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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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

On the analytical modeling of the nonlinear vibrations of pretensioned space structures

Pretensioned structures are receiving considerable attention as candidate large space structures. A typical example is a hoop-column antenna. The large number of preloaded members requires efficient analytical methods for concept validation and design. Validation through analyses is especially important since ground testing may be limited due to gravity effects and structural size. The present investigation has the objective to present an examination of the analytical modeling of pretensioned members undergoing nonlinear vibrations. Two approximate nonlinear analysis are developed to model general structural arrangements which include beam-columns and pretensioned cables attached to a common nucleus, such as may occur at a joint of a pretensioned structure. Attention is given to structures undergoing nonlinear steady-state oscillations due to sinusoidal excitation forces. Three analyses, linear, quasi-linear, and nonlinear are conducted and applied to study the response of a relatively simple cable stiffened structure.

Housner, J. M.↗
NASA NTRS1989

Calculation of the electron wave function in a graded-channel double-heterojunction modulation-doped field-effect transistor

Three double-heterojunction modulation-doped field-effect transistor structures with different channel composition are investigated theoretically. All of these transistors have an In(x)Ga(1-x)As channel sandwiched between two doped Al(0.3)Ga(0.7)As barriers with undoped spacer layers. In one of the structures, x varies from 0 from either heterojunction to 0.15 at the center of the channel quadratically; in the other two, constant values of x of 0 and 0.15 are used. The Poisson and Schroedinger equations are solved self-consistently for the electron wave function in all three cases. The results showed that the two-dimensional electron gas (2DEG) concentration in the channel of the quadratically graded structure is higher than the x = 0 one and slightly lower than the x = 0.15 one, and the mean distance of the 2DEG is closer to the center of the channel for this transistor than the other two. These two effects have important implications on the electron mobility in the channel.

Mui, D. S. L.↗
NASA NTRS1998

The Feasibility of Bulk Crystallization as an Industrial Purification and Production Technique for Proteins

Bulk crystallization in stirred vessels is used industrially for the recovery and purification of many inorganic and organic materials. Although much has been written on the crystallization of proteins for X-ray diffraction analysis, very little has been reported on the application of bulk crystallization in stirred vessels. In this study, a 1-liter, seeded, stirred, batch crystallizer was used with ovalbumin as a model protein to test the feasibility of this crystallization method as a recovery and purification process for proteins. Results were obtained for ovalbumin solubility, nucleation thresholds, crystal breakage and crystal growth kinetics in bulk solution under a range of operating conditions of pH and ammonium sulphate concentration (Judge et al., 1996). Experiments were also performed to determine the degree of purification that can be achieved by the crystallization of ovalbumin from a mixture of proteins. The effect of the presence of these proteins upon the ovalbumin crystal growth kinetics was also investigated (Judge et al., 1995). All of these aspects are essential for the design of bulk crystallization processes which have not previously been reported for proteins. Results from a second study that investigated the effect of structurally different proteins on the solubility, crystal growth rates and crystal purity of chicken egg white lysozyme are also presented (Judge et al., 1997). In this case face growth rates were measured using lysozyme purified by liquid chromatography and the effect of the addition of specific protein impurities were observed on the (110) and (101) crystal faces. In these two studies the results are presented to show the feasibility and purifying ability of crystallization as a production process for proteins.

Judge, Russell A.↗
DOE OSTI2024

Effects of N -glycans on the structure of human IgA2

The transition of IgA antibodies into clinical development is crucial because they have the potential to create a new class of therapeutics with superior pathogen neutralization, cancer cell killing, and immunomodulation capacity compared to IgG. However, the biological role of IgA glycans in these processes needs to be better understood. This study provides a detailed biochemical, biophysical, and structural characterization of recombinant monomeric human IgA2, which varies in the amount/locations of attached glycans. Monomeric IgA2 antibodies were produced by removing the N-linked glycans in the CH1 and CH2 domains. The impact of glycans on oligomer formation, thermal stability, and receptor binding was evaluated. In addition, we performed a structural analysis of recombinant IgA2 in solution using Small Angle X-Ray Scattering (SAXS) to examine the effect of glycans on protein structure and flexibility. Our results indicate that the absence of glycans in the Fc tail region leads to higher-order aggregates. SAXS, combined with atomistic modeling, showed that the lack of glycans in the CH2 domain results in increased flexibility between the Fab and Fc domains and a different distribution of open and closed conformations in solution. When binding with the Fcα-receptor, the dissociation constant remains unaltered in the absence of glycans in the CH1 or CH2 domain, compared to the fully glycosylated protein. These results provide insights into N-glycans’ function on IgA2, which could have important implications for developing more effective IgA-based therapeutics in the future.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Monodomain Liquid‐Crystal Elastomer Lattices for Broad Strain‐Rate Mechanical Damping

Designing structures that effectively dissipate energy across a broad range of mechanical loading rates, including those from compression, shock, and vibration, poses a significant engineering challenge. In this study, liquid‐crystal elastomers (LCEs), which possess anisotropic properties due to the alignment of their polymer backbone, are explored. As a result, LCEs exhibit a soft elastic response under mechanical loading, making them ideal for energy dissipation. Advances in additive manufacturing (AM) enable simple fabrication of foamlike dissipative structures with complex lattice geometries. Herein, direct ink write 3D printing, an extrusion AM method, is used to fabricate aligned, monodomain LCE lattice structures for broad strain‐rate mechanical damping. In this work, it is shown that these structures can dissipate strain energy in quasi‐static environments, comparable to traditional elastomeric lattices, and provide improved damping under high strain‐rate drop testing due to LCE soft elasticity. Additionally, under dynamic mechanical vibration, monodomain LCE lattices enhance damping at structural natural frequencies and provide high‐frequency attenuation. Finally, in these findings, a promising method is presented for fabricating mechanical damping devices that effectively dissipate energy across a broad range of loading rates.

3D printings↗
DOE OSTI2023

Effect of the filler morphology on the crystallization behavior and dielectric properties of the polyvinylidene fluoride‐based composite

Abstract Ceramic/polymer composites can be chemically stable, mechanically strong, and flexible, which make them candidates for electric devices, such as pressure or temperature sensors, energy storage or harvesting devices, actuators, and so forth. Depending on the application, various electrical properties are of importance. Polymers usually have low dielectric permittivity, but increased dielectric permittivity can be achieved by the addition of the ceramic fillers with high dielectric constant. With the aim to enhance dielectric properties of the composite without loss of flexibility, 5 wt% of BaTiO 3 ‐Fe 2 O 3 powder was added into a polyvinylidene fluoride matrix. The powder was prepared by different synthesis conditions to produce core/shell structures. The effect of the phase composition and morphology of the BaTiO 3 ‐Fe 2 O 3 core/shell filler on the structure and lattice dynamics of the polymer composites was investigated. Based on the results of the thermal analysis, various parameters of ceramic/polymer composites were determined. Differences in the phase composition and morphology of the filler have an influence on the formation of various polyvinylidene fluoride allomorphs and the degree of crystallinity. Furthermore, the dielectric performances of pure polyvinylidene fluoride and the polymer/ceramic composites were measured.

Polymer Science↗
NASA NTRS1992

Probabilistic structural analysis of space truss structures for nonuniform thermal environmental effects

A three-bay, space, cantilever truss is probabilistically evaluated to quantify the range of uncertainties of vibration frequencies and truss free end vertical displacements due to nonuniform thermal loads, applied loads and moments (mechanical loads), and combination of both. The truss members are assumed to be made from (1) aluminum tubes or (2) high modulus graphite-fiber/intermediate modulus epoxy-matrix composite tubes. Cumulative distribution function results show that certain combination of thermal loads with mechanical loads reduce the probabilistic vibration frequencies and increase the magnitude of the truss free end vertical displacements for the aluminum truss. However, for the composite truss, the thermal effects on the probabilistic vibration frequencies are not as substantial as that for an aluminum truss. This can be attributed to the large differences in the values of coefficient of thermal expansion. Finally, the sensitivities associated with the uncertainties in the structural, material and load variables (primative variables) are investigated. Results indicate that vibration frequencies and truss free end vertical displacements are sensitive to the uncertainties in spacial (geometry) variables as well as member modulus.

Pai, Shantaram S.↗
DOE OSTI2021

Cation-size mismatch as a predictive descriptor for structural distortion, configurational disorder, and valence-band splitting in II-IV-N2 semiconductors

The II-IV-N2 class of heterovalent ternary nitrides has gained significant interest as alternatives to the III-nitrides for electronic and optoelectronic applications. In this study, we apply first-principles calculations based on density functional theory to systematically investigate the effects of structural distortions due to cation size mismatch on the configurational disorder of the cation sublattice and the valence band structure in this class of materials. We find that larger size mismatch between the group-II and the group-IV cations results in stronger lattice distortions from the ideal hexagonal ratio, which in turn inhibits the propensity of these materials toward octet-rule violating cation disorder. We also demonstrate that the formation energy of a single cation antisite pair, which is fast and simple to calculate, is a strong indicator of a material's propensity toward disorder. Furthermore, the breaking of in-plane symmetry leads to a splitting of the top three valence bands at Γ, which is also directly related to the magnitude of structural distortions. Our work demonstrates that the structural and functional properties of the II-IV-N2 materials can be finely tuned through controllable structural distortions that stem from the choice of cations.

Kute, Malhar (ORCID:0000000214364564)↗
NASA NTRS1988

Effects of joints in truss structures

The response of truss-type structures for future space applications, such as Large Deployable Reflector (LDR), will be directly affected by joint performance. Some of the objectives of research at BAC were to characterize structural joints, establish analytical approaches that incorporate joint characteristics, and experimentally establish the validity of the analytical approaches. The test approach to characterize joints for both erectable and deployable-type structures was based upon a Force State Mapping Technique. The approach pictorially shows how the nonlinear joint results can be used for equivalent linear analysis. Testing of the Space Station joints developed at LaRC (a hinged joint at 2 Hz and a clevis joint at 2 Hz) successfully revealed the nonlinear characteristics of the joints. The Space Station joints were effectively linear when loaded to plus or minus 500 pounds with a corresponding displacement of about plus or minus 0.0015 inch. It was indicated that good linear joints exist which are compatible with errected structures, but that difficulty may be encountered if nonlinear-type joints are incorporated in the structure.

Ikegami, R.↗
DOE OSTI2018

Anisotropy of Giant Nonlinear Magnetoelectric Effects in Hexaferrites with the Magnetoplumbite Structure

We report on the results of investigation of anisotropy of the nonlinear magnetoelectric current effect in M-type hexaferrites with a collinear magnetic ordering at room temperature. It is found that as a result of the passage of a direct electric current in a plane perpendicular to the hexagonal axis of the strontium hexaferrite sample, the saturation magnetization and the anisotropy constant of the material decrease. The change in the magnetic parameters measured using radio spectroscopic methods is found to be proportional to the supplied electric power density; the determined proportionality factors turn out to be several times larger than in the case when the current passes along the axis. We propose a phenomenological theory that explains the observed effects qualitatively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Design of Fiber Composites for Structural Durability

Hygrothermomechanical effects analyzed by computers. Computational methodology developed and available at NASA Lewis Research Center to design and analyze fiber-composite structures subjected to complex hygrothermomechanical environments. Includes composite mechanics and advanced finited-element structural-analysis methods. Methodology applied to such problems as progressive fracture of composite material, design of composite material for cycle fatigue combined with hot and wet conditions, and general composite-laminate configurations.

Chamis, Christos C.↗
NASA NTRS1989

Ionization effects in the radiative driving of stellar winds in massive X ray binary systems

Massive X ray binaries consist of an early type primary lossing mass via a strong stellar wind driven by the stars radiation field, and an accreting neutron star companion. The X rays from the neutron star affect the wind dynamics by changing the temperature and ionization structure. The effect of the accretion powered X rays on the radiative line force that drives the stellar wind is calculated. The consequences of these calculations for the wind dynamics in massive X ray binaries is discussed.

Stevens, Ian R.↗
DOE OSTI2018

Optimization of Beidellite/Polyaniline Production Conditions by Central Composite Design for Removal of Acid Yellow 194

In the adsorption process, the adsorbent structure and its interaction with wastewater are the main determinant of the process efficiency. For this reason, the correct selection of the production conditions for the produced adsorbents is critical. In this study, the reaction time and the concentration of acid, oxidant, substrate, and monomer were selected as independent variables which effect the structure of the polyaniline based composite material. These production variables of polyaniline/beidellite (PANI/BEI) composites were designed by response surface methodology (RSM). According to RSM, 46 different PANI/BEI composites were synthesized and were used as an adsorbent in the removal of acid yellow 194. Thus, the optimum PANI/BEI production conditions were determined. After the identification of the optimum PANI/BEI production conditions, the effect of adsorption conditions such as pH, mixing time, and dye concentration were studied by batch experiments. The maximum adsorption capacity was obtained as 123 (mg g{sup −1}) at the T = 25 °C, t = 24 h, pH 3, m{sub s} = 0.15 g adsorbent, V{sub s} = 50 ml dye solution, and ω = 200 rpm. The results presented in this study revealed that the central composite design is a suitable method to optimize the production conditions of PANI/BEI and the prepared PANI/BEI composites has an important potential as an adsorbent for the removal of metal-complex dyes such as AY194. In addition, the polymerization of aniline and the removal of dye were confirmed by different analytical techniques such as BET, XRD, SEM, and EDAX.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1981

The dynamics and control of large flexible space structures-IV

The effects of solar radiation pressure as the main environmental disturbance torque were incorporated into the model of the rigid orbiting shallow shell and computer simulation results indicate that within the linear range the rigid modal amplitudes are excited in proportion to the area to mass ratio. The effect of higher order terms in the gravity-gradient torque expressions previously neglected was evaluated and found to be negligible for the size structures under consideration. A graph theory approach was employed for calculating the eigenvalues of a large flexible system by reducing the system (stiffness) matrix to lower ordered submatrices. The related reachability matrix and term rank concepts are used to verify controllability and can be more effective than the alternate numerical rank tests. Control laws were developed for the shape and orientation control of the orbiting flexible shallow shell and numerical results presented.

Bainum, P. M.↗
NASA NTRS1957

Effect of transient heating on vibration frequencies of some simple wing structures

Thermal stresses, which may result from transient heating, can cause changes in the effective stiffness of wing structures. Some effects of this change in stiffness were investigated experimentally by radiantly heating three types of simple wing structures: a uniform plate, a solid double-wedge section, and a circular-arc multiweb-wing section. Changes in stiffness were determined by measuring the changes in natural frequency of vibration during transient heating. Some comparisons are made between theoretical calculations and the measured data.

LOADS AND STRESSES, STRUCTURAL↗
NASA NTRS1982

Coupled rotor/airframe vibration analysis

A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.

Sopher, R.↗
NASA NTRS1994

Evaluation of the fuselage lap joint fatigue and terminating action repair

Terminating action is a remedial repair which entails the replacement of shear head countersunk rivets with universal head rivets which have a larger shank diameter. The procedure was developed to eliminate the risk of widespread fatigue damage (WFD) in the upper rivet row of a fuselage lap joint. A test and evaluation program has been conducted by Foster-Miller, Inc. (FMI) to evaluate the terminating action repair of the upper rivet row of a commercial aircraft fuselage lap splice. Two full scale fatigue tests were conducted on fuselage panels using the growth of fatigue cracks in the lap joint. The second test was performed to evaluate the effectiveness of the terminating action repair. In both tests, cyclic pressurization loading was applied to the panels while crack propagation was recorded at all rivet locations at regular intervals to generate detailed data on conditions of fatigue crack initiation, ligament link-up, and fuselage fracture. This program demonstrated that the terminating action repair substantially increases the fatigue life of a fuselage panel structure and effectively eliminates the occurrence of cracking in the upper rivet row of the lap joint. While high cycle crack growth was recorded in the middle rivet row during the second test, failure was not imminent when the test was terminated after cycling to well beyond the service life. The program also demonstrated that the initiation, propagation, and linkup of WFD in full-scale fuselage structures can be simulated and quantitatively studied in the laboratory. This paper presents an overview of the testing program and provides a detailed discussion of the data analysis and results. Crack distribution and propagation rates and directions as well as frequency of cracking are presented for both tests. The progression of damage to linkup of adjacent cracks and to eventual overall panel failure is discussed. In addition, an assessment of the effectiveness of the terminating action repair and the occurrence of cracking in the middle rivet row is provided, and conclusions of practical interest are drawn.

Samavedam, Gopal↗
DOE OSTI2018

SiO 2 -Enhanced Structural Stability and Strong Adhesion with a New Binder of Konjac Glucomannan Enables Stable Cycling of Silicon Anodes for Lithium-Ion Batteries

Silicon-based anodes with high theoretical capacity have intriguing potential applications for next-generation high-energy lithium-ion batteries, but suffer from huge volumetric change that causes pulverization of electrodes. Rational design and construction of effective electrode structures combined with versatile binders remain a significant challenge. In this paper, a unique natural binder of konjac glucomannan (KGM) is developed and an amorphous protective layer of SiO 2 is fabricated on the surface of Si nanoparticles (Si@SiO 2 ) to enhance the adhesion. Benefiting from a plethora of hydroxyl groups, the KGM binder with inherently high adhesion and superior mechanical properties provides abundant contact sites to active materials. Molecular mechanics simulations and experimental results demonstrate that the enhanced adhesion between KGM and Si@SiO 2 can bond the particles tightly to form a robust electrode. In addition to bridging KGM molecules, the SiO 2 -functionalized surface may serve as a buffer layer to alleviate the stresses of Si nanoparticles resulting from the volume change. The as-fabricated KGM/Si@SiO 2 electrode exhibits outstanding structural stability upon long-term cycles. Finally, a highly reversible capacity of 1278 mAh g -1 can be achieved over 1000 cycles at a current density of 2 A g -1 , and the capacity decay is as small as 0.056% per cycle.

25 ENERGY STORAGE↗