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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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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Non-spectroscopic surface plasmon sensor with a tunable sensitivity

We demonstrate a non-spectroscopic surface plasmon sensor with a tunable sensitivity which is based on the relationship between the wave number of surface plasmon polaritons (SPPs) on metal film and the refractive index of the specimen in contact with the metal film. A change in the wave number of the SPPs results in a variation in the propagation angle of the leakage radiation of the SPPs. A reference light is used to interfere with the leakage radiation, and the refractive index of the specimen can be obtained by measuring the period of the interference fringes. The sensitivity of the sensor can be tuned by changing the incident direction of the reference light and this cannot be realized by conventional surface plasmon sensors. For a reference angle of 1.007°, the sensitivity and resolution of the sensor are 4629 μm/RIU (RIU stands for refractive index unit) and 3.6 × 10{sup −4} RIU, respectively. In addition, the sensor only needs a monochromatic light source, which simplifies the measurement setup and reduces the cost.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Variance-based sensitivity indices for stochastic models with correlated inputs

The goal of this article is the formulation of the principles of one of the possible strategies in implementing correlation between input random variables so as to be usable for algorithm development and the evaluation of Sobol’s sensitivity analysis. With regard to the types of stochastic computational models, which are commonly found in structural mechanics, an algorithm was designed for effective use in conjunction with Monte Carlo methods. Sensitivity indices are evaluated for all possible permutations of the decorrelation procedures for input parameters. The evaluation of Sobol’s sensitivity coefficients is illustrated on an example in which a computational model was used for the analysis of the resistance of a steel bar in tension with statistically dependent input geometric characteristics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Enhancing the pH sensitivity by laterally synergic modulation in dual-gate electric-double-layer transistors

The sensitivity of a standard ion-sensitive field-effect transistor is limited to be 59.2 mV/pH (Nernst limit) at room temperature. Here, a concept based on laterally synergic electric-double-layer (EDL) modulation is proposed in order to overcome the Nernst limit. Indium-zinc-oxide EDL transistors with two laterally coupled gates are fabricated, and the synergic modulation behaviors of the two asymmetric gates are investigated. A high sensitivity of ∼168 mV/pH is realized in the dual-gate operation mode. Laterally synergic modulation in oxide-based EDL transistors is interesting for high-performance bio-chemical sensors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Reconfigurable and ultra-sensitive in-line Mach-Zehnder interferometer based on the fusion of microfiber and microfluid

A reconfigurable Mach-Zenhnder interferometer (MZI) based on a microfluidic cavity (MFC) constructed by embedding a microfiber between two segments of single-mode fibers with pre-designed lateral offset has been proposed and experimentally demonstrated. The MFC serves as an interference arm with an eccentric annular cross section and allows convenient sample (gas or liquids) replacement procedure. The microfiber works as the other interference arm that provides the proposed device with ease of reconstruction and also enhances the force sensitivity. The re-configurability and the ultra-wide tuning sensitivity range are demonstrated by immersing the MZI constructed with a 484 μm-long-MFC and a microfiber 44 μm in diameter in different droplets. Ultrahigh sensitivities of 34.65 nm/°C (∼88 380 nm/RIU) and −493.7 nm/N (∼−590 pm/με) are experimentally achieved using a droplet with a refractive index of ∼1.44.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Sensitivity of optical mass sensor enhanced by optomechanical coupling

Optical mass sensors based on cavity optomechanics employ radiation pressure force to drive mechanical resonator whose mechanical susceptibility can be described by nonlinear optical transmission spectrum. In this paper, we present an optical mass sensor based on a two-cavity optomechanical system where the mechanical damping rate can be decreased by adjusting a pump power so that the mass sensitivity which depends on the mechanical quality factor has been enhanced greatly. Compared with that of an optical mass sensor based on single-cavity optomechanics, the mass sensitivity of the optical mass sensor is improved by three orders of magnitude. This is an approach to enhance the mass sensitivity by means of optomechanical coupling, which is suitable for all mass sensor based on cavity optomechanics. Finally, we illustrate the accurate measurement for the mass of a few chromosomes, which can be achieved based on the current experimental conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Multiple temperature effects on up-conversion fluorescences of Er{sup 3+}-Y b{sup 3+}-Mo{sup 6+} codoped TiO{sub 2} and high thermal sensitivity

We report multiple temperature effects on green and red up-conversion emissions in Er{sup 3+}-Y b{sup 3+}-Mo{sup 6+} codoped TiO{sub 2} phosphors. With increasing temperature, the decrease of the red emission from {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2}, the increase of green emission from {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} and another unchanged green emission from {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} were simultaneously observed, which are explained by steady-state rate equations analysis. Due to different evolution with temperature of the two green emissions, higher thermal sensitivity of optical thermal sensor was obtained based on the transitions with the largest fluorescence intensity ratio. Two parameters, maximum theoretical sensitivity (S{sub max}) and optimum operating temperature (T{sub max}) are given to describe thermal sensing properties of the produced sensors. The intensity ratio and energy difference ΔE of a pair of energy levels are two main factors for the sensitivity and accuracy of sensors, which should be referred to design sensors with optimized sensing properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Modeling and sensitivity analysis of mass transfer in active multilayer polymeric film for food applications

The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction in the permeability and oxygen transfer rate values. Scavenging capacity of the multilayer film increased linearly with the increase of the reactive layer thickness and the oxygen absorption reaction at short times decreased proportionally with the thickness of the external PET layer.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Synthesis and characterization of Allium cepa L. as photosensitizer of dye-sensitized solar cell

The synthesis and characterization of Allium cepa L. used as natural pigment for natural dye sensitizer of solar cell has successfully done and anthocyanin is extracted. Anthocynin is color pigment of plant which has characteristic absorption spectrum of photon and excites electrons up to pigment molecules. As the anthocyanin absorbed light increases the excited electrons increase as well. The generated current also increases and it leads to the efficiency increase. The energy conversion efficiency of the cells sensitized with dye of Allium cepa L. was 3,045 x 10{sup −4}%. A simple technique was taken to fabricate dye sensitizer solar cell is spincoating.

14 SOLAR ENERGY↗
DOE OSTI2016

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposite

TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I – V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Post-deposition annealing temperature dependence TiO{sub 2}-based EGFET pH sensor sensitivity

EGFET pH sensor is one type of pH sensor that is used to measure and determine pH of a solution. The sensing membrane of EGFET pH sensor plays vital role in the overall performance of the sensor. This paper studies the effects of different annealing temperature of the TiO{sub 2} sensing membranes towards sensitivity of EGFET pH sensor. Sol-gel spin coating was chosen as TiO{sub 2} deposition techniques since it is cost-effective and produces thin film with uniform thickness. Deposited TiO{sub 2} thin films were then annealed at different annealing temperatures and then were connected to the gate of MOSFET as a part of the EGFET pH sensor structure. The thin films now act as sensing membranes of the EGFET pH sensor and sensitivity of each sensing membrane towards pH was measured. From the results it was determined that sensing membrane annealed at 300 °C gave the highest sensitivity followed by sample annealed at 400 °C and 500 °C.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Improving the sensitivity of J coupling measurements in solids with application to disordered materials

It has been shown previously that for magic angle spinning (MAS) solid state NMR the refocused INADEQUATE spin-echo (REINE) experiment can usefully quantify scalar (J) couplings in disordered solids. This paper focuses on the two z filter components in the original REINE pulse sequence, and investigates by means of a product operator analysis and fits to density matrix simulations the effects that their removal has on the sensitivity of the experiment and on the accuracy of the extracted J couplings. The first z filter proves unnecessary in all the cases investigated here and removing it increases the sensitivity of the experiment by a factor ∼1.1–2.0. Furthermore, for systems with broad isotropic chemical shift distributions (namely whose full widths at half maximum are greater than 30 times the mean J coupling strength), the second z filter can also be removed, thus allowing whole-echo acquisition and providing an additional √2 gain in sensitivity. Considering both random and systematic errors in the values obtained, J couplings determined by fitting the intensity modulations of REINE experiments carry an uncertainty of 0.2–1.0 Hz (∼1−10 %).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Sensitivity of magnetic field-line pitch angle measurements to sawtooth events in tokamaks

The sensitivity of the pitch angle profiles measured by the motional Stark effect (MSE) diagnostic to the evolution of the safety factor, q, profiles during the tokamak sawtooth events has been investigated for Korea Superconducting Tokamak Advanced Research (KSTAR). An analytic relation between the tokamak pitch angle, γ, and q estimates that Δγ ∼ 0.1° is required for detecting Δq ∼ 0.05 near the magnetic axis (not at the magnetic axis, though). The pitch angle becomes less sensitive to the same Δq for the middle and outer regions of the plasma (Δγ ∼ 0.5°). At the magnetic axis, it is not straightforward to directly relate the γ sensitivity to Δq since the gradient of γ(R), where R is the major radius of the tokamak, is involved. Many of the MSE data obtained from the 2015 KSTAR campaign, when calibrated carefully, can meet these requirements with the time integration down to 10 ms. The analysis with the measured data shows that the pitch angle profiles and their gradients near the magnetic axis can resolve the change of the q profiles including the central safety factor, q{sub 0}, during the sawtooth events.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Novel method to control explosive shock sensitivity: A mesoscale study to understand the effect of thermally expandable microsphere (TEM) inclusions in high explosives (HE) microstructure

When the void content and/or void structure of a high explosive (HE) is altered by some means (i.e., bulk heating or mechanical damage), the shock initiation behavior of the material changes. The ability to precisely predict the change in shock sensitivity after an HE has undergone microstructural changes is a crucial capability in multi-scale reactive flow models. Here, we utilize thermally expandable microspheres (TEMs) as a dopant in a polymer bonded explosive (PBX) matrix to alter the shock initiation properties in a controlled fashion. Here, using a mesoscale modeling approach, we evaluated how a single TEM (before and after thermal expansion) behaves under shock compression, as well as how the matrix PBX in the direct vicinity of the TEM is affected. We first examined the effect of an unexpanded TEM in the explosive matrix and found that its presence does not significantly perturb the bulk flow and by extension will not affect bulk sensitivity. Next, we examined the effect of an expanded TEM and found that its presence significantly perturbs the flow via hydrodynamic jetting, which causes a secondary shock wave with a strength that exceeds that of the incident wave. Finally, we showed that this secondary shock interacts with the downstream porosity to ignite a larger fraction of the overall pore volume, commensurate with the secondary shock strength and the affected volume, increasing the global (bulk) shock sensitivity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

CONSTRAINING THE R-MODE SATURATION AMPLITUDE FROM A HYPOTHETICAL DETECTION OF R-MODE GRAVITATIONAL WAVES FROM A NEWBORN NEUTRON STAR: SENSITIVITY STUDY

This paper consists of two related parts: in the first part we derive an expression of the moment of inertia (MOI) of a neutron star as a function of observables from a hypothetical r-mode gravitational-wave detection. For a given r-mode detection we show how the value of the MOI of a neutron star constrains the equation of state (EOS) of the matter in the core of the neutron star. Subsequently, for each candidate EOS, we derive a possible value of the saturation amplitude, α, of the r-mode oscillations on the neutron star. Additionally, we argue that an r-mode detection will provide clues about the cooling rate mechanism of the neutron star. The above physics that can be derived from a hypothetical r-mode detection constitutes our motivation for the second part of the paper. In that part we present a detection strategy to efficiently search for r-modes in gravitational-wave data. R-mode signals were injected into simulated noise colored with the advanced LIGO (aLIGO) and Einstein Telescope (ET) sensitivity curves. The r-mode waveforms used are those predicted by early theories based on polytropic EOS neutron star matter. In our best case scenario (α of order 10{sup −1}), the maximum detection distance when using the aLIGO sensitivity curve is ∼1 Mpc (supernova event rate of 3–4 per century) while the maximum detection distance when using the ET sensitivity curve is ∼10 Mpc (supernova event rate of 1–2 per year)

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A realistic assessment of the CTA sensitivity to dark matter annihilation

We estimate the sensitivity of the upcoming CTA gamma-ray observatory to DM annihilation at the Galactic centre, improving on previous analyses in a number of significant ways. First, we perform a detailed analyses of all backgrounds, including diffuse astrophysical emission for the first time in a study of this type. Second, we present a statistical framework for including systematic errors and estimate the consequent degradation in sensitivity. These errors may come from e.g. event reconstruction, Monte Carlo determination of the effective area or uncertainty in atmospheric conditions. Third, we show that performing the analysis on a set of suitably optimised regions of interest makes it possible to partially compensate for the degradation in sensitivity caused by systematics and diffuse emission. To probe dark matter with the canonical thermal annihilation cross-section, CTA systematics like non-uniform variations in acceptance over a single field of view must be kept below the 0.3% level, unless the dark matter density rises more steeply in the centre of the Galaxy than predicted by a typical Navarro-Frenk-White or Einasto profile. For a contracted r{sup −1.3} profile, and systematics at the 1% level, CTA can probe annihilation to b b-bar at the canonical thermal level for dark matter masses between 100 GeV and 10 TeV.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Dark matter sensitivity of multi-ton liquid xenon detectors

We study the sensitivity of multi ton-scale time projection chambers using a liquid xenon target, e.g., the proposed DARWIN instrument, to spin-independent and spin-dependent WIMP-nucleon scattering interactions. Taking into account realistic backgrounds from the detector itself as well as from neutrinos, we examine the impact of exposure, energy threshold, background rejection efficiency and energy resolution on the dark matter sensitivity. With an exposure of 200 t × y and assuming detector parameters which have been already demonstrated experimentally, spin-independent cross sections as low as 2.5 × 10{sup −49} cm{sup 2} can be probed for WIMP masses around 40 GeV/c{sup 2}. Additional improvements in terms of background rejection and exposure will further increase the sensitivity, while the ultimate WIMP science reach will be limited by neutrinos scattering coherently off the xenon nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Forecasting sensitivity on tilt of power spectrum of primordial gravitational waves after Planck satellite

By taking into account the contamination of foreground radiations, we employ the Fisher matrix to forecast the future sensitivity on the tilt of power spectrum of primordial tensor perturbations for several ground-based (AdvACT, CLASS, Keck/BICEP3, Simons Array, SPT-3G), balloon-borne (EBEX, Spider) and satellite (CMBPol, COrE, LiteBIRD) experiments of B-mode polarizations. For the fiducial model n{sub t}=0, our results show that the satellite experiments give good sensitivity on the tensor tilt n{sub t} to the level σ{sub n{sub t}}∼<0.1 for r∼>2×10{sup −3}, while the ground-based and balloon-borne experiments give worse sensitivity. By considering the BICEP2/Keck Array and Planck (BKP) constraint on the tensor-to-scalar ratio r, we see that it is impossible for these experiments to test the consistency relation n{sub t}=−r/8 in the canonical single-field slow-roll inflation models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Dark matter substructure modelling and sensitivity of the Cherenkov Telescope Array to Galactic dark halos

Hierarchical structure formation leads to a clumpy distribution of dark matter in the Milky Way. These clumps are possible targets to search for dark matter annihilation with present and future γ-ray instruments. Many uncertainties exist on the clump distribution, leading to disputed conclusions about the expected number of detectable clumps and the ensuing limits that can be obtained from non-detection. In this paper, we use the CLUMPY code to simulate thousands of skymaps for several clump distributions. This allows us to statistically assess the typical properties (mass, distance, angular size, luminosity) of the detectable clumps. Varying parameters of the clump distributions allows us to identify the key quantities to which the number of detectable clumps is the most sensitive. Focusing our analysis on two extreme clump configurations, yet consistent with results from numerical simulations, we revisit and compare various calculations made for the Fermi -LAT instrument, in terms of number of dark clumps expected and the angular power spectrum for the Galactic signal. We then focus on the prospects of detecting dark clumps with the future CTA instrument, for which we make a detailed sensitivity analysis using open-source CTA software. Based on a realistic scenario for the foreseen CTA extragalactic survey, and accounting for a post-trial sensitivity in the survey, we show that we obtain competitive and complementary limits to those based on long observation of a single bright dwarf spheroidal galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗