September 2017.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

A Control-oriented Building Envelope and HVAC System Simulation Model for a Typical Large Office Building

To enable advanced controls research for buildings, in this paper we present a dynamic simulation model for a typical large office building. In this model, we utilized EnergyPlus for calculating the building thermal load and the Modelica HVAC equipment library to implement the dynamic behavior of the heating, ventilation, and air conditioning (HVAC) system. We utilized a functional mockup interface to enable the run-time communication between the EnergyPlus model and the Modelica model. This simulation model can be driven by control inputs from supervisory decision making algorithms and thus can be used as a virtual testbed for advanced controls development and evaluation. To demonstrate the usage of the model, we implemented two HVAC control sequences representative for large office buildings, both based on the ASHRAE standard. Simulation results allowed us to compare the energy performance associated with the two control strategies, and the evolution of the system dynamics at a high temporal granularity.

Huang, Sen↗
DOE OSTI2018

A SIMULATION BASED APPROACH TO IMPACT ASSESSMENT OF PHYSICAL FAULTS: LARGE COMMERCIAL BUILDING HVAC CASE STUDY

We develop a simulation-based approach to fault impact analysis for a single duct VAV system, and analyze the dynamic and steady-state impact of equipment physical faults on building operation. The simulation model, a virtual testbed, can capture physical faults in the HVAC system of a large commercial building. The model can be utilized for generating data that can then be analyzed to quantify the impact of single or multiple faults. We illustrate the implementation of three physical faults: supply air temperature sensor bias, outdoor air temperature sensor bias, and cooling coil valve stuck. We simulate each fault with several fault intensity levels and at different seasonal operating conditions. Then, we analyze the impact of the above-mentioned faults using the metrics. The results show that the impact of a given physical fault depends on implemented control logic sequence and the seasonal operating conditions.

Chen, Yan↗
DOE OSTI2018

Understanding Structure–Activity Relationships in Sr 1– x Y x CoO 3–δ through in Situ Neutron Diffraction and Electrochemical Measurements

In this study, we report a systematic study on temperature-dependent local structural evolution, oxygen stoichiometry, and electrochemical properties of an oxygen-deficient perovskite Sr 0.7 Y 0.3 CoO 3–δ (SYC30) for oxygen electrocatalysis. The obtained results are then closely compared with its analogue Sr 0.9 Y 0.1 CoO 3–δ (SYC10) of different crystal structures to establish structure–activity relationships. The comparison shows that both SYC30 and SYC10 consist of alternate layers of oxygen-deficient Co1-polyhedra and oxygen-saturated Co2-octahedra with Co1-polyhedra being responsible for V o •• migration. It is also found that the distribution and concentration of oxygen vacancies within the Co1-layer are, respectively, less symmetrical and lower in SYC30 than those in SYC10, making the former unfavorable for oxygen transport. A molecular orbital energy analysis reveals that the energy gap between Fermi level and O 2p level in the active Co1-polyhedra is larger in SYC30 than that in SYC10, further suggesting that SYC10 is a better oxide-ion conductor and thus a better electrocatalyst for oxygen reduction reaction, which is unambiguously confirmed by the subsequent electrochemical measurements.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The LncRNA MALAT1 regulates CD80 transcription via the NF-κB signaling pathway in the A549 cell line

CD80 has been known to be a co-stimulatory factor expressed in antigen presenting cells (APCs) involved in T-cell activation. It can be expressed in non-bone marrow-derived cells induced by lipopolysaccharide (LPS) or other stimulators, and directly involved in the pathogenesis following T cell activation. However, the intricate transcription mechanisms that underlying the upregulation of CD80 expression levels in LPS-activated non-bone marrow-derived cells is still unknown. LncRNAs are confirmed to be involved in transcriptional regulation by influencing transcription factors. Therefore, we wanted to determine whether the lncRNA MALAT1, which has been found to be related to LPS-induced inflammation, could regulate the transcription of CD80. Our results showed that CD80 was upregulated in low-dose LPS-activated A549 cells in a NF-κB-dependent manner. The lncRNA MALAT1 can interfere with NF-κB activation and disrupt its binding efficiency with the CD80 promoter. Thus, the lncRNA MALAT1 can regulate CD80 transcription via the NF-κB signaling pathway in the LPS-activated A549 cell line.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Damage Precursor Assessment in Aerospace Structural Materials

The focus of this study was to apply a robust inspection technique for monitoring damage nucleation and propagation in 7075 aluminum alloy specimens exposed to cyclic loading. A previously developed specimen, linearly tapered in width along the length, was subjected to a sinusoidal tension-tension load while conductivity and strain were measured in-situ. Ex-situ measurements of modulus, hardness, surface potential, digital image correlation strain field, and neutron diffraction were made as a function of fatigue cycles. It is hypothesized that varying levels of induced stress along the length due to equal-force but varying area along the length will create a record of damage which can be probed to intuit a temporal history for the specimen. Baseline, intermediate, and failure sensor measurements for several specimens were compared and analyzed as a function of applied stress (varied linearly along the length) and fatigue cycles (constant). Mechanisms of damage nucleation and propagation due to fatigue cycling are discussed with an emphasis on which inspection methods are most promising for improving structural durability and state monitoring.

Cole, Daniel↗
DOE OSTI2018

Connected Lighting Systems Efficiency Study: PoE Cable Energy Losses, Part 2

Power over Ethernet (PoE) technology offers the ability to provide both low-voltage direct current (DC) power and communication over a standard Ethernet cable—also referred to as a local area network (LAN) cable or Category cable. Light-emitting diode (LED) technology has reduced the power required for lighting applications, while advances in PoE standards and technology have yielded substantial increases in the amount of power that can be delivered to a networked device over a single cable. As a result, PoE technology is emerging in lighting and many other applications beyond its historical foothold in telephony and networking equipment. Several major LED luminaire manufacturers have introduced PoE connected lighting systems in recent years, making this a potentially disruptive technology. PoE lighting systems can offer improved efficiency relative to traditional line voltage alternating current (AC) systems, because AC-DC power conversion losses can be reduced if this work is consolidated among one or more PoE switches, rather than being distributed among a greater number of smaller LED drivers. However, this effect can be offset to some extent by increased losses associated with an increased voltage drop in the low-voltage Ethernet cabling. In fact, these losses could exceed 15% in poorly designed systems. Aspects of cable design that can affect cable energy performance include American Wire Gauge (AWG), Category (e.g., 5e), shielding, and fire rating (e.g., CMP). Installation practices (e.g., bending, bundling, conduit) can also affect cable performance. Although cable energy losses can be predicted with knowledge of conductor DC resistance (DCR), and DCR can be estimated based on rated AWG, most product datasheets state maximum DCR - or reference standards that specify DCR limits - in lieu of nominal DCR.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Connected Lighting Systems Efficiency Study: PoE Cable Energy Losses, Part 2

DOE published a report in November 2017 (herein referred to as “Part 1”) summarizing the results of an exploratory study investigating power losses in Ethernet cables used between PoE switches and luminaires in PoE connected lighting systems. Testing was conducted at the Pacific Northwest National Laboratory (PNNL) Connected Lighting Test Bed (CLTB) in September 2017. The results were analyzed to explore the impact of cable selection on PoE lighting system energy efficiency, as well as the effectiveness of guidelines published by the American National Standards Institute (ANSI) C137 Lighting Systems Committee in 2017. The guidance offered in ANSI C137.3-2017 was found to be effective in limiting cable energy losses to 5% in PoE lighting applications, provided that the average cable length on a project does not exceed 50 m. This Part 2 report summarizes the results of a continued investigation of the power losses in Ethernet cables used between PoE switches and luminaires in PoE connected lighting systems. Testing was conducted at the PNNL CLTB in July-August 2018. A test setup comprising a PoE switch, a set of luminaires, and a reference meter was again used to test multiple cable models of varying design. The results were analyzed to explore the impact of cable selection and installation practices (e.g., cable bending, cable bundling, and installation in conduit) on PoE lighting system energy efficiency, as well as the effectiveness of the ANSI C137.3 guidelines. Notably, three cables—two of which were shielded—were previously excluded from the Part 1 study due to compatibility issues. All three cables were included in this Part 2 study, along with a fourth model cable introduced in Part 2. In addition, whereas no patch cords were used in Part 1, patch cords were used in some Part 2 testing. The ANSI C137.3 guidance was again shown to effectively limit power losses to less than 5% in the cables tested (varying in AWG, Category, shielding, fire rating, and manufacturer), and AWG again proved to be the most important cable design variable for energy performance, as expected. However, these findings should not be construed as being representative of all cable models and installation practices. For example, energy losses would be greater when cables are connected to patch cords, bundled in conduit, and loaded with powered devices (PDs) approaching 100 W input power. The other key finding was that with 44 W luminaires as PDs and room ambient temperatures below 30°C, cable energy losses were not substantially increased by cable bending or bundling in uninsulated conduit. However, environments with higher ambient temperatures will have greater energy losses due to increased conductor DCR. In addition, product selection and installation practices will have increased importance as PDs approaching 100 W input power—conveyed by a single Ethernet cable—are introduced following publication of the forthcoming Institute of Electrical and Electronics Engineers (IEEE) Standard 802.3bt. The report also provides recommendations and next steps, which include plans for additional PoE cable energy losses testing with higher-power PDs to more fully explore the potential of PoE lighting systems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Tracing Phase Transformation and Lattice Evolution in a TRIP Sheet Steel under High-Temperature Annealing by Real-Time In Situ Neutron Diffraction

Real-time in situ neutron diffraction was used to characterize the crystal structure evolution in a transformation-induced plasticity (TRIP) sheet steel during annealing up to 1000 °C and then cooling to 60 °C. Based on the results of full-pattern Rietveld refinement, critical temperature regions were determined in which the transformations of retained austenite to ferrite and ferrite to high-temperature austenite during heating and the transformation of austenite to ferrite during cooling occurred, respectively. The phase-specific lattice variation with temperature was further analyzed to comprehensively understand the role of carbon diffusion in accordance with phase transformation, which also shed light on the determination of internal stress in retained austenite. These results prove the technique of real-time in situ neutron diffraction as a powerful tool for heat treatment design of novel metallic materials.

Yu, Dunji↗
DOE OSTI2018

Lattice distortion in a strong and ductile refractory high-entropy alloy

Here, the maximization of the mixing entropy with the optimal range of enthalpy in high-entropy alloys (HEAs) can promote the formation of a stable single solid-solution phase with the absence of competing intermetallic compounds. The resultant effects, such as lattice distortion, can contribute to excellent mechanical properties, which has motivated numerous efforts to develop and design single-phase HEAs. However, challenges still remain, particularly on quantifying the lattice distortion and relating it to materials properties. In this study, we have developed a NbTaTiV refractory HEA with a single body-centered-cubic (BCC) structure using an integrated experimental and theoretical approach. The theoretical efforts include thermodynamic modeling, i.e., CALculation of PHAse Diagram (CALPHAD). The microstructural evolutions have been investigated by systematic heat-treatment processes. The typical dendrite microstructure was observed, which is caused by the elemental segregation during the solidification in the as-cast condition. The structural inhomogeneity and chemical segregation were completely eliminated by the proper homogenization treatment at 1200 °C for 3 days. The homogeneous elemental distribution was quantitatively verified by the Atom Probe Tomography (APT) technique. Importantly, results indicate that this HEA exhibits the high yield strength and ductility at both room and high temperatures (up to 900 °C). Furthermore, the effects of the high mixing entropy on the mechanical properties are discussed and quantified in terms of lattice distortions and interatomic interactions of the NbTaTiV HEA via first-principles calculations. It is found that the local severe lattice distortions are induced, due to the atomic interactions and atomic-size mismatch in the homogenization-treated NbTaTiV refractory HEA.

36 MATERIALS SCIENCE↗