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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Autogenic succession and deterministic recovery following disturbance in soil bacterial communities

The response of bacterial communities to environmental change may affect local to global nutrient cycles; however the dynamics of these communities following disturbance are poorly understood, and are generally attributed to abiotic factors. Here, we subjected soil microcosms to a heat disturbance and followed the community composition of active bacteria over 50 days of recovery. Phylogenetic turnover patterns indicated that biotic interactions shaped the community during recovery, and that the disturbance imposed a strong selective pressure that persisted for up to 10 days, after which the importance of stochastic processes increased. Three successional stages were detected: a primary response (1-4 days after disturbance) in which surviving taxa increased in abundance; a secondary response phase (10-29 days), during which community dynamics slowed down, and a stability phase (after 29 days), during which the community tended towards its original composition. Furthermore, soil bacterial communities, despite their extreme diversity and functional redundancy, respond to disturbances like many macroecological systems and exhibit path-dependent, autogenic dynamics during secondary succession.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Shear-enhanced adhesiveless transfer printing for use in deterministic materials assembly

Here, this letter describes the physics and application of an approach to transfer printing that utilizes targeted shear loading to modulate stamp adhesion in a controlled and repeatable fashion. Experimental measurements of pull-off forces as functions of shear and stamp dimension reveal key scaling properties and provide a means for comparison to theory and modeling. Examples of printed structures in suspended and multilayer configurations demonstrate some capabilities in micro/nanoscale materials assembly.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The deterministic chaos and random noise in turbulent jet

A turbulent flow is usually treated as a superposition of coherent structure and incoherent turbulence. In this paper, the largest Lyapunov exponent and the random noise in the near field of round jet and plane jet are estimated with our previously proposed method of chaotic time series analysis [T. L. Yao, et al., Chaos 22, 033102 (2012)]. The results show that the largest Lyapunov exponents of the round jet and plane jet are in direct proportion to the reciprocal of the integral time scale of turbulence, which is in accordance with the results of the dimensional analysis, and the proportionality coefficients are equal. In addition, the random noise of the round jet and plane jet has the same linear relation with the Kolmogorov velocity scale of turbulence. As a result, the random noise may well be from the incoherent disturbance in turbulence, and the coherent structure in turbulence may well follow the rule of chaotic motion.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Deterministic and cascadable conditional phase gate for photonic qubits

Previous analyses of conditional φ{sub NL}-phase gates for photonic qubits that treat crossphase modulation (XPM) in a causal, multimode, quantum field setting suggest that a large (∼π rad) nonlinear phase shift is always accompanied by fidelity-degrading noise [J. H. Shapiro, Phys. Rev. A 73, 062305 (2006); J. Gea-Banacloche, Phys. Rev. A 81, 043823 (2010)]. Using an atomic V-system to model an XPM medium, we present a conditional phase gate that, for sufficiently small nonzero φ{sub NL}, has high fidelity. The gate is made cascadable by using a special measurement, principal mode projection, to exploit the quantum Zeno effect and preclude the accumulation of fidelity-degrading departures from the principal-mode Hilbert space when both control and target photons illuminate the gate. The nonlinearity of the V-system we study is too weak for this particular implementation to be practical. Nevertheless, the idea of cascading through principal mode projection is of potential use to overcome fidelity degrading noise for a wide variety of nonlinear optical primitive gates.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Deterministic switching of a magnetoelastic single-domain nano-ellipse using bending

In this paper, a fully coupled analytical model between elastodynamics with micromagnetics is used to study the switching energies using voltage induced mechanical bending of a magnetoelastic bit. The bit consists of a single domain magnetoelastic nano-ellipse deposited on a thin film piezoelectric thin film (500 nm) attached to a thick substrate (0.5 mm) with patterned electrodes underneath the nano-dot. A voltage applied to the electrodes produces out of plane deformation with bending moments induced in the magnetoelastic bit modifying the magnetic anisotropy. To minimize the energy, two design stages are used. In the first stage, the geometry and bias field (H{sub b}) of the bit are optimized to minimize the strain energy required to rotate between two stable states. In the second stage, the bit's geometry is fixed, and the electrode position and control mechanism is optimized. The electrical energy input is about 200 (aJ) which is approximately two orders of magnitude lower than spin transfer torque approaches.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Design criteria for XeF{sub 2} enabled deterministic transformation of bulk silicon (100) into flexible silicon layer

Isotropic etching of bulk silicon (100) using Xenon Difluoride (XeF{sub 2}) gas presents a unique opportunity to undercut and release ultra-thin flexible silicon layers with pre-fabricated state-of-the-art Complementary Metal Oxide Semiconductor (CMOS) electronics. In this work, we present design criteria and mechanism with a comprehensive mathematical model for this method. We consider various trench geometries and parametrize important metrics such as etch time, number of cycles and area efficiency in terms of the trench diameter and spacing so that optimization can be done for specific applications. From our theoretical analysis, we conclude that a honeycomb-inspired hexagonal distribution of trenches can produce the most efficient release of ultra-thin flexible silicon layers in terms of the number of etch cycles, while a rectangular distribution of circular trenches provides the most area efficient design. The theoretical results are verified by fabricating and releasing (varying sizes) flexible silicon layers. We observe uniform translation of design criteria into practice for etch distances and number of etch cycles, using reaction efficiency as a fitting parameter.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Deterministic modeling of hybrid nonlinear effects in epsilon-near-zero thin films

In nonlinear optics, significant effort is concentrated on improving the strength and efficiency of interactions; however, experimentally investigating nonlinear materials is a complex, time-consuming, and costly investment. Moreover, it is often challenging to isolate, study, and optimize material parameters in an experiment due to complexities in the growth process. Recently, epsilon-near-zero materials have received a great deal of attention as promising nonlinear optical materials, but like many up-and-coming materials, the ability to explore and optimize their properties has been challenging. Here, we establish a framework to rapidly evaluate the performance of nonlinear epsilon-near-zero materials for both inter- and intraband effects in silico, requiring only an energy-momentum (E-k) diagram, linear optical properties, and experimental conditions. Measured nonlinear reflection and transmission in gallium-doped zinc oxide films are compared to the numerical framework for both intra- and interband excitation to verify accuracy across wavelength and irradiance while two figures of merit (FoMs) are introduced to quickly evaluate the performance of films without a full numerical framework. This capability is used to predict the performance of highly doped gallium nitride, cadmium oxide, zinc oxide, and indium tin oxide films, and efficient intra- and interband operation conditions are identified. Through this numerical framework and the FoMs, the exploration of unstudied epsilon-near-zero materials is enabled without the need for a nonlinear experiment, thereby accelerating the search for more efficient nonlinear materials and excitation conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Effect of roughness, deterministic and random errors in film thickness on the reflecting properties of aperiodic mirrors for the EUV range

By the example of three aperiodic multilayer Mo/Si mirrors (AMM) for the wavelength ranges 17–21 nm, 24–29 nm, and 28–33 nm we have studied numerically the effect of the linearly determinisctic and random fluctuations of the film thickness and the interlayer roughness on the spectral dependences of the reflection coefficient. The simulation results are used to solve the inverse problem of reconstructing the interlayer roughness and the thickness of individual films from the measured dependences of the extreme UV radiation reflection coefficients. It is shown that the 'asymmetry' of the boundaries affects the magnitude and slope of the reflection coefficient plateau. Random fluctuations of the film thickness with the variance of 1%–2% weakly influence the reflection characteristics of AMMs and allow reliable reconstruction of the thickness of individual films. The fluctuations with the variance 8%–10% allow the estimation of individual thicknesses, but the reflection curve in this case strongly differs from the desirable one. Larger fluctuations do not allow the reconstruction of the AMM structure. The basic criteria for high-quality AMM synthesis are formulated. (extreme laser radiation: physics and fundamental applications)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Deterministic fabrication of graphene hexagonal boron nitride moiré superlattices

The electronic properties of moiré heterostructures depend sensitively on the relative orientation between layers of the stack. For example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample with one of the graphene layers rotationally aligned to a hexagonal Boron Nitride (hBN) cladding layer provided experimental observation of orbital ferromagnetism. To create samples with aligned graphene/hBN, researchers often align edges of exfoliated flakes that appear straight in optical micrographs. However, graphene or hBN can cleave along either zig-zag or armchair lattice directions, introducing a 30° ambiguity in the relative orientation of two flakes. By characterizing the crystal lattice orientation of exfoliated flakes prior to stacking using Raman and second-harmonic generation for graphene and hBN, respectively, we unambiguously align monolayer graphene to hBN at a near-0°, not 30°, relative twist angle. We confirm this alignment by torsional force microscopy of the graphene/hBN moiré on an open-face stack, and then by cryogenic transport measurements, after full encapsulation with a second, nonaligned hBN layer. This work demonstrates a key step toward systematically exploring the effects of the relative twist angle between dissimilar materials within moiré heterostructures.

boron nitride↗
DOE OSTI2010

TOWARD A DETERMINISTIC MODEL OF PLANETARY FORMATION. VI. DYNAMICAL INTERACTION AND COAGULATION OF MULTIPLE ROCKY EMBRYOS AND SUPER-EARTH SYSTEMS AROUND SOLAR-TYPE STARS

Radial velocity and transit surveys indicate that solar-type stars bear super-Earths, with masses up to {approx}20 M {sub +} and periods up to a few months, that are more common than those with Jupiter-mass gas giants. In many cases, these super-Earths are members of multiple-planet systems in which their mutual dynamical interaction has influenced their formation and evolution. In this paper, we modify an existing numerical population synthesis scheme to take into account protoplanetary embryos' interaction with their evolving natal gaseous disks, as well as their close scatterings and resonant interaction with each other. We show that it is possible for a group of compact embryos to emerge interior to the ice line, grow, migrate, and congregate into closely packed convoys which stall in the proximity of their host stars. After the disk-gas depletion, they undergo orbit crossing, close scattering, and giant impacts to form multiple rocky Earths or super-Earths in non-resonant orbits around {approx}0.1 AU with moderate eccentricities of {approx}0.01-0.1. We suggest that most refractory super-Earths with periods in the range of a few days to weeks may have formed through this process. These super-Earths differ from Neptune-like ice giants by their compact sizes and lack of a substantial gaseous envelope.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

TOWARD A DETERMINISTIC MODEL OF PLANETARY FORMATION. VII. ECCENTRICITY DISTRIBUTION OF GAS GIANTS

The ubiquity of planets and diversity of planetary systems reveal that planet formation encompasses many complex and competing processes. In this series of papers, we develop and upgrade a population synthesis model as a tool to identify the dominant physical effects and to calibrate the range of physical conditions. Recent planet searches have led to the discovery of many multiple-planet systems. Any theoretical models of their origins must take into account dynamical interactions between emerging protoplanets. Here, we introduce a prescription to approximate the close encounters between multiple planets. We apply this method to simulate the growth, migration, and dynamical interaction of planetary systems. Our models show that in relatively massive disks, several gas giants and rocky/icy planets emerge, migrate, and undergo dynamical instability. Secular perturbation between planets leads to orbital crossings, eccentricity excitation, and planetary ejection. In disks with modest masses, two or less gas giants form with multiple super-Earths. Orbital stability in these systems is generally maintained and they retain the kinematic structure after gas in their natal disks is depleted. These results reproduce the observed planetary mass-eccentricity and semimajor axis-eccentricity correlations. They also suggest that emerging gas giants can scatter residual cores to the outer disk regions. Subsequent in situ gas accretion onto these cores can lead to the formation of distant (∼> 30 AU) gas giants with nearly circular orbits.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

ENHANCEMENTS IN THE TECHA RIVER DOSIMETRY SYSTEM: TRDS-2016D CODE FOR RECONSTRUCTION OF DETERMINISTIC ESTIMATES OF DOSE FROM ENVIRONMENTAL EXPOSURES

Waterborne releases to the Techa River from the Mayak plutonium facility in Russia during 1949–1956 resulted in significant doses to persons living downstream. The dosimetry system TRDS-2016D has been developed which provides individual doses of external and internal exposure for the members of the Techa River Cohort (TRC) and other persons, who were exposed to releases of radioactive material to the Southern Urals. The results of computation of individual doses absorbed in red bone marrow and extra-skeletal tissues for the TRC members (29,647 persons) are presented, which are based on residence histories on the contaminated Techa River and the East Urals Radioactive Trace (EURT) which was formed in 1957 as a result of the Kyshtym Accident. Available 90Sr-body-burden measurements and available information on individual household locations have been used for refinement of individual dose estimates. TRDS-2016D-based dose estimates will be used for verification of risk of low-dose-rate effects of ionizing radiation in the TRC.

dose reconstruction, environmental contamination, ↗
DOE OSTI2010

Deterministic source of a train of indistinguishable single-photon pulses with a single-atom-cavity system

We present a mechanism to produce indistinguishable single-photon pulses on demand from an optical cavity. The sequences of two laser pulses generate, at the two Raman transitions of a four-level atom, the same cavity-mode photons without repumping of the atom between photon generations. Photons are emitted from the cavity with near-unit efficiency in well-defined temporal modes of identical shapes controlled by the laser fields. The second-order correlation function reveals the single-photon nature of the proposed source. A realistic setup for the experimental implementation is presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Deterministic creation and stabilization of entanglement in circuit QED by homodyne-mediated feedback control

In a solid-state circuit QED system, we demonstrate that a homodyne-current-based feedback can create and stabilize highly entangled two-qubit states in the presence of a moderate noisy environment. Particularly, we present an extended analysis for the current-based Markovian feedback, which leads to an improved feedback scheme. We show that this is essential to achieve a desirable control effect by the use of dispersive measurement.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Deterministic generation of a three-dimensional entangled state via quantum Zeno dynamics

A scheme is proposed for the generation of a three-dimensional entangled state for two atoms trapped in a cavity via quantum Zeno dynamics. Because the scheme is based on the resonant interaction, the time required to produce entanglement is very short compared with the dispersive protocols. We show that the resulting effective dynamics allows for the creation of robust qutrit-qutrit entanglement. The influence of various decoherence processes such as spontaneous emission and photon loss on the fidelity of the entangled state is investigated. Numerical results show that the scheme is robust against the cavity decay since the evolution of the system is restricted to a subspace with null-excitation cavity fields. Furthermore, the present scheme has been generalized to realize N-dimensional entanglement for two atoms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Deterministic generation of a pair of entangled guided photons from a single atom in a nanofiber cavity

We investigate the controlled production of entangled guided photons. The technique is based on a two-stage vacuum-stimulated Raman process with a single atom in a nanofiber cavity. We examine the dependences of the two-photon emission probability and the entanglement concurrence on various parameters of the system, such as the radial and axial positions of the atom, the intensities and durations of the pump pulses, the one- and two-photon detunings, the cavity finesse, and the separation time between the pump pulses. We find that, due to the confinement of the guided cavity field in the transverse plane of the fiber and in the space between the cavity mirrors, the probability of generation of a pair of entangled guided photon can be high even when the finesse of the nanofiber cavity is moderate.

74 ATOMIC AND MOLECULAR PHYSICS↗