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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Auditory performance in bald eagles and red-tailed hawks: a comparative study of hearing in diurnal raptors

Collision with wind turbines is a conservation concern for eagles with population abundance implications. The development of acoustic alerting technologies to deter eagles from entering hazardous air spaces is a potentially significant mitigation strategy to diminish associated morbidity and mortality risks. As a prelude to the engineering of deterrence technologies, auditory function was assessed in bald eagles (Haliaeetus leucocephalus), as well as in red tailed hawks (Buteo jamaicensis). Auditory brainstem responses (ABRs) to a comprehensive battery of clicks and tone bursts varying in level and frequency were acquired to evaluate response thresholds, as well as suprathreshold response characteristics of wave I of the ABR, which represents the compound potential of the VIII cranial nerve. Sensitivity curves exhibited an asymmetric convex shape similar to those of other avian species, response latencies decreased exponentially with increasing stimulus level and response amplitudes grew with level in an orderly manner. Both species were responsive to a frequency band at least 4 octaves wide, with a most sensitive frequency of 2 kHz, and a high frequency limit of approximately 5.7 kHz in bald eagles and 8 kHz in red tailed hawks. Here, findings reported here provide a framework within which acoustic alerting signals might be developed.

17 WIND ENERGY↗
DOE OSTI2017

Comparative Study of Novel Fluorescent Cyanine Nucleotides: Hybridization Analysis of Labeled PCR Products Using a Biochip

This study investigated the synthesis and substrate properties of Cy5-labeled dUTP derivatives with different substituents, linkers between the dye unit and pyrimidine heterocycle and fluorophore charges. Fluorescently labeled nucleoside triphosphates were studied as substrates using multiplex PCR with Taq and Vent (exo-) DNA polymerases, the typical representatives of the A and B polymerase families. The efficiency of nucleotide incorporation during PCR was assessed with a multi-parameter hybridization analysis using a diagnostic DNA microarray. The hybridization analysis indirectly estimates the incorporation efficiency of dye-labeled nucleotides in multiplex PCR. Our results demonstrated higher efficiencies of substrates with electrically neutral dyes than electropositive and electronegative Cy5 residues.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

A Comparative Study of Doum fiber and Shrimp Chitin Based Reinforced Low Density Polyethylene Biocomposites

The aim of this paper was to study the effects of reinforcing low density polyethylene (LDPE) by using bio-fillers (Doum cellulose or Shrimp chitin) on the mechanical properties. Both, Doum cellulose extracted frsom Doum leaves and Shrimp chitin extracted from shrimp co-products were compounded with LPDE without and with compatibilizer. The biocomposites were prepared by melt blending in a twin-screw extruder. Torsion and flexural tests were performed to investigate the impact of each reinforcement on the biocomposite mechanical properties. The SEM was carried out to study the filler/polymer interface adhesion. The present study has demonstrated that Doum fibers and shrimp chitin succeed in improving the mechanical properties of LPDE bio-composites. The results also showed that the use of maleic anhydride-grafted polyethylene as a compatibilizer improves filler adhesion/matrix and mechanical properties. This study exhibits that polyethylene composites based on Doum fibers or shrimp chitin can be used to replace the polyethylene materials in several fields like packaging and automotive industries.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Reuse of Selected Lignocellulosic and Processed Biomasses as Sustainable Sources for the Fabrication of Nanocellulose via Ni(II)-Catalyzed Hydrolysis Approach: A Comparative Study

This study investigates for the first time the feasibility of isolating nanocellulose from several selected feedstocks via a novel Ni(II)-hydrolysis process, including lignocellulosic biomasses (oil palm trunk, banana peel and coconut husk) and processed biomasses (newspaper, tissue paper and cotton linter), with an obtained gravimetric yield ranging from 59.6 to 86.2%. The isolation of nanocellulose products from these selected feedstocks was verified by the successive removal of most of their non-cellulosic components (lignin and hemicellulose) and cellulose amorphous regions, the increase in the crystallinity index and the nanoscale of the individual crystals. Most importantly, the resultant nanocellulose products rendered better thermal stability than that of corresponding original sources, which are highly potential to be utilized as the new renewable sources of reinforcement materials with potential applications in bio-nanocomposites and thermoplastics. Therefore, this work proves the viability of direct production of nanocellulose from a variety of cellulosic sources by using Ni(II)-based transition metal salt catalyst. The results suggested that the concept of waste to wealth could be well executed from the obtained nanocellulose, which are greatly potential for various industrial applications.

09 BIOMASS FUELS↗
DOE OSTI2018

Comparative Study of Xylan Extracted by Sodium and Potassium Hydroxides (NaOH and KOH) from Bagasse Pulp: Characterization and Morphological Properties

Xylan is the second most abundant polysaccharide and the predominant hemicellulose component of soda bagasse pulp. The present endeavor focuses on increasing the value addition to underutilized agro-industrial residue such as bagasse. For this purpose, xylan was isolated by two conventional alkali extraction methods i.e. NaOH and KOH. The recovery rate and sugar composition of different reaction times and alkali consumptions were monitored with advanced method such as High Performance Liquid Chromatography (HPLC). The Fourier Transform Infrared Spectroscopy (FTIR) and Wide Angle X-ray spectroscopy (WAXS) were respectively employed to characterize the functional groups and Crystallinity Index (CrI) changes during the extraction process. It was explored that highest xylan recovery rates were obtained with 6% of NaOH at 120 min and 6% KOH at 45 min. The xylan morphology via WAXS was found that its structure to be amorphous. HPLC results also showed KOH had higher effectiveness than NaOH in terms of extracted xylan purity. Highest XGRs (Xylose to Glucose Ratios) were also achieved by KOH processes. Hence, this study contributes to the adequate utilization of agricultural residues, with promising potential for applications in the production of certain novel materials and chemical conversion industries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

On the Role of Fermi Energy in Determining Properties of Superconductors: a Detailed Comparative Study of Two Elemental Superconductors (Sn and Pb), a Non-cuprate (MgB{sub 2}) and Three Cuprates (YBCO, Bi-2212 and Tl-2212)

Fermi energies (E{sub F}s) of high- T{sub c} superconductors (SCs) have of late been evincing considerable interest because they are believed to be the cause of their high T{sub c}s and gap structures. Since Bardeen-Cooper-Schrieffer (BCS) equations for elemental and generalized-BCS equations for non-elemental SCs are derived under the blanket of the assumption E{sub F}/ kθ > > 1 (k = Boltzmann constant, θ = Debye temperature), they cannot shed light on the E{sub F}s of these SCs. This fact leads us to address the gaps (Δ{sub 0}s) and T{sub c}s of both types of SCs via recently derived equations which incorporate E{sub F} as a variable. For the specification of the E{sub F} of any SC, we now need another of its properties. Choosing j{sub 0}, the critical current density of the SC at T = 0, and following an idea due to Pines, we present for both types of SCs new equations for j{sub 0} that depend solely on the following properties of the SC: E{sub F}, θ, gram-atomic volume, electronic specific heat constant and a dimensionless construct y=kθ√(2m∗)/P{sub 0}√(E{sub F}), where m* is the effective mass of superconducting electrons and P{sub 0} their critical momentum. Appeal to the experimental values of Δ{sub 0}, T{sub c} and j{sub 0} of any SC then not only leads to values of E{sub F}, m* and P{sub 0} but also provides plausible clues about how its j{sub 0}—and therefore T{sub c}—may be increased.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

A Comparative Study for Optimization of Sensitivity and Noise Levels in Race-Track Sensors

In this study, we have designed fluxgate sensors at race-track geometry which were used to measure DC or low-frequency magnetic fields. The type of core material and the number of core layers on the sensitivity and the noise level were specifically examined. We could achieve to get a sensitivity of 440 kV/T and a noise level of 56 pT/ √Hz at 1 Hz in a large dynamical range extending up to 1.5 Oe.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A Comparative Study of Physical Properties of Er and Yb Nanophase Ferrite for Industrial Application

Nano ferrites CuCr{sub 0.3}Er{sub 0.03}Fe{sub 1.67}O{sub 4} and CuCr{sub 0.3}Yb{sub 0.03}Fe{sub 1.67}O{sub 4} were synthesized using standard ceramic technique. X-ray diffraction (XRD) patterns confirmed that the samples had cubic spinel structures. The average crystallite sizes of Er and Yb samples were in the range of 104.2–100 nm. The morphology analyses using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) confirmed that the samples were in the nanoscale range. The compositional analyses using energy-dispersive x-ray (EDX) showed the atomic percentage (at.%) and weight percentage (wt%) of the investigated samples. The magnetic properties were carried out at room (300 K) and at low (100 K) temperatures magnetic hysteresis loop. The data showed that Er sample had higher saturation magnetization (M{sub s}) and lower coercivity (H{sub c}) than that of Yb sample suggesting that Er sample can be applied in magnetic applications. Moreover, Er sample had higher dielectric constant (ε’), dielectric loss (ε”) and dielectric loss tangent (tan δ) than that of Yb sample. However, Yb sample had higher resistivity than that of Er sample suggesting that Yb sample can be applied in electrical applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Comparative Study of Nano- and Bulk La{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Co{sub 0.5}O{sub 3} Perovskite: Structural, Magnetic, and Transport Properties

In this paper, we report a detailed study of the structural, magnetic, and electrical transport properties of nano- and bulk La{sub 0.5}Sr{sub 0.5}Ti{sub 0.5}Co{sub 0.5}O{sub 3} perovskite with the aim to study the effect of size reduction on resistivity and the antiferromagnetic spin order that is seen in the bulk samples of the cobaltites. Both the phases crystallize with orthorhombic structure in the Pbnm space group. Size reduction causes an increase in both the lattice parameters and unit cell volume. The M–H curve of nanosample shows appearance of hysteresis and gives a clear evidence of the formation of ferromagnetic (FM) moments while almost no RT-FM behavior was found for bulk sample. The resistivity of the nanocrystalline sample has been found to be much lower than that of the bulk sample in the entire temperature range of investigation which could be due to the formation of ferromagnetic moments in the nanocrystallites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Comparative Study of Magnetocaloric Effect in La{sub 0.67}Ca{sub 0.20}Sr{sub 0.13}MnO{sub 3} Manganite Prepared by Sol-Gel Method and Spark Plasma Sintering

The La{sub 0.67}Ca{sub 0.20}Sr{sub 0.13}MnO{sub 3} nanoparticles and bulks were prepared by using sol-gel method (SGM) and spark plasma sintering (SPS), respectively. The X-ray diffraction analysis indicates each sample crystal in a single rhombohedral perovskite structure (space group R 3-bar c). The Curie temperature is slightly improved and the phase transition is sharpened after processing with SPS. The enhancement of magnetocaloric effect (MCE) is also observed in the samples prepared by SPS. For a field change of 3 T, the maximum isothermal entropy change is improved by 32 and 117% when different sintering temperatures and sintering pressures are applied. The magnetic phase transition and MCE can be well described by the Landau theory. The present studies suggest that the perovskite bulks prepared by SPS could be useful for the application of magnetic refrigeration.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Comparative study of energy and footprint minimization limit for two types of graphene-assisted ring-shape modulators

In this paper, a numerical investigation has been performed on the limits of miniaturization for a graphene-assisted modulator considering two different configurations, in both cases the critical coupling condition representing the OFF state, and the transmission level of − 3 dB the ON state. In addition, the power consumption per bit of 100 fJ/bit was established as the cutoff parameter for both modulator configurations, as well as the minimum chemical potential for the ON state of 0.4 eV for the hybrid modulator. Considering the parameters aforementioned, our results showed that both configurations of modulators have great potential of miniaturization, high modulation speed and low power consumption.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Vibrational spectra and electronic structure of 11-vertex boron-containing clusters: a comparative study of [B{sub 11}H{sub 11}]{sup 2–}, [CB{sub 10}H{sub 11}]{sup –}, and C{sub 2}B{sub 9}H{sub 11}

Vibrational spectroscopy studies of 11-vertex boron-containing clusters [B{sub 11}H{sub 11}]{sup 2–}(1), [2-CB{sub 10}H{sub 11}]{sup –} (2), and 2,3-C{sub 2}B{sub 9}H{sub 11} (3) revealed two low-frequency large-amplitude modes in their spectra and, therefore, structural nonrigidity of these polyhedra in contrast to related 12-, 10-, and 6-vertex closo-clusters. The nonrigidity originates from specific features of the electron density distribution. According to calculations within the framework of the 'Atoms in Molecule' (AIM) theory, these polyhedra are characterized by the lack of many bond paths localized on corresponding edges, in particular, between boron atoms with coordination numbers of 6 and 5 (6k and 5k). Consequently, these polyhedra are composed of not only trigonal faces, i.e., formally do not have the closo-structure that was traditionally ascribed to them based on formal count of (2n + 2) valence electrons. According to calculations of three-center delocalization indices, the absence of bond paths is not equivalent to the lack of interaction between corresponding atoms since this interaction occurs through open three-center bonds. The mechanism and reasons for signal averaging observed in {sup 11}B NMR spectra of compounds 1 and 2 in contrast to 3 are analyzed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

A Comparative Study of the Microstructure, Mechanical Properties and Corrosion Resistance of Ni- or Fe- Based Composite Coatings by Laser Cladding

Ni- and Fe-based composite coatings were laser cladded on 40Cr steel to improve the surface mechanical property and corrosion resistance, respectively. The microstructure and phase composition were analyzed by x-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectrometer (EDS). The micro-hardness, tribological properties and electrochemical corrosion behavior of the coatings were evaluated. The results show that the thickness of both the coatings is around 0.7 mm, the Ni-based coating is mainly composed of γ-(Ni, Fe), FeNi{sub 3}, Ni{sub 31}Si{sub 12}, Ni{sub 3}B, CrB and Cr{sub 7}C{sub 3}, and the Fe-based coating is mainly composed of austenite and (Fe, Cr){sub 7}C{sub 3}. Micro-hardness of the Ni-based composite coating is about 960 HV{sub 0.3}, much higher than that of Fe-based coating (357.4 HV{sub 0.3}) and the 40Cr substrate (251 HV{sub 0.3}). Meanwhile, the Ni-based composite coating possesses better wear resistance than the Fe-based coating validated by the worn appearance and the wear loss. Electrochemical results suggested that Ni-based coating exhibited better corrosion resistance than the Fe-based coating. The 40Cr substrate could be well protected by the Ni-based coating.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Laser Desorption Ionization of As{sub 2}Ch{sub 3} (Ch = S, Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As{sub 2}Ch{sub 3} (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S{sub p}{sup +/–} and As{sub m}{sup +/–}) and 34 binary (As{sub m}S{sub p}{sup +/–}) species for As{sub 2}S{sub 3} glass, 2 unary (Se{sub q}{sup +/–}) and 26 binary (As{sub m}Se{sub q}{sup +/–}) species for As{sub 2}Se{sub 3} glass, 7 unary (Te{sub r}{sup +/–}) and 23 binary (As{sub m}Te{sub r}{sup +/–}) species for As{sub 2}Te{sub 3} material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Comparative Study of Flash and Acid Hydrolysis of Microalgae (Scenedesmus sp.) for the Recovery of Biochemicals and Production of Porous Biocarbon Nanosheets

An integrated biorefinery concept is a novel and economical process intensification methodology for efficient utilization of biomass components. In this research, microalgae (Scenedesmus sp.) slurry with biomass concentration of 8.5 wt.% was parallelly fractionated using two techniques: 'flash hydrolysis (FH)' and 'acid hydrolysis (AH)'. FH was performed at 240 degrees C with a residence time of 10 +/- 2 s in a continuous flow reactor, whereas AH was performed at 155 degrees C and reaction time of 15 min in a batch reactor. About 63% of microalgal biomass was solubilized in liquid hydrolysate through both FH and AH. However, AH had an advantage over FH in recovering microalgae proteins and carbohydrates. FAME recovery through solvent extraction from FH and AH derived wet solids (insoluble microalgae) was 40 and 63%, respectively. Finally, the FH- and AH-derived post extraction solid residue was thermally activated using K2CO3 to produce highly microporous biocarbon nanosheets with BET surface areas of 712 and 1289 m2 g-1, respectively. Overall, an integrated process was developed using two potential hydrolysis techniques to maximize utilization of microalgae components.

BASIC BIOLOGICAL SCIENCES,BIOMASS FUELS↗