Efficient Geometry Minimization and Transition Structure Optimization Using Interpolated Potential Energy Surfaces and Iteratively Updated Hessians.

PubMed

Zheng, Jingjing; Frisch, Michael J

2017-12-12

An efficient geometry optimization algorithm based on interpolated potential energy surfaces with iteratively updated Hessians is presented in this work. At each step of geometry optimization (including both minimization and transition structure search), an interpolated potential energy surface is properly constructed by using the previously calculated information (energies, gradients, and Hessians/updated Hessians), and Hessians of the two latest geometries are updated in an iterative manner. The optimized minimum or transition structure on the interpolated surface is used for the starting geometry of the next geometry optimization step. The cost of searching the minimum or transition structure on the interpolated surface and iteratively updating Hessians is usually negligible compared with most electronic structure single gradient calculations. These interpolated potential energy surfaces are often better representations of the true potential energy surface in a broader range than a local quadratic approximation that is usually used in most geometry optimization algorithms. Tests on a series of large and floppy molecules and transition structures both in gas phase and in solutions show that the new algorithm can significantly improve the optimization efficiency by using the iteratively updated Hessians and optimizations on interpolated surfaces.

Probing the global potential energy minimum of (CH2O)2: THz absorption spectrum of (CH2O)2 in solid neon and para-hydrogen.

PubMed

Andersen, J; Voute, A; Mihrin, D; Heimdal, J; Berg, R W; Torsson, M; Wugt Larsen, R

2017-06-28

The true global potential energy minimum configuration of the formaldehyde dimer (CH 2 O) 2 , including the presence of a single or a double weak intermolecular CH⋯O hydrogen bond motif, has been a long-standing subject among both experimentalists and theoreticians as two different energy minima conformations of C s and C 2h symmetry have almost identical energies. The present work demonstrates how the class of large-amplitude hydrogen bond vibrational motion probed in the THz region provides excellent direct spectroscopic observables for these weak intermolecular CH⋯O hydrogen bond motifs. The combination of concentration dependency measurements, observed isotopic spectral shifts associated with H/D substitutions and dedicated annealing procedures, enables the unambiguous assignment of three large-amplitude infrared active hydrogen bond vibrational modes for the non-planar C s configuration of (CH 2 O) 2 embedded in cryogenic neon and enriched para-hydrogen matrices. A (semi)-empirical value for the change of vibrational zero-point energy of 5.5 ± 0.3 kJ mol -1 is proposed for the dimerization process. These THz spectroscopic observations are complemented by CCSD(T)-F12/aug-cc-pV5Z (electronic energies) and MP2/aug-cc-pVQZ (force fields) electronic structure calculations yielding a (semi)-empirical value of 13.7 ± 0.3 kJ mol -1 for the dissociation energy D 0 of this global potential energy minimum.

Probing the global potential energy minimum of (CH2O)2: THz absorption spectrum of (CH2O)2 in solid neon and para-hydrogen

NASA Astrophysics Data System (ADS)

Andersen, J.; Voute, A.; Mihrin, D.; Heimdal, J.; Berg, R. W.; Torsson, M.; Wugt Larsen, R.

2017-06-01

The true global potential energy minimum configuration of the formaldehyde dimer (CH2O)2, including the presence of a single or a double weak intermolecular CH⋯O hydrogen bond motif, has been a long-standing subject among both experimentalists and theoreticians as two different energy minima conformations of Cs and C2h symmetry have almost identical energies. The present work demonstrates how the class of large-amplitude hydrogen bond vibrational motion probed in the THz region provides excellent direct spectroscopic observables for these weak intermolecular CH⋯O hydrogen bond motifs. The combination of concentration dependency measurements, observed isotopic spectral shifts associated with H/D substitutions and dedicated annealing procedures, enables the unambiguous assignment of three large-amplitude infrared active hydrogen bond vibrational modes for the non-planar Cs configuration of (CH2O)2 embedded in cryogenic neon and enriched para-hydrogen matrices. A (semi)-empirical value for the change of vibrational zero-point energy of 5.5 ± 0.3 kJ mol-1 is proposed for the dimerization process. These THz spectroscopic observations are complemented by CCSD(T)-F12/aug-cc-pV5Z (electronic energies) and MP2/aug-cc-pVQZ (force fields) electronic structure calculations yielding a (semi)-empirical value of 13.7 ± 0.3 kJ mol-1 for the dissociation energy D0 of this global potential energy minimum.

A New Potential Energy Surface for N+O2: Is There an NOO Minimum?

NASA Technical Reports Server (NTRS)

Walch, Stephen P.

1995-01-01

We report a new calculation of the N+02 potential energy surface using complete active space self-consistent field internally contracted configuration interaction with the Dunning correlation consistent basis sets. The peroxy isomer of N02 is found to be a very shallow minimum separated from NO+O by a barrier of only 0.3 kcal/mol (excluding zero-point effects). The entrance channel barrier height is estimated to be 8.6 kcal/mol for ICCI+Q calculations correlating all but the Ols and N1s electrons with a cc-p VQZ basis set.

A strategy to find minimal energy nanocluster structures.

PubMed

Rogan, José; Varas, Alejandro; Valdivia, Juan Alejandro; Kiwi, Miguel

2013-11-05

An unbiased strategy to search for the global and local minimal energy structures of free standing nanoclusters is presented. Our objectives are twofold: to find a diverse set of low lying local minima, as well as the global minimum. To do so, we use massively the fast inertial relaxation engine algorithm as an efficient local minimizer. This procedure turns out to be quite efficient to reach the global minimum, and also most of the local minima. We test the method with the Lennard-Jones (LJ) potential, for which an abundant literature does exist, and obtain novel results, which include a new local minimum for LJ13 , 10 new local minima for LJ14 , and thousands of new local minima for 15≤N≤65. Insights on how to choose the initial configurations, analyzing the effectiveness of the method in reaching low-energy structures, including the global minimum, are developed as a function of the number of atoms of the cluster. Also, a novel characterization of the potential energy surface, analyzing properties of the local minima basins, is provided. The procedure constitutes a promising tool to generate a diverse set of cluster conformations, both two- and three-dimensional, that can be used as an input for refinement by means of ab initio methods. Copyright © 2013 Wiley Periodicals, Inc.

Minimum energy efficiency standards for appliances: Old and new economic rationales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houde, Sebastien; Spurlock, C. Anna

In this study, we revisit Hausman and Joskow (1982)'s economic rationales for appliance minimum energy efficiency standards. In addition to the four market failures they argued could justify appliance standards--energy prices below marginal social cost, consumers underestimating energy prices, consumer discount rates above social discount rates, or principal agent problems--we discuss two additional market failures that are relevant and potentially economically important in this context: market power and innovation market failures. We highlight puzzles uncovered by recent empirical results, and suggest directions future research should take to better understand the normative implications of appliance standards.

Minimum energy efficiency standards for appliances: Old and new economic rationales

DOE PAGES

Houde, Sebastien; Spurlock, C. Anna

2016-09-01

In this study, we revisit Hausman and Joskow (1982)'s economic rationales for appliance minimum energy efficiency standards. In addition to the four market failures they argued could justify appliance standards--energy prices below marginal social cost, consumers underestimating energy prices, consumer discount rates above social discount rates, or principal agent problems--we discuss two additional market failures that are relevant and potentially economically important in this context: market power and innovation market failures. We highlight puzzles uncovered by recent empirical results, and suggest directions future research should take to better understand the normative implications of appliance standards.

Towards black-box calculations of tunneling splittings obtained from vibrational structure methods based on normal coordinates.

PubMed

Neff, Michael; Rauhut, Guntram

2014-02-05

Multidimensional potential energy surfaces obtained from explicitly correlated coupled-cluster calculations and further corrections for high-order correlation contributions, scalar relativistic effects and core-correlation energy contributions were generated in a fully automated fashion for the double-minimum benchmark systems OH3(+) and NH3. The black-box generation of the potentials is based on normal coordinates, which were used in the underlying multimode expansions of the potentials and the μ-tensor within the Watson operator. Normal coordinates are not the optimal choice for describing double-minimum potentials and the question remains if they can be used for accurate calculations at all. However, their unique definition is an appealing feature, which removes remaining errors in truncated potential expansions arising from different choices of curvilinear coordinate systems. Fully automated calculations are presented, which demonstrate, that the proposed scheme allows for the determination of energy levels and tunneling splittings as a routine application. Copyright © 2013 Elsevier B.V. All rights reserved.

Energy Minimization of Discrete Protein Titration State Models Using Graph Theory.

PubMed

Purvine, Emilie; Monson, Kyle; Jurrus, Elizabeth; Star, Keith; Baker, Nathan A

2016-08-25

There are several applications in computational biophysics that require the optimization of discrete interacting states, for example, amino acid titration states, ligand oxidation states, or discrete rotamer angles. Such optimization can be very time-consuming as it scales exponentially in the number of sites to be optimized. In this paper, we describe a new polynomial time algorithm for optimization of discrete states in macromolecular systems. This algorithm was adapted from image processing and uses techniques from discrete mathematics and graph theory to restate the optimization problem in terms of "maximum flow-minimum cut" graph analysis. The interaction energy graph, a graph in which vertices (amino acids) and edges (interactions) are weighted with their respective energies, is transformed into a flow network in which the value of the minimum cut in the network equals the minimum free energy of the protein and the cut itself encodes the state that achieves the minimum free energy. Because of its deterministic nature and polynomial time performance, this algorithm has the potential to allow for the ionization state of larger proteins to be discovered.

Energy Minimization of Discrete Protein Titration State Models Using Graph Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purvine, Emilie AH; Monson, Kyle E.; Jurrus, Elizabeth R.

There are several applications in computational biophysics which require the optimization of discrete interacting states; e.g., amino acid titration states, ligand oxidation states, or discrete rotamer angles. Such optimization can be very time-consuming as it scales exponentially in the number of sites to be optimized. In this paper, we describe a new polynomial-time algorithm for optimization of discrete states in macromolecular systems. This algorithm was adapted from image processing and uses techniques from discrete mathematics and graph theory to restate the optimization problem in terms of maximum flow-minimum cut graph analysis. The interaction energy graph, a graph in which verticesmore » (amino acids) and edges (interactions) are weighted with their respective energies, is transformed into a flow network in which the value of the minimum cut in the network equals the minimum free energy of the protein, and the cut itself encodes the state that achieves the minimum free energy. Because of its deterministic nature and polynomial-time performance, this algorithm has the potential to allow for the ionization state of larger proteins to be discovered.« less

Energy Minimization of Discrete Protein Titration State Models Using Graph Theory

PubMed Central

Purvine, Emilie; Monson, Kyle; Jurrus, Elizabeth; Star, Keith; Baker, Nathan A.

2016-01-01

There are several applications in computational biophysics which require the optimization of discrete interacting states; e.g., amino acid titration states, ligand oxidation states, or discrete rotamer angles. Such optimization can be very time-consuming as it scales exponentially in the number of sites to be optimized. In this paper, we describe a new polynomial-time algorithm for optimization of discrete states in macromolecular systems. This algorithm was adapted from image processing and uses techniques from discrete mathematics and graph theory to restate the optimization problem in terms of “maximum flow-minimum cut” graph analysis. The interaction energy graph, a graph in which vertices (amino acids) and edges (interactions) are weighted with their respective energies, is transformed into a flow network in which the value of the minimum cut in the network equals the minimum free energy of the protein, and the cut itself encodes the state that achieves the minimum free energy. Because of its deterministic nature and polynomial-time performance, this algorithm has the potential to allow for the ionization state of larger proteins to be discovered. PMID:27089174

Multistate metadynamics for automatic exploration of conical intersections

NASA Astrophysics Data System (ADS)

Lindner, Joachim O.; Röhr, Merle I. S.; Mitrić, Roland

2018-05-01

We introduce multistate metadynamics for automatic exploration of conical intersection seams between adiabatic Born-Oppenheimer potential energy surfaces in molecular systems. By choosing the energy gap between the electronic states as a collective variable the metadynamics drives the system from an arbitrary ground-state configuration toward the intersection seam. Upon reaching the seam, the multistate electronic Hamiltonian is extended by introducing biasing potentials into the off-diagonal elements, and the molecular dynamics is continued on a modified potential energy surface obtained by diagonalization of the latter. The off-diagonal bias serves to locally open the energy gap and push the system to the next intersection point. In this way, the conical intersection energy landscape can be explored, identifying minimum energy crossing points and the barriers separating them. We illustrate the method on the example of furan, a prototype organic molecule exhibiting rich photophysics. The multistate metadynamics reveals plateaus on the conical intersection energy landscape from which the minimum energy crossing points with characteristic geometries can be extracted. The method can be combined with the broad spectrum of electronic structure methods and represents a generally applicable tool for the exploration of photophysics and photochemistry in complex molecules and materials.

Ground state energy of electrons in a static point-ion lattice

NASA Technical Reports Server (NTRS)

Styer, D. F.; Ashcroft, N. W.

1983-01-01

The ground state energy of a neutral collection of protons and electrons was investigated under the assumption that in the ground state configuration, static protons occupy the sites of a rigid Bravais lattice. The Wigner-Seitz method was used in conjunction with three postulated potentials: bare Coulomb, Thomas-Fermi screening, and screening by a uniform bare background charge. Within these approximations, the exact band-minimum energy and wave functions are derived. For each of the three potentials, the approximate minimum ground state energy per proton (relative to isolated electrons and protons) is, respectively, -1.078 Ry, -1.038 Ry, and -1.052 Ry. These three minima all fall at a density of about 0.60 gm/cu cm, which is thus an approximate lower bound on the density of metallic hydrogen at its transition pressure.

Ab Initio and Analytic Intermolecular Potentials for Ar–CH3OH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tasic, Uros; Alexeev, Yuri; Vayner, Grigoriy

2006-09-20

Ab initio calculations at the CCSD(T)/aug-cc-pVTZ level of theory were used to characterize the Ar–CH₃y6tOH intermolecular potential energy surface (PES). Potential energy curves were calculated for four different Ar + CH₃OH orientations and used to derive an analytic function for the intermolecular PES. A sum of Ar–C, Ar–O, Ar–H(C), and Ar–H(O) two-body potentials gives an excellent fit to these potential energy curves up to 100 kcal mol¯¹, and adding an additional r¯¹n term to the Buckingham two-body potential results in only a minor improvement in the fit. Three Ar–CH₃OH van der Waals minima were found from the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ calculations. Themore » structure of the global minimum is in overall good agreement with experiment (X.-C. Tan, L. Sun and R. L. Kuczkowski, J. Mol. Spectrosc., 1995, 171, 248). It is T-shaped with the hydroxyl H-atom syn with respect to Ar. Extrapolated to the complete basis set (CBS) limit, the global minimum has a well depth of 0.72 kcal mol¯¹ with basis set superposition error (BSSE) correction. The aug-cc-pVTZ basis set gives a well depth only 0.10 kcal mol¯¹ smaller than this value. The well depths of the other two minima are within 0.16 kcal mol¯¹ of the global minimum. The analytic Ar–CH₃OH intermolecular potential also identifies these three minima as the only van der Waals minima and the structures predicted by the analytic potential are similar to the ab initio structures. The analytic potential identifies the same global minimum and the predicted well depths for the minima are within 0.05 kcal mol¯1 of the ab initio values. Combining this Ar–CH₃OH intermolecular potential with a potential for a OH-terminated alkylthiolate self-assembled monolayer surface (i.e., HO-SAM) provides a potential to model Ar + HO-SAM collisions.« less

Lowest-energy structures of (C60)nX (X=Li+,Na+,K+,Cl-) and (C60)nYCl (Y=Li,Na,K) clusters for n

PubMed

Hernández-Rojas, J; Bretón, J; Gomez Llorente, J M; Wales, D J

2004-12-22

Basin-hopping global optimization is used to find likely candidates for the lowest minima on the potential energy surface of (C(60))(n)X (X=Li(+),Na(+),K(+),Cl(-)) and (C(60))(n)YCl (Y=Li,Na,K) clusters with n

Minimum airflow reset of single-duct VAV terminal boxes

NASA Astrophysics Data System (ADS)

Cho, Young-Hum

Single duct Variable Air Volume (VAV) systems are currently the most widely used type of HVAC system in the United States. When installing such a system, it is critical to determine the minimum airflow set point of the terminal box, as an optimally selected set point will improve the level of thermal comfort and indoor air quality (IAQ) while at the same time lower overall energy costs. In principle, this minimum rate should be calculated according to the minimum ventilation requirement based on ASHRAE standard 62.1 and maximum heating load of the zone. Several factors must be carefully considered when calculating this minimum rate. Terminal boxes with conventional control sequences may result in occupant discomfort and energy waste. If the minimum rate of airflow is set too high, the AHUs will consume excess fan power, and the terminal boxes may cause significant simultaneous room heating and cooling. At the same time, a rate that is too low will result in poor air circulation and indoor air quality in the air-conditioned space. Currently, many scholars are investigating how to change the algorithm of the advanced VAV terminal box controller without retrofitting. Some of these controllers have been found to effectively improve thermal comfort, indoor air quality, and energy efficiency. However, minimum airflow set points have not yet been identified, nor has controller performance been verified in confirmed studies. In this study, control algorithms were developed that automatically identify and reset terminal box minimum airflow set points, thereby improving indoor air quality and thermal comfort levels, and reducing the overall rate of energy consumption. A theoretical analysis of the optimal minimum airflow and discharge air temperature was performed to identify the potential energy benefits of resetting the terminal box minimum airflow set points. Applicable control algorithms for calculating the ideal values for the minimum airflow reset were developed and applied to actual systems for performance validation. The results of the theoretical analysis, numeric simulations, and experiments show that the optimal control algorithms can automatically identify the minimum rate of heating airflow under actual working conditions. Improved control helps to stabilize room air temperatures. The vertical difference in the room air temperature was lower than the comfort value. Measurements of room CO2 levels indicate that when the minimum airflow set point was reduced it did not adversely affect the indoor air quality. According to the measured energy results, optimal control algorithms give a lower rate of reheating energy consumption than conventional controls.

Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Austin; Beiter, Philipp; Heimiller, Donna

The report describes a geospatial analysis method to estimate the economic potential of several renewable resources available for electricity generation in the United States. Economic potential, one measure of renewable generation potential, is defined in this report as the subset of the available resource technical potential where the cost required to generate the electricity (which determines the minimum revenue requirements for development of the resource) is below the revenue available in terms of displaced energy and displaced capacity.

Creosote bush (Larrea tridentata) resin increases water demands and reduces energy availability in desert woodrats (Neotoma lepida).

PubMed

Mangione, Antonio M; Dearing, M Denise; Karasov, William H

2004-07-01

Although many plant secondary compounds are known to have serious consequences for herbivores, the costs of processing them are generally unknown. Two potential costs of ingestion and detoxification of secondary compounds are elevation of the minimum drinking water requirement and excretion of energetically expensive metabolites (i.e., glucuronides) in the urine. To address these impacts, we studied the costs of ingestion of resin from creosote bush (Larrea tridentata) on desert woodrats (Neotoma lepida). The following hypotheses were tested: ingestion of creosote resin by woodrats (1) increases minimum water requirement and (2) reduces energy available by increasing fecal and urinary energy losses. We tested the first hypothesis, by measuring the minimum water requirement of woodrats fed a control diet with and without creosote resin. Drinking water was given in decreasing amounts until woodrats could no longer maintain constant body mass. In two separate experiments, the minimum drinking water requirement of woodrats fed resin was higher than that of controls by 18-30% (about 1-1.7 ml/d). We tested several potential mechanisms of increased water loss associated with the increase in water requirement. The rate of fecal water loss was higher in woodrats consuming resin. Neither urinary water nor evaporative water loss was affected by ingestion of resin. Hypothesis 2 was tested by measuring energy fluxes of woodrats consuming control vs. resin-treated diets. Woodrats on a resin diet had higher urinary energy losses and, thus, metabolized a lower proportion of the dietary energy than did woodrats on control diet. Fecal energy excretion was not affected by resin. The excretion of glucuronic acid represented almost half of the energy lost as a consequence of resin ingestion. The increased water requirement and energy losses of woodrats consuming a diet with resin could have notable ecological consequences.

Energy Balance for a Sonoluminescence Bubble Yields a Measure of Ionization Potential Lowering

NASA Astrophysics Data System (ADS)

Kappus, B.; Bataller, A.; Putterman, S. J.

2013-12-01

Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization >36%. Analysis reveals only 2.1±0.6eV/atom of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

Energy balance for a sonoluminescence bubble yields a measure of ionization potential lowering.

PubMed

Kappus, B; Bataller, A; Putterman, S J

2013-12-06

Application of energy conservation between input sound and the microplasma which forms at the moment of sonoluminescence places bounds on the process, whereby the gas is ionized. Detailed pulsed Mie scattering measurements of the radius versus time for a xenon bubble in sulfuric acid provide a complete characterization of the hydrodynamics and minimum radius. For a range of emission intensities, the blackbody spectrum emitted during collapse matches the minimum bubble radius, implying opaque conditions are attained. This requires a degree of ionization >36%. Analysis reveals only 2.1±0.6  eV/atom of energy available during light emission. In order to unbind enough charge, collective processes must therefore reduce the ionization potential by at least 75%. We interpret this as evidence that a phase transition to a highly ionized plasma is occurring during sonoluminescence.

N(2)O in small para-hydrogen clusters: Structures and energetics.

PubMed

Zhu, Hua; Xie, Daiqian

2009-04-30

We present the minimum-energy structures and energetics of clusters of the linear N(2)O molecule with small numbers of para-hydrogen molecules with pairwise additive potentials. Interaction energies of (p-H(2))-N(2)O and (p-H(2))-(p-H(2)) complexes were calculated by averaging the corresponding full-dimensional potentials over the H(2) angular coordinates. The averaged (p-H(2))-N(2)O potential has three minima corresponding to the T-shaped and the linear (p-H(2))-ONN and (p-H(2))-NNO structures. Optimization of the minimum-energy structures was performed using a Genetic Algorithm. It was found that p-H(2) molecules fill three solvation rings around the N(2)O axis, each of them containing up to five p-H(2) molecules, followed by accumulation of two p-H(2) molecules at the oxygen and nitrogen ends. The first solvation shell is completed at N = 17. The calculated chemical potential oscillates with cluster size up to the completed first solvation shell. These results are consistent with the available experimental measurements. (c) 2009 Wiley Periodicals, Inc.

Quadratic String Method for Locating Instantons in Tunneling Splitting Calculations.

PubMed

Cvitaš, Marko T

2018-03-13

The ring-polymer instanton (RPI) method is an efficient technique for calculating approximate tunneling splittings in high-dimensional molecular systems. In the RPI method, tunneling splitting is evaluated from the properties of the minimum action path (MAP) connecting the symmetric wells, whereby the extensive sampling of the full potential energy surface of the exact quantum-dynamics methods is avoided. Nevertheless, the search for the MAP is usually the most time-consuming step in the standard numerical procedures. Recently, nudged elastic band (NEB) and string methods, originaly developed for locating minimum energy paths (MEPs), were adapted for the purpose of MAP finding with great efficiency gains [ J. Chem. Theory Comput. 2016 , 12 , 787 ]. In this work, we develop a new quadratic string method for locating instantons. The Euclidean action is minimized by propagating the initial guess (a path connecting two wells) over the quadratic potential energy surface approximated by means of updated Hessians. This allows the algorithm to take many minimization steps between the potential/gradient calls with further reductions in the computational effort, exploiting the smoothness of potential energy surface. The approach is general, as it uses Cartesian coordinates, and widely applicable, with computational effort of finding the instanton usually lower than that of determining the MEP. It can be combined with expensive potential energy surfaces or on-the-fly electronic-structure methods to explore a wide variety of molecular systems.

Adaptive Particle Swarm Optimizer with Varying Acceleration Coefficients for Finding the Most Stable Conformer of Small Molecules.

PubMed

Agrawal, Shikha; Silakari, Sanjay; Agrawal, Jitendra

2015-11-01

A novel parameter automation strategy for Particle Swarm Optimization called APSO (Adaptive PSO) is proposed. The algorithm is designed to efficiently control the local search and convergence to the global optimum solution. Parameters c1 controls the impact of the cognitive component on the particle trajectory and c2 controls the impact of the social component. Instead of fixing the value of c1 and c2 , this paper updates the value of these acceleration coefficients by considering time variation of evaluation function along with varying inertia weight factor in PSO. Here the maximum and minimum value of evaluation function is use to gradually decrease and increase the value of c1 and c2 respectively. Molecular energy minimization is one of the most challenging unsolved problems and it can be formulated as a global optimization problem. The aim of the present paper is to investigate the effect of newly developed APSO on the highly complex molecular potential energy function and to check the efficiency of the proposed algorithm to find the global minimum of the function under consideration. The proposed algorithm APSO is therefore applied in two cases: Firstly, for the minimization of a potential energy of small molecules with up to 100 degrees of freedom and finally for finding the global minimum energy conformation of 1,2,3-trichloro-1-flouro-propane molecule based on a realistic potential energy function. The computational results of all the cases show that the proposed method performs significantly better than the other algorithms. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generic cosmic-censorship violation in anti-de Sitter space.

PubMed

Hertog, Thomas; Horowitz, Gary T; Maeda, Kengo

2004-04-02

We consider (four-dimensional) gravity coupled to a scalar field with potential V(phi). The potential satisfies the positive energy theorem for solutions that asymptotically tend to a negative local minimum. We show that for a large class of such potentials, there is an open set of smooth initial data that evolve to naked singularities. Hence cosmic censorship does not hold for certain reasonable matter theories in asymptotically anti-de Sitter spacetimes. The asymptotically flat case is more subtle. We suspect that potentials with a local Minkowski minimum may similarly lead to violations of cosmic censorship in asymptotically flat spacetimes, but we do not have definite results.

Inflation and dark energy from f(R) gravity

NASA Astrophysics Data System (ADS)

Artymowski, Michał; Lalak, Zygmunt

2014-09-01

The standard Starobinsky inflation has been extended to the R + α Rn - β R2-n model to obtain a stable minimum of the Einstein frame scalar potential of the auxiliary field. As a result we have obtained obtain a scalar potential with non-zero value of residual vacuum energy, which may be a source of Dark Energy. Our results can be easily consistent with PLANCK or BICEP2 data for appropriate choices of the value of n.

Self-organized minimum-energy structures for dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Kofod, G.; Paajanen, M.; Bauer, S.

2006-11-01

When a stretched elastomer is laminated to a flat plastic frame, a complex shape is formed, which is termed a minimum-energy structure. It is shown how self-organized structures can be applied in the development of actuators with complex, out-of-plane actuationmodes. This unusual concept is then demonstrated in the case of dielectric elastomer actuators. Among advantages of this approach are the simplicity in manufacturing, the potential complexity and sophistication of the manufactured structures, and the general benefits of the concept when applied to other electro-mechanically active materials.

The Fermi-Pasta-Ulam System as a Model for Glasses

NASA Astrophysics Data System (ADS)

Carati, A.; Maiocchi, A.; Galgani, L.; Amati, G.

2015-12-01

We show that the standard Fermi-Pasta-Ulam system, with a suitable choice for the interparticle potential, constitutes a model for glasses, and indeed an extremely simple and manageable one. Indeed, it allows one to describe the landscape of the minima of the potential energy and to deal concretely with any one of them, determining the spectrum of frequencies and the normal modes. A relevant role is played by the harmonic energy {E} relative to a given minimum, i.e., the expansion of the Hamiltonian about the minimum up to second order. Indeed we find that there exists an energy threshold in {E} such that below it the harmonic energy {E} appears to be an approximate integral of motion for the whole observation time. Consequently, the system remains trapped near the minimum, in what may be called a vitreous or glassy state. Instead, for larger values of {E} the system rather quickly relaxes to a final equilibrium state. Moreover we find that the vitreous states present peculiar statistical behaviors, still involving the harmonic energy {E}. Indeed, the vitreous states are described by a Gibbs distribution with an effective Hamiltonian close to {E} and with a suitable effective inverse temperature. The final equilibrium state presents instead statistical properties which are in very good agreement with the Gibbs distribution relative to the full Hamiltonian of the system.

EFFECT OF STRAIN FIELD ON THRESHOLD DISPLACEMENT ENERGY OF TUNGSTEN STUDIED BY MOLECULAR DYNAMICS SIMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, D.; Gao, Ning; Setyawan, Wahyu

The influence of hydrostatic strain on point defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten was studied with molecular dynamics simulations. Two different tungsten potentials (Fikar and Juslin) were used. The minimum Ed direction calculated with the Fikar-potential was <100>, but with the Juslin-potential it was <111>. The most stable self-interstitial (SIA) configuration was a <111>-crowdion for both potentials. The stable SIA configuration did not change with applied strain. Varying the strain from compression to tension increased the vacancy formation energy but decreased the SIA formation energy. The SIA formation energy changed more significantly thanmore » for a vacancy such that Ed decreased with applied strain from compression to tension.« less

Bifurcations on Potential Energy Surfaces of Organic Reactions

PubMed Central

Ess, Daniel H.; Wheeler, Steven E.; Iafe, Robert G.; Xu, Lai; Çelebi-Ölçüm, Nihan; Houk, K. N.

2009-01-01

A single transition state may lead to multiple intermediates or products if there is a post-transition state reaction path bifurcation. These bifurcations arise when there are sequential transition states with no intervening energy minimum. For such systems, the shape of the potential energy surface and dynamic effects control selectivity rather than transition state energetics. This minireview covers recent investigations of organic reactions exhibiting reaction pathway bifurcations. Such phenomena are surprisingly general and affect experimental observables such as kinetic isotope effects and product distributions. PMID:18767086

Determining Equilibrium Position For Acoustical Levitation

NASA Technical Reports Server (NTRS)

Barmatz, M. B.; Aveni, G.; Putterman, S.; Rudnick, J.

1989-01-01

Equilibrium position and orientation of acoustically-levitated weightless object determined by calibration technique on Earth. From calibration data, possible to calculate equilibrium position and orientation in presence of Earth gravitation. Sample not levitated acoustically during calibration. Technique relies on Boltzmann-Ehrenfest adiabatic-invariance principle. One converts resonant-frequency-shift data into data on normalized acoustical potential energy. Minimum of energy occurs at equilibrium point. From gradients of acoustical potential energy, one calculates acoustical restoring force or torque on objects as function of deviation from equilibrium position or orientation.

A hierarchical approach for the design improvements of an Organocat biorefinery.

PubMed

Abdelaziz, Omar Y; Gadalla, Mamdouh A; El-Halwagi, Mahmoud M; Ashour, Fatma H

2015-04-01

Lignocellulosic biomass has emerged as a potentially attractive renewable energy source. Processing technologies of such biomass, particularly its primary separation, still lack economic justification due to intense energy requirements. Establishing an economically viable and energy efficient biorefinery scheme is a significant challenge. In this work, a systematic approach is proposed for improving basic/existing biorefinery designs. This approach is based on enhancing the efficiency of mass and energy utilization through the use of a hierarchical design approach that involves mass and energy integration. The proposed procedure is applied to a novel biorefinery called Organocat to minimize its energy and mass consumption and total annualized cost. An improved heat exchanger network with minimum energy consumption of 4.5 MJ/kgdry biomass is designed. An optimal recycle network with zero fresh water usage and minimum waste discharge is also constructed, making the process more competitive and economically attractive. Copyright © 2015 Elsevier Ltd. All rights reserved.

Minimum energy control for in vitro neurons.

PubMed

Nabi, Ali; Stigen, Tyler; Moehlis, Jeff; Netoff, Theoden

2013-06-01

To demonstrate the applicability of optimal control theory for designing minimum energy charge-balanced input waveforms for single periodically-firing in vitro neurons from brain slices of Long-Evans rats. The method of control uses the phase model of a neuron and does not require prior knowledge of the neuron's biological details. The phase model of a neuron is a one-dimensional model that is characterized by the neuron's phase response curve (PRC), a sensitivity measure of the neuron to a stimulus applied at different points in its firing cycle. The PRC for each neuron is experimentally obtained by measuring the shift in phase due to a short-duration pulse injected into the periodically-firing neuron at various phase values. Based on the measured PRC, continuous-time, charge-balanced, minimum energy control waveforms have been designed to regulate the next firing time of the neuron upon application at the onset of an action potential. The designed waveforms can achieve the inter-spike-interval regulation for in vitro neurons with energy levels that are lower than those of conventional monophasic pulsatile inputs of past studies by at least an order of magnitude. They also provide the advantage of being charge-balanced. The energy efficiency of these waveforms is also shown by performing several supporting simulations that compare the performance of the designed waveforms against that of phase shuffled surrogate inputs, variants of the minimum energy waveforms obtained from suboptimal PRCs, as well as pulsatile stimuli that are applied at the point of maximum PRC. It was found that the minimum energy waveforms perform better than all other stimuli both in terms of control and in the amount of energy used. Specifically, it was seen that these charge-balanced waveforms use at least an order of magnitude less energy than conventional monophasic pulsatile stimuli. The significance of this work is that it uses concepts from the theory of optimal control and introduces a novel approach in designing minimum energy charge-balanced input waveforms for neurons that are robust to noise and implementable in electrophysiological experiments.

Minimum energy control for in vitro neurons

NASA Astrophysics Data System (ADS)

Nabi, Ali; Stigen, Tyler; Moehlis, Jeff; Netoff, Theoden

2013-06-01

Objective. To demonstrate the applicability of optimal control theory for designing minimum energy charge-balanced input waveforms for single periodically-firing in vitro neurons from brain slices of Long-Evans rats. Approach. The method of control uses the phase model of a neuron and does not require prior knowledge of the neuron’s biological details. The phase model of a neuron is a one-dimensional model that is characterized by the neuron’s phase response curve (PRC), a sensitivity measure of the neuron to a stimulus applied at different points in its firing cycle. The PRC for each neuron is experimentally obtained by measuring the shift in phase due to a short-duration pulse injected into the periodically-firing neuron at various phase values. Based on the measured PRC, continuous-time, charge-balanced, minimum energy control waveforms have been designed to regulate the next firing time of the neuron upon application at the onset of an action potential. Main result. The designed waveforms can achieve the inter-spike-interval regulation for in vitro neurons with energy levels that are lower than those of conventional monophasic pulsatile inputs of past studies by at least an order of magnitude. They also provide the advantage of being charge-balanced. The energy efficiency of these waveforms is also shown by performing several supporting simulations that compare the performance of the designed waveforms against that of phase shuffled surrogate inputs, variants of the minimum energy waveforms obtained from suboptimal PRCs, as well as pulsatile stimuli that are applied at the point of maximum PRC. It was found that the minimum energy waveforms perform better than all other stimuli both in terms of control and in the amount of energy used. Specifically, it was seen that these charge-balanced waveforms use at least an order of magnitude less energy than conventional monophasic pulsatile stimuli. Significance. The significance of this work is that it uses concepts from the theory of optimal control and introduces a novel approach in designing minimum energy charge-balanced input waveforms for neurons that are robust to noise and implementable in electrophysiological experiments.

Simulation of Collision of Arbitrary Shape Particles with Wall in a Viscous Fluid

NASA Astrophysics Data System (ADS)

Mohaghegh, Fazlolah; Udaykumar, H. S.

2016-11-01

Collision of finite size arbitrary shape particles with wall in a viscous flow is modeled using immersed boundary method. A potential function indicating the distance from the interface is introduced for the particles and the wall. The potential can be defined by using either an analytical expression or level set method. The collision starts when the indicator potentials of the particle and wall are overlapping based on a minimum cut off. A simplified mass spring model is used in order to apply the collision forces. Instead of using a dashpot in order to damp the energy, the spring stiffness is adjusted during the bounce. The results for the case of collision of a falling sphere with the bottom wall agrees well with the experiments. Moreover, it is shown that the results are independent from the minimum collision cut off distance value. Finally, when the particle's shape is ellipsoidal, the rotation of the particle after the collision becomes important and noticeable: At low Stokes number values, the particle almost adheres to the wall in one side and rotates until it reaches the minimum gravitational potential. At high Stokes numbers, the particle bounces and loses the energy until it reaches a situation with low Stokes number.

Comparison of Degrees of Potential-Energy-Surface Anharmonicity for Complexes and Clusters with Hydrogen Bonds

NASA Astrophysics Data System (ADS)

Kozlovskaya, E. N.; Doroshenko, I. Yu.; Pogorelov, V. E.; Vaskivskyi, Ye. V.; Pitsevich, G. A.

2018-01-01

Previously calculated multidimensional potential-energy surfaces of the MeOH monomer and dimer, water dimer, malonaldehyde, formic acid dimer, free pyridine-N-oxide/trichloroacetic acid complex, and protonated water dimer were analyzed. The corresponding harmonic potential-energy surfaces near the global minima were constructed for series of clusters and complexes with hydrogen bonds of different strengths based on the behavior of the calculated multidimensional potential-energy surfaces. This enabled the introduction of an obvious anharmonicity parameter for the calculated potential-energy surfaces. The anharmonicity parameter was analyzed as functions of the size of the analyzed area near the energy minimum, the number of points over which energies were compared, and the dimensionality of the solved vibrational problem. Anharmonicity parameters for potential-energy surfaces in complexes with strong, medium, and weak H-bonds were calculated under identical conditions. The obtained anharmonicity parameters were compared with the corresponding diagonal anharmonicity constants for stretching vibrations of the bridging protons and the lengths of the hydrogen bridges.

New chemical sources of energy: A theoretical study

NASA Astrophysics Data System (ADS)

Chaban, Galina

The research presented in this dissertation employs methods of quantum chemistry for the search of highly energetic chemical compounds that can have applications as possible energy sources. The areas of research include: (1) improvement of orbital optimization methods for different types of wavefunctions which leads to substantial savings of computer time and memory; (2) predicting new high energy isomers for singlet and triplet states of Nsb3F and their kinetic stability with respect to isomerisation and dissociation reactions; (3) estimation of minimum energy reaction paths for dissociation reactions of high energy isomers of Nsb2Osb2 including potential energy barriers and minimum energy crossing points between the closest singlet and triplet states; (4) investigation of thermodynamic and kinetic stability of Van der Waals complexes M-Hsb2 (M = Li, Be, B, C, Na, Mg, Al, Si) that can play an important role in improvement of energetic properties of hydrogen based rocket fuels; (5) mapping of the potential energy surface for AlHsb2 compound in the region of crossing between sp2Bsb2 and sp2Asb1 electronic states and predicting the kinetic stability of Al complex, which suggests that Al may be among the promising candidates for inclusion into solid hydrogen for the purpose of energy storage.

Table of superdeformed nuclear bands and fission isomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firestone, R.B.; Singh, B.

A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in {sup 152}Dy was predicted for {beta}{sub 2}-0.65. Subsequently, a discrete set of {gamma}-ray transitions in {sup 152}DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of {gamma}-ray detector arrays is already producing a wealth of information about the mechanisms for feeding andmore » deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra.« less

Energy landscapes and properties of biomolecules.

PubMed

Wales, David J

2005-11-09

Thermodynamic and dynamic properties of biomolecules can be calculated using a coarse-grained approach based upon sampling stationary points of the underlying potential energy surface. The superposition approximation provides an overall partition function as a sum of contributions from the local minima, and hence functions such as internal energy, entropy, free energy and the heat capacity. To obtain rates we must also sample transition states that link the local minima, and the discrete path sampling method provides a systematic means to achieve this goal. A coarse-grained picture is also helpful in locating the global minimum using the basin-hopping approach. Here we can exploit a fictitious dynamics between the basins of attraction of local minima, since the objective is to find the lowest minimum, rather than to reproduce the thermodynamics or dynamics.

Principles of time evolution in classical physics

NASA Astrophysics Data System (ADS)

Güémez, J.; Fiolhais, M.

2018-07-01

We address principles of time evolution in classical mechanical/thermodynamical systems in translational and rotational motion, in three cases: when there is conservation of mechanical energy, when there is energy dissipation and when there is mechanical energy production. In the first case, the time derivative of the Hamiltonian vanishes. In the second one, when dissipative forces are present, the time evolution is governed by the minimum potential energy principle, or, equivalently, maximum increase of the entropy of the universe. Finally, in the third situation, when internal sources of work are available to the system, it evolves in time according to the principle of minimum Gibbs function. We apply the Lagrangian formulation to the systems, dealing with the non-conservative forces using restriction functions such as the Rayleigh dissipative function.

Cavity Born-Oppenheimer Approximation for Correlated Electron-Nuclear-Photon Systems.

PubMed

Flick, Johannes; Appel, Heiko; Ruggenthaler, Michael; Rubio, Angel

2017-04-11

In this work, we illustrate the recently introduced concept of the cavity Born-Oppenheimer approximation [ Flick et al. PNAS 2017 , 10.1073/pnas.1615509114 ] for correlated electron-nuclear-photon problems in detail. We demonstrate how an expansion in terms of conditional electronic and photon-nuclear wave functions accurately describes eigenstates of strongly correlated light-matter systems. For a GaAs quantum ring model in resonance with a photon mode we highlight how the ground-state electronic potential-energy surface changes the usual harmonic potential of the free photon mode to a dressed mode with a double-well structure. This change is accompanied by a splitting of the electronic ground-state density. For a model where the photon mode is in resonance with a vibrational transition, we observe in the excited-state electronic potential-energy surface a splitting from a single minimum to a double minimum. Furthermore, for a time-dependent setup, we show how the dynamics in correlated light-matter systems can be understood in terms of population transfer between potential energy surfaces. This work at the interface of quantum chemistry and quantum optics paves the way for the full ab initio description of matter-photon systems.

Ground and excited states of vanadium hydroxide isomers and their cations, VOH0,+ and HVO0,+

NASA Astrophysics Data System (ADS)

Miliordos, Evangelos; Harrison, James F.; Hunt, Katharine L. C.

2013-03-01

Employing correlation consistent basis sets of quadruple-zeta quality and applying both multireference configuration interaction and single-reference coupled cluster methodologies, we studied the electronic and geometrical structure of the [V,O,H]0,+ species. The electronic structure of HVO0,+ is explained by considering a hydrogen atom approaching VO0,+, while VOH0,+ molecules are viewed in terms of the interaction of V+,2+ with OH-. The potential energy curves for H-VO0,+ and V0,+-OH have been constructed as functions of the distance between the interacting subunits, and the potential energy curves have also been determined as functions of the H-V-O angle. For the stationary points that we have located, we report energies, geometries, harmonic frequencies, and dipole moments. We find that the most stable bent HVO0,+ structure is lower in energy than any of the linear HVO0,+ structures. Similarly, the most stable state of bent VOH is lower in energy than the linear structures, but linear VOH+ is lower in energy than bent VOH+. The global minimum on the potential energy surface for the neutral species is the tilde{X}^3A″ state of bent HVO, although the tilde{X}^5A″ state of bent VOH is less than 5 kcal/mol higher in energy. The global minimum on the potential surface for the cation is the tilde{X}^4Σ ^- state of linear VOH+, with bent VOH+ and bent HVO+ both more than 10 kcal/mol higher in energy. For the neutral species, the bent geometries exhibit significantly higher dipole moments than the linear structures.

Preferential flow, connectivity and the principle of "minimum time to equilibrium": a new perspective on environmental water flow

NASA Astrophysics Data System (ADS)

Zehe, E.; Blume, T.; Bloeschl, G.

2008-12-01

Preferential/rapid flow and transport is known as one key process in soil hydrology for more than 20 years. It seems to be rather the rule, than the exception. It occurs in soils, in surface rills and river networks. If connective preferential are present at any scale, they crucially control water flow and solute transport. Why? Is there an underlying principle? If energy is conserved a system follows Fermat's principle of minimum action i.e. it follows the trajectory that minimise the integral of the total energy/ La Grangian over time. Hydrological systems are, however, non-conservative as surface and subsurface water flows dissipate energy. From thermodynamics it is well known that natural processes minimize the free energy of the system. For hydrological systems we suggest, therefore, that flow in a catchment arranges in such a way that time to a minimum of free energy becomes minimal for a given rainfall input (disturbance) and under given constraints. Free energy in a soil is determined by potential energy and capillary energy. The pore size distribution of the soil, soil structures, depth to groundwater and most important vegetation make up the constraints. The pore size distribution determines whether potential energy or capillarity dominates the free energy of the soil system. The first term is minimal when the pore space is completely de-saturated the latter becomes minimal at soil saturation. Hence, the soil determines a) the amount of excess (gravity) water that has to be exported from the soil to reach a minimum state of free energy and b) whether redistribution or groundwater recharge is more efficient to reach that equilibrium. On the other hand, the pore size distribution of the soil and the connectivity of preferential pathways (root channels, worm holes and cracks) determine flow velocities and the redistribution of water within the pore space. As water flow and ground water recharge are fast in sandy soils and capillary energy is of minor importance, connective preferential pathways do not mean any advantage for an efficient transition to an equilibrium in these systems. In fine grained soils Darcy velocities and therefore redistribution of water is 2-4 orders of magnitude slower. As capillary energy dominates in these soils an effective redistribution of water within the pore space is crucial for a fast transition of system to an equilibrium state. Connective preferential pathways ore even cracks allow a faster redistribution of water and seem therefore necessary for a fast transition into a state of minimum free energy. The suggested principle "of minimum time to equilibrium" may explain the "advantage" of preferential flow as a much more efficient dissipation of energy in fine grained soils and therefore why connective preferential pathways control environmental flow. From a fundamental, long term perspective the principle may help us to understand whether and why soil structures and even cracks evolve in different landscapes and climates and b) to link soil hydrology and (landscape) ecology. Along the lines the proposed study will present model results to test the stated hypothesis.

Absolute vibrational numbering from isotope shifts in fragmentary spectroscopic data

NASA Astrophysics Data System (ADS)

Pashov, A.; Kowalczyk, P.; Jastrzebski, W.

2018-05-01

We discuss application of the isotope effect to establish the absolute vibrational numbering in electronic states of diatomic molecules. This is illustrated by examples of states with potential energy curves of both regular and irregular shape, with one or two potential minima. The minimum number of spectroscopic data (either term values or spectral line positions) necessary to provide a unique numbering is considered. We show that at favourable conditions just four term energies (or spectral lines) in one isotopologue and one term energy in the other suffice.

Computed Potential Energy Surfaces and Minimum Energy Pathway for Chemical Reactions

NASA Technical Reports Server (NTRS)

Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

1994-01-01

Computed potential energy surfaces are often required for computation of such observables as rate constants as a function of temperature, product branching ratios, and other detailed properties. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method with the Dunning correlation consistent basis sets to obtain accurate energetics, gives useful results for a number of chemically important systems. Applications to complex reactions leading to NO and soot formation in hydrocarbon combustion are discussed.

Methanol clusters (CH3OH)n: putative global minimum-energy structures from model potentials and dispersion-corrected density functional theory.

PubMed

Kazachenko, Sergey; Bulusu, Satya; Thakkar, Ajit J

2013-06-14

Putative global minima are reported for methanol clusters (CH3OH)n with n ≤ 15. The predictions are based on global optimization of three intermolecular potential energy models followed by local optimization and single-point energy calculations using two variants of dispersion-corrected density functional theory. Recurring structural motifs include folded and/or twisted rings, folded rings with a short branch, and stacked rings. Many of the larger structures are stabilized by weak C-H···O bonds.

Estimate of Cost-Effective Potential for Minimum Efficiency Performance Standards in 13 Major World Economies Energy Savings, Environmental and Financial Impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Letschert, Virginie E.; Bojda, Nicholas; Ke, Jing

2012-07-01

This study analyzes the financial impacts on consumers of minimum efficiency performance standards (MEPS) for appliances that could be implemented in 13 major economies around the world. We use the Bottom-Up Energy Analysis System (BUENAS), developed at Lawrence Berkeley National Laboratory (LBNL), to analyze various appliance efficiency target levels to estimate the net present value (NPV) of policies designed to provide maximum energy savings while not penalizing consumers financially. These policies constitute what we call the “cost-effective potential” (CEP) scenario. The CEP scenario is designed to answer the question: How high can we raise the efficiency bar in mandatory programsmore » while still saving consumers money?« less

Effects of Energy Dissipation in the Sphere-Restricted Full Three-Body Problem

NASA Astrophysics Data System (ADS)

Gabriel, T. S. J.

Recently, the classical N-Body Problem has been adjusted to account for celestial bodies made of constituents of finite density. By imposing a minima on the achievable distance between particles, minimum energy resting states are allowed by the problem. The Full N-Body Problem allows for the dissipation of mechanical energy through surface-surface interactions via impacts or by way of tidal deformation. Barring exogeneous forces and allowing for the dissipation of energy, these systems have discrete, and sometimes multiple, minimum energy states for a given angular momentum. Building the dynamical framework of such finite density systems is a necessary process in outlining the evolution of rubble pile asteroids and other gravitational-granular systems such as protoplanetary discs, and potentially planetary rings, from a theoretical point of view. In all cases, resting states are expected to occur as a necessary step in the ongoing processes of solar system formation and evolution. Previous studies of this problem have been performed in the N=3 case where the bodies are indistinguishable spheres, with all possible relative equilibria and their stability having been identified as a function of the angular momentum of the system. These studies uncovered that at certain levels of angular momentum there exists two minimum energy states, a global and local minimum. Thus a question of interest is in which of these states a dissipative system would preferentially settle and the sensitivity of results to changes in dissipation parameters. Assuming equal-sized, perfectly-rigid bodies, this study investigates the dynamical evolution of three spheres under the influence of mutual gravity and impact mechanics as a function of dissipation parameters. A purpose-written, C-based, Hard Sphere Discrete Element Method code has been developed to integrate trajectories and resolve contact mechanics as grains evolve into minimum energy configurations. By testing many randomized initial conditions, statistics are measured regarding minimum energy states for a given angular momentum range. A trend in the Sphere-Restricted Full Three-Body Problem producing an end state of one configuration over another is found as a function of angular momentum and restitution.

Ab initio study of the CO-N2 complex: a new highly accurate intermolecular potential energy surface and rovibrational spectrum.

PubMed

Cybulski, Hubert; Henriksen, Christian; Dawes, Richard; Wang, Xiao-Gang; Bora, Neha; Avila, Gustavo; Carrington, Tucker; Fernández, Berta

2018-05-09

A new, highly accurate ab initio ground-state intermolecular potential-energy surface (IPES) for the CO-N2 complex is presented. Thousands of interaction energies calculated with the CCSD(T) method and Dunning's aug-cc-pVQZ basis set extended with midbond functions were fitted to an analytical function. The global minimum of the potential is characterized by an almost T-shaped structure and has an energy of -118.2 cm-1. The symmetry-adapted Lanczos algorithm was used to compute rovibrational energies (up to J = 20) on the new IPES. The RMSE with respect to experiment was found to be on the order of 0.038 cm-1 which confirms the very high accuracy of the potential. This level of agreement is among the best reported in the literature for weakly bound systems and considerably improves on those of previously published potentials.

Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dong; Gao, Ning; Setyawan, W.

The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten (W) has been studied with molecular dynamics simulations. Two different W potentials (Fikar and Juslin) were compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affects the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar-potential is <100> and with the Juslin-potential is <111>. Nevertheless, the most stable self-interstitial configuration is found to be a <111>-crowdion for both potentials. This stable configuration doesmore » not change with applied strain. Varying the strain from compression to tension increases the vacancy formation energy but decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with applied hydrostatic strain from compression to tension.« less

Equilibrium structure and atomic vibrations of Nin clusters

NASA Astrophysics Data System (ADS)

Borisova, Svetlana D.; Rusina, Galina G.

2017-12-01

The equilibrium bond lengths and binding energy, second differences in energy and vibrational frequencies of free clusters Nin (2 ≤ n ≤ 20) were calculated with the use of the interaction potential obtained in the tight-binding approximation (TBA). The results show that the minimum vibration frequency plays a significant role in the evaluation of the dynamic stability of the clusters. A nonmonotonic dependence of the minimum vibration frequency of clusters on their size and the extreme values for the number of atoms in a cluster n = 4, 6, 13, and 19 are demonstrated. This result agrees with the theoretical and experimental data on stable structures of small metallic clusters.

Theoretical study of the C-H/O-H stretching vibrations in malonaldehyde

NASA Astrophysics Data System (ADS)

Pitsevich, G. A.; Malevich, A. E.; Kozlovskaya, E. N.; Doroshenko, I. Yu.; Pogorelov, V. E.; Sablinskas, V.; Balevicius, V.

2015-06-01

IR and Raman spectra of the malonaldehyde molecule and its deuterated analogues were calculated in the B3LYP/cc-pVQZ approximation. Anharmonicity effects were taken into account both in the context of a standard model of the second order perturbation theory and by constructing the potential energy surfaces (PES) with a limited number of dimensions using the Cartesian coordinates of the hydroxyl hydrogen atom and the stretching coordinates of С-Н, C-D, O-H, and O-D bonds. It was shown that in each of the two equivalent forms of the molecule, besides the global minimum, an additional local minimum at the PES is formed with the energy more than 3000 cm-1 higher than the energy in the global minimum. Calculations carried out by constructing the 2D and 3D PESs indicate a high anharmonicity level and multiple manifestations of the stretching О-Н vibrations, despite the fact that the model used does not take into account the splitting of the ground-state and excited vibrational energy levels. In particular, the vibration with the frequency 3258 cm-1 may be associated with proton transfer to the region of a local minimum of energy. Comparing the results obtained with the experimental data presented in the literature allowed us to propose a new variant of bands assignments in IR and Raman spectra of the molecule in the spectral region 2500-3500 cm-1.

Taboo search by successive confinement: Surveying a potential energy surface

NASA Astrophysics Data System (ADS)

Chekmarev, Sergei F.

2001-09-01

A taboo search for minima on a potential energy surface (PES) is performed by means of confinement molecular dynamics: the molecular dynamics trajectory of the system is successively confined to various basins on the PES that have not been sampled yet. The approach is illustrated for a 13-atom Lennard-Jones cluster. It is shown that the taboo search radically accelerates the process of surveying the PES, with the probability of finding a new minimum defined by a propagating Fermi-like distribution.

Optical properties of InAs/GaAs quantum dot superlattice structures

NASA Astrophysics Data System (ADS)

Imran, Ali; Jiang, Jianliang; Eric, Deborah; Zahid, M. Noaman; Yousaf, M.; Shah, Z. H.

2018-06-01

Quantum dot (QD) structure has potential applications in modern highly efficient optoelectronic devices due to their band-tuning. The device dimensions have been miniatured with increased efficiencies by virtue of this discovery. In this research, we have presented modified analytical and simulation results of InAs/GaAs QD superlattice (QDSL). We have applied tight binding model for the investigation of ground state energies using timeindependent Schrödinger equation (SE) with effective mass approximation. It has been investigated that the electron energies are confined due to wave function delocalization in closely coupled QD structures. The minimum ground state energy can be obtained by increasing the periodicity and decreasing the barrier layer thickness. We have calculated electronics and optical properties which includes ground state energies, transition energies, density of states (DOS), absorption coefficient and refractive index, which can be tuned by structure modification. In our results, the minimum ground state energy of QDSL is achieved to be 0.25 eV with a maximum period of 10 QDs. The minimum band to band and band to continuum transition energies are 63 meV and 130 meV with 2 nm barrier layer thickness respectively. The absorption coefficient of our proposed QDSL model is found to be maximum 1.2 × 104 cm-1 and can be used for highly sensitive infrared detector and high efficiency solar cells.

Tachyon cosmology with non-vanishing minimum potential: a unified model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Huiquan, E-mail: hqli@ustc.edu.cn

2012-07-01

We investigate the tachyon condensation process in the effective theory with non-vanishing minimum potential and its implications to cosmology. It is shown that the tachyon condensation on an unstable three-brane described by this modified tachyon field theory leads to lower-dimensional branes (defects) forming within a stable three-brane. Thus, in the cosmological background, we can get well-behaved tachyon matter after tachyon inflation, (partially) avoiding difficulties encountered in the original tachyon cosmological models. This feature also implies that the tachyon inflated and reheated universe is followed by a Chaplygin gas dark matter and dark energy universe. Hence, such an unstable three-brane behavesmore » quite like our universe, reproducing the key features of the whole evolutionary history of the universe and providing a unified description of inflaton, dark matter and dark energy in a very simple single-scalar field model.« less

The effect of photoelectrons on boom-satellite potential differences during electron beam ejection

NASA Technical Reports Server (NTRS)

Lai, Shu T.; Cohen, Herbert A.; Aggson, Thomas L.; Mcneil, William J.

1987-01-01

Data taken on the SCATHA satellite at geosynchronous altitudes during periods of electron beam ejection in sunlight showed that the potential difference between an electrically isolated boom and the satellite main body was a function of beam current, energy, and boom-sun angle. The potential difference decreased as the boom area illuminated by the sun increased; the maximum and minimum potential differences were measured when minimum and maximum boom areas, respectively, were exposed to the sun. It is shown that photoelectrons, created on the boom, could be engulfed in the electrostatic field of the highly charged satellite main body. Theoretical calculations made using a simple current balance model showed that these electrons could provide a substantial discharging current to the main body and cause the observed variations in the potential difference between the main body and the booms.

10 CFR 440.16 - Minimum program requirements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 3 2014-01-01 2014-01-01 false Minimum program requirements. 440.16 Section 440.16 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION WEATHERIZATION ASSISTANCE FOR LOW-INCOME PERSONS § 440.16 Minimum...) Families with children; (4) High residential energy users; and (5) Households with a high energy burden. (c...

10 CFR 440.16 - Minimum program requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 3 2012-01-01 2012-01-01 false Minimum program requirements. 440.16 Section 440.16 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION WEATHERIZATION ASSISTANCE FOR LOW-INCOME PERSONS § 440.16 Minimum...) Families with children; (4) High residential energy users; and (5) Households with a high energy burden. (c...

10 CFR 440.16 - Minimum program requirements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 3 2013-01-01 2013-01-01 false Minimum program requirements. 440.16 Section 440.16 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION WEATHERIZATION ASSISTANCE FOR LOW-INCOME PERSONS § 440.16 Minimum...) Families with children; (4) High residential energy users; and (5) Households with a high energy burden. (c...

Temperature lapse rates at restricted thermodynamic equilibrium. Part II: Saturated air and further discussions

NASA Astrophysics Data System (ADS)

Björnbom, Pehr

2016-03-01

In the first part of this work equilibrium temperature profiles in fluid columns with ideal gas or ideal liquid were obtained by numerically minimizing the column energy at constant entropy, equivalent to maximizing column entropy at constant energy. A minimum in internal plus potential energy for an isothermal temperature profile was obtained in line with Gibbs' classical equilibrium criterion. However, a minimum in internal energy alone for adiabatic temperature profiles was also obtained. This led to a hypothesis that the adiabatic lapse rate corresponds to a restricted equilibrium state, a type of state in fact discussed already by Gibbs. In this paper similar numerical results for a fluid column with saturated air suggest that also the saturated adiabatic lapse rate corresponds to a restricted equilibrium state. The proposed hypothesis is further discussed and amended based on the previous and the present numerical results and a theoretical analysis based on Gibbs' equilibrium theory.

New Approaches to Minimum-Energy Design of Integer- and Fractional-Order Perfect Control Algorithms

NASA Astrophysics Data System (ADS)

Hunek, Wojciech P.; Wach, Łukasz

2017-10-01

In this paper the new methods concerning the energy-based minimization of the perfect control inputs is presented. For that reason the multivariable integer- and fractional-order models are applied which can be used for describing a various real world processes. Up to now, the classical approaches have been used in forms of minimum-norm/least squares inverses. Notwithstanding, the above-mentioned tool do not guarantee the optimal control corresponding to optimal input energy. Therefore the new class of inversebased methods has been introduced, in particular the new σ- and H-inverse of nonsquare parameter and polynomial matrices. Thus a proposed solution remarkably outperforms the typical ones in systems where the control runs can be understood in terms of different physical quantities, for example heat and mass transfer, electricity etc. A simulation study performed in Matlab/Simulink environment confirms the big potential of the new energy-based approaches.

A general method for the derivation of the functional forms of the effective energy terms in coarse-grained energy functions of polymers. II. Backbone-local potentials of coarse-grained O 1 →4 -bonded polyglucose chains

NASA Astrophysics Data System (ADS)

Lubecka, Emilia A.; Liwo, Adam

2017-09-01

Based on the theory of the construction of coarse-grained force fields for polymer chains described in our recent work [A. K. Sieradzan et al., J. Chem. Phys. 146, 124106 (2017)], in this work effective coarse-grained potentials, to be used in the SUGRES-1P model of polysaccharides that is being developed in our laboratory, have been determined for the O ⋯O ⋯O virtual-bond angles (θ ) and for the dihedral angles for rotation about the O ⋯O virtual bonds (γ ) of 1 → 4 -linked glucosyl polysaccharides, for all possible combinations of [α ,β ]-[d,l]-glucose. The potentials of mean force corresponding to the virtual-bond angles and the virtual-bond dihedral angles were calculated from the free-energy surfaces of [α ,β ]-[d,l]-glucose pairs, determined by umbrella-sampling molecular-dynamics simulations with the AMBER12 force field, or combinations of the surfaces of two pairs sharing the overlapping residue, respectively, by integrating the respective Boltzmann factor over the dihedral angles λ for the rotation of the sugar units about the O ⋯O virtual bonds. Analytical expressions were subsequently fitted to the potentials of mean force. The virtual-bond-torsional potentials depend on both virtual-bond-dihedral angles and virtual-bond angles. The virtual-bond-angle potentials contain a single minimum at about θ =14 0° for all pairs except β -d-[α ,β ] -l-glucose, where the global minimum is shifted to θ =150° and a secondary minimum appears at θ =90°. The torsional potentials favor small negative γ angles for the α -d-glucose and extended negative angles γ for the β -d-glucose chains, as observed in the experimental structures of starch and cellulose, respectively. It was also demonstrated that the approximate expression derived based on Kubo's cluster-cumulant theory, whose coefficients depend on the identity of the disugar units comprising a trisugar unit that defines a torsional potential, fits simultaneously all torsional potentials very well, thus reducing the number of parameters significantly.

New analytical model for the ozone electronic ground state potential surface and accurate ab initio vibrational predictions at high energy range.

PubMed

Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A; Holka, Filip; Szalay, Péter G

2013-10-07

An accurate description of the complicated shape of the potential energy surface (PES) and that of the highly excited vibration states is of crucial importance for various unsolved issues in the spectroscopy and dynamics of ozone and remains a challenge for the theory. In this work a new analytical representation is proposed for the PES of the ground electronic state of the ozone molecule in the range covering the main potential well and the transition state towards the dissociation. This model accounts for particular features specific to the ozone PES for large variations of nuclear displacements along the minimum energy path. The impact of the shape of the PES near the transition state (existence of the "reef structure") on vibration energy levels was studied for the first time. The major purpose of this work was to provide accurate theoretical predictions for ozone vibrational band centres at the energy range near the dissociation threshold, which would be helpful for understanding the very complicated high-resolution spectra and its analyses currently in progress. Extended ab initio electronic structure calculations were carried out enabling the determination of the parameters of a minimum energy path PES model resulting in a new set of theoretical vibrational levels of ozone. A comparison with recent high-resolution spectroscopic data on the vibrational levels gives the root-mean-square deviations below 1 cm(-1) for ozone band centres up to 90% of the dissociation energy. New ab initio vibrational predictions represent a significant improvement with respect to all previously available calculations.

Challenging the cosmological constant

NASA Astrophysics Data System (ADS)

Kaloper, Nemanja

2007-09-01

We outline a dynamical dark energy scenario whose signatures may be simultaneously tested by astronomical observations and laboratory experiments. The dark energy is a field with slightly sub-gravitational couplings to matter, a logarithmic self-interaction potential with a scale tuned to ˜10 eV, as is usual in quintessence models, and an effective mass m influenced by the environmental energy density. Its forces may be suppressed just below the current bounds by the chameleon-like mimicry, whereby only outer layers of mass distributions, of thickness 1/m, give off appreciable long range forces. After inflation and reheating, the field is relativistic, and attains a Planckian expectation value before Hubble friction freezes it. This can make gravity in space slightly stronger than on Earth. During the matter era, interactions with nonrelativistic matter dig a minimum close to the Planck scale. However, due to its sub-gravitational matter couplings the field will linger away from this minimum until the matter energy density dips below ˜10 eV. Then it starts to roll to the minimum, driving a period of cosmic acceleration. Among the signatures of this scenario may be dark energy equation of state w≠-1, stronger gravity in dilute mediums, that may influence BBN and appear as an excess of dark matter, and sub-millimeter corrections to Newton's law, close to the present laboratory limits.

Quasi-static responses and variational principles in gradient plasticity

NASA Astrophysics Data System (ADS)

Nguyen, Quoc-Son

2016-12-01

Gradient models have been much discussed in the literature for the study of time-dependent or time-independent processes such as visco-plasticity, plasticity and damage. This paper is devoted to the theory of Standard Gradient Plasticity at small strain. A general and consistent mathematical description available for common time-independent behaviours is presented. Our attention is focussed on the derivation of general results such as the description of the governing equations for the global response and the derivation of related variational principles in terms of the energy and the dissipation potentials. It is shown that the quasi-static response under a loading path is a solution of an evolution variational inequality as in classical plasticity. The rate problem and the rate minimum principle are revisited. A time-discretization by the implicit scheme of the evolution equation leads to the increment problem. An increment of the response associated with a load increment is a solution of a variational inequality and satisfies also a minimum principle if the energy potential is convex. The increment minimum principle deals with stables solutions of the variational inequality. Some numerical methods are discussed in view of the numerical simulation of the quasi-static response.

Minimum separation distances for natural gas pipeline and boilers in the 300 area, Hanford Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daling, P.M.; Graham, T.M.

1997-08-01

The U.S. Department of Energy (DOE) is proposing actions to reduce energy expenditures and improve energy system reliability at the 300 Area of the Hanford Site. These actions include replacing the centralized heating system with heating units for individual buildings or groups of buildings, constructing a new natural gas distribution system to provide a fuel source for many of these units, and constructing a central control building to operate and maintain the system. The individual heating units will include steam boilers that are to be housed in individual annex buildings located at some distance away from nearby 300 Area nuclearmore » facilities. This analysis develops the basis for siting the package boilers and natural gas distribution systems to be used to supply steam to 300 Area nuclear facilities. The effects of four potential fire and explosion scenarios involving the boiler and natural gas pipeline were quantified to determine minimum separation distances that would reduce the risks to nearby nuclear facilities. The resulting minimum separation distances are shown in Table ES.1.« less

Saddle point localization of molecular wavefunctions.

PubMed

Mellau, Georg Ch; Kyuberis, Alexandra A; Polyansky, Oleg L; Zobov, Nikolai; Field, Robert W

2016-09-15

The quantum mechanical description of isomerization is based on bound eigenstates of the molecular potential energy surface. For the near-minimum regions there is a textbook-based relationship between the potential and eigenenergies. Here we show how the saddle point region that connects the two minima is encoded in the eigenstates of the model quartic potential and in the energy levels of the [H, C, N] potential energy surface. We model the spacing of the eigenenergies with the energy dependent classical oscillation frequency decreasing to zero at the saddle point. The eigenstates with the smallest spacing are localized at the saddle point. The analysis of the HCN ↔ HNC isomerization states shows that the eigenstates with small energy spacing relative to the effective (v1, v3, ℓ) bending potentials are highly localized in the bending coordinate at the transition state. These spectroscopically detectable states represent a chemical marker of the transition state in the eigenenergy spectrum. The method developed here provides a basis for modeling characteristic patterns in the eigenenergy spectrum of bound states.

Mixed quantum-classical studies of energy partitioning in unimolecular chemical reactions

NASA Astrophysics Data System (ADS)

Bladow, Landon Lowell

A mixed quantum-classical reaction path Hamiltonian method is utilized to study the dynamics of unimolecular reactions. The method treats motion along the reaction path classically and treats the transverse vibrations quantum mechanically. The theory leads to equations that predict the disposai of the exit-channel potential energy to product translation and vibration. In addition, vibrational state distributions are obtained for the product normal modes. Vibrational excitation results from the curvature of the minimum energy reaction path. The method is applied to six unimolecular reactions: HF elimination from fluoroethane, 1,1-difluoroethane, 1,1-difluoroethene, and trifluoromethane; and HCl elimination from chloroethane and acetyl chloride. The minimum energy paths were calculated at either the MP2 or B3LYP level of theory. In all cases, the majority of the vibrational excitation of the products occurs in the HX fragment. The results are compared to experimental data and other theoretical results, where available. The best agreement between the experimental and calculated HX vibrational distributions is found for the halogenated ethanes, and the experimental deduction that the majority of the HX vibrational excitation arises from the potential energy release is supported. It is believed that the excess energy provided in experiments contributes to the poorer agreement between experiment and theory observed for HF elimination from 1,1-difluoroethene and trifluoromethane. An attempt is described to incorporate a treatment of the excess energy into the present method. However, the sign of the curvature coupling elements is then found to affect the dynamics. Overall, the method appears to be an efficient dynamical tool for modeling the disposal of the exit-channel potential energy in unimolecular reactions.

On bound-states of the Gross Neveu model with massive fundamental fermions

NASA Astrophysics Data System (ADS)

Frishman, Yitzhak; Sonnenschein, Jacob

2018-01-01

In the search for QFT's that admit boundstates, we reinvestigate the two dimensional Gross-Neveu model, but with massive fermions. By computing the self-energy for the auxiliary boundstate field and the effective potential, we show that there are no bound states around the lowest minimum, but there is a meta-stable bound state around the other minimum, a local one. The latter decays by tunneling. We determine the dependence of its lifetime on the fermion mass and coupling constant.

Life cycle optimization model for integrated cogeneration and energy systems applications in buildings

NASA Astrophysics Data System (ADS)

Osman, Ayat E.

Energy use in commercial buildings constitutes a major proportion of the energy consumption and anthropogenic emissions in the USA. Cogeneration systems offer an opportunity to meet a building's electrical and thermal demands from a single energy source. To answer the question of what is the most beneficial and cost effective energy source(s) that can be used to meet the energy demands of the building, optimizations techniques have been implemented in some studies to find the optimum energy system based on reducing cost and maximizing revenues. Due to the significant environmental impacts that can result from meeting the energy demands in buildings, building design should incorporate environmental criteria in the decision making criteria. The objective of this research is to develop a framework and model to optimize a building's operation by integrating congregation systems and utility systems in order to meet the electrical, heating, and cooling demand by considering the potential life cycle environmental impact that might result from meeting those demands as well as the economical implications. Two LCA Optimization models have been developed within a framework that uses hourly building energy data, life cycle assessment (LCA), and mixed-integer linear programming (MILP). The objective functions that are used in the formulation of the problems include: (1) Minimizing life cycle primary energy consumption, (2) Minimizing global warming potential, (3) Minimizing tropospheric ozone precursor potential, (4) Minimizing acidification potential, (5) Minimizing NOx, SO 2 and CO2, and (6) Minimizing life cycle costs, considering a study period of ten years and the lifetime of equipment. The two LCA optimization models can be used for: (a) long term planning and operational analysis in buildings by analyzing the hourly energy use of a building during a day and (b) design and quick analysis of building operation based on periodic analysis of energy use of a building in a year. A Pareto-optimal frontier is also derived, which defines the minimum cost required to achieve any level of environmental emission or primary energy usage value or inversely the minimum environmental indicator and primary energy usage value that can be achieved and the cost required to achieve that value.

Chemistry of Aviation Fuels

NASA Technical Reports Server (NTRS)

Knepper, Bryan; Hwang, Soon Muk; DeWitt, Kenneth J.

2004-01-01

Minimum ignition energies of various methanol/air mixtures were measured in a temperature controlled constant volume combustion vessel using a spark ignition method with a spark gap distance of 2 mm. The minimum ignition energies decrease rapidly as the mixture composition (equivalence ratio, Phi) changes from lean to stoichiometric, reach a minimum value, and then increase rather slowly with Phi. The minimum of the minimum ignition energy (MIE) and the corresponding mixture composition were determined to be 0.137 mJ and Phi = 1.16, a slightly rich mixture. The variation of minimum ignition energy with respect to the mixture composition is explained in terms of changes in reaction chemistry.

Minimum energy control and optimal-satisfactory control of Boolean control network

NASA Astrophysics Data System (ADS)

Li, Fangfei; Lu, Xiwen

2013-12-01

In the literatures, to transfer the Boolean control network from the initial state to the desired state, the expenditure of energy has been rarely considered. Motivated by this, this Letter investigates the minimum energy control and optimal-satisfactory control of Boolean control network. Based on the semi-tensor product of matrices and Floyd's algorithm, minimum energy, constrained minimum energy and optimal-satisfactory control design for Boolean control network are given respectively. A numerical example is presented to illustrate the efficiency of the obtained results.

Plasma Relaxation and Topological Aspects in Electron Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, Bhimsen

2016-10-01

Parker's formulation of isotopological plasma relaxation process toward minimum magnetics energy states in magnetohydrodynamics (MHD) is extended to electron MHD (EMHD). The lower bound on magnetic energy in EMHD is determined by both the magnetic field and the electron vorticity field topologies, and is shown to be reduced further in EMHD by an amount proportional to the sum of total electron-flow kinetic energy and total electron-flow enstrophy. The EMHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics, and the torsion coefficient and turns out to be proportional to potential vorticity. The winding pattern of the magnetic field lines appears to evolve therefore in the same way as potential vorticity lines in 2D hydrodynamics.

Plasma relaxation and topological aspects in electron magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Shivamoggi, B. K.

2016-07-01

Parker's formulation of isotopological plasma relaxation process toward minimum magnetics energy states in magnetohydrodynamics (MHD) is extended to electron MHD (EMHD). The lower bound on magnetic energy in EMHD is determined by both the magnetic field and the electron vorticity field topologies, and is shown to be reduced further in EMHD by an amount proportional to the sum of total electron-flow kinetic energy and total electron-flow enstrophy. The EMHD Beltrami condition becomes equivalent to the potential vorticity conservation equation in two-dimensional (2D) hydrodynamics, and the torsion coefficient α turns out to be proportional to potential vorticity. The winding pattern of the magnetic field lines appears to evolve, therefore, in the same way as potential vorticity lines in 2D hydrodynamics.

10 CFR 862.6 - Voluntary minimum altitude.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 4 2011-01-01 2011-01-01 false Voluntary minimum altitude. 862.6 Section 862.6 Energy DEPARTMENT OF ENERGY RESTRICTIONS ON AIRCRAFT LANDING AND AIR DELIVERY AT DEPARTMENT OF ENERGY NUCLEAR SITES... designated site. Applicable FAA prohibitions or restrictions take precedence over this voluntary minimum...

Photoionization of NaK molecule with a double-well potential in femtosecond pump probe pulse laser fields

NASA Astrophysics Data System (ADS)

Yu, Jie; Wang, Sen-Ming; Yuan, Kai-Jun; Cong, Shu-Lin

2006-09-01

The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 61Σ+ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 61Σ+ state can be extracted from the photoelectron energy spectra.

REopt Screenings Catalyze Development of Hundreds of Megawatts of Renewable Energy for Federal Agencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Federal Energy Management Program (FEMP) offers renewable energy project assistance to federal agencies, which often begins with a desktop screening to develop a prioritized portfolio of project opportunities. FEMP uses the National Renewable Energy Laboratory's REopt energy planning platform to screen potential renewable energy opportunities at a single site or across a range of sites. REopt helps organizations prioritize the most economi­cally and technically viable projects for further study and identifies the size and mix of technologies that meet the orga­nization's goals at minimum cost, along with the optimal operating strategies.

10 CFR 862.6 - Voluntary minimum altitude.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Voluntary minimum altitude. 862.6 Section 862.6 Energy DEPARTMENT OF ENERGY RESTRICTIONS ON AIRCRAFT LANDING AND AIR DELIVERY AT DEPARTMENT OF ENERGY NUCLEAR SITES § 862.6 Voluntary minimum altitude. In addition to complying with all applicable FAA prohibitions or...

Accumulator for Low-Energy Laser-Cooled Particles

NASA Astrophysics Data System (ADS)

Mertes, Kevin; Walstrom, Peter; di Rosa, Michael; LANL Collaboration

2017-04-01

An accumulator builds phase-space density by use of a non-Hamiltonian process, thereby circumventing Liouville's theorem, which states that phase-space density is preserved in processes governed by Hamilton's equations. We have built an accumulator by a simple magneto-static cusp trap formed from two ring shaped permanent magnets. In traps with a central minimum of | B | , the stored particles are in a field-repelled (FR) Zeeman state, pushed away by | B | and oscillating about its minimum. After laser-cooling our particles and before entering the trap, we employ the non-hamiltonian process of optical pumping: A FR particle approaches the trap and climbs to the top of the confining potential with a finite velocity. There, it is switched to a field seeking (FS) state. As the switch does not change the velocity, the particle proceeds into the trap but continues to lose momentum because, now in the FS state, the particles sees the decreasing field as a potential hill to climb. Before it comes to a halt, the particle is switched back to a FR state for storage. The process repeats, building the trapped number and density. A simple consideration of potential and kinetic energies would show the trapped particles to have less kinetic energy than those injected. Los Alamos National Laboratory's Office of Laboratory Directed Research and Development.

Energy and IAQ Implications of Alternative Minimum Ventilation Rates in California Retail and School Buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutton, Spencer M.; Fisk, William J.

For a stand-alone retail building, a primary school, and a secondary school in each of the 16 California climate zones, the EnergyPlus building energy simulation model was used to estimate how minimum mechanical ventilation rates (VRs) affect energy use and indoor air concentrations of an indoor-generated contaminant. The modeling indicates large changes in heating energy use, but only moderate changes in total building energy use, as minimum VRs in the retail building are changed. For example, predicted state-wide heating energy consumption in the retail building decreases by more than 50% and total building energy consumption decreases by approximately 10% asmore » the minimum VR decreases from the Title 24 requirement to no mechanical ventilation. The primary and secondary schools have notably higher internal heat gains than in the retail building models, resulting in significantly reduced demand for heating. The school heating energy use was correspondingly less sensitive to changes in the minimum VR. The modeling indicates that minimum VRs influence HVAC energy and total energy use in schools by only a few percent. For both the retail building and the school buildings, minimum VRs substantially affected the predicted annual-average indoor concentrations of an indoor generated contaminant, with larger effects in schools. The shape of the curves relating contaminant concentrations with VRs illustrate the importance of avoiding particularly low VRs.« less

A new method for finding the minimum free energy pathway of ions and small molecule transportation through protein based on 3D-RISM theory and the string method

NASA Astrophysics Data System (ADS)

Yoshida, Norio

2018-05-01

A new method for finding the minimum free energy pathway (MFEP) of ions and small molecule transportation through a protein based on the three-dimensional reference interaction site model (3D-RISM) theory combined with the string method has been proposed. The 3D-RISM theory produces the distribution function, or the potential of mean force (PMF), for transporting substances around the given protein structures. By applying the string method to the PMF surface, one can readily determine the MFEP on the PMF surface. The method has been applied to consider the Na+ conduction pathway of channelrhodopsin as an example.

On a Minimum Problem in Smectic Elastomers

NASA Astrophysics Data System (ADS)

Buonsanti, Michele; Giovine, Pasquale

2008-07-01

Smectic elastomers are layered materials exhibiting a solid-like elastic response along the layer normal and a rubbery one in the plane. Balance equations for smectic elastomers are derived from the general theory of continua with constrained microstructure. In this work we investigate a very simple minimum problem based on multi-well potentials where the microstructure is taken into account. The set of polymeric strains minimizing the elastic energy contains a one-parameter family of simple strain associated with a micro-variation of the degree of freedom. We develop the energy functional through two terms, the first one nematic and the second one considering the tilting phenomenon; after, by developing in the rubber elasticity framework, we minimize over the tilt rotation angle and extract the engineering stress.

Conformational Analysis of Stiff Chiral Polymers with End-Constraints

PubMed Central

Kim, Jin Seob; Chirikjian, Gregory S.

2010-01-01

We present a Lie-group-theoretic method for the kinematic and dynamic analysis of chiral semi-flexible polymers with end constraints. The first is to determine the minimum energy conformations of semi-flexible polymers with end constraints, and the second is to perform normal mode analysis based on the determined minimum energy conformations. In this paper, we use concepts from the theory of Lie groups and principles of variational calculus to model such polymers as inextensible or extensible chiral elastic rods with coupling between twisting and bending stiffnesses, and/or between twisting and extension stiffnesses. This method is general enough to include any stiffness and chirality parameters in the context of elastic filament models with the quadratic elastic potential energy function. As an application of this formulation, the analysis of DNA conformations is discussed. We demonstrate our method with examples of DNA conformations in which topological properties such as writhe, twist, and linking number are calculated from the results of the proposed method. Given these minimum energy conformations, we describe how to perform the normal mode analysis. The results presented here build both on recent experimental work in which DNA mechanical properties have been measured, and theoretical work in which the mechanics of non-chiral elastic rods has been studied. PMID:20198114

Action Potential Energy Efficiency Varies Among Neuron Types in Vertebrates and Invertebrates

PubMed Central

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B.; Niven, Jeremy E.

2010-01-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na+ and K+ currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin–Huxley model of the squid axon, optimizing the kinetics or number of Na+ and K+ channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost. PMID:20617202

Action potential energy efficiency varies among neuron types in vertebrates and invertebrates.

PubMed

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B; Niven, Jeremy E

2010-07-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na(+) and K(+) currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin-Huxley model of the squid axon, optimizing the kinetics or number of Na(+) and K(+) channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost.

Motion of a Janus particle very near a wall

NASA Astrophysics Data System (ADS)

Rashidi, Aidin; Wirth, Christopher L.

2017-12-01

This article describes the simulated Brownian motion of a sphere comprising hemispheres of unequal zeta potential (i.e., "Janus" particle) very near a wall. The simulation tool was developed and used to assist in the methodology development for applying Total Internal Reflection Microscopy (TIRM) to anisotropic particles. Simulations of the trajectory of a Janus sphere with cap density matching that of the base particle very near a boundary were used to construct 3D potential energy landscapes that were subsequently used to infer particle and solution properties, as would be done in a TIRM measurement. Results showed that the potential energy landscape of a Janus sphere has a transition region at the location of the boundary between the two Janus halves, which depended on the relative zeta potential magnitude. The potential energy landscape was fit to accurately obtain the zeta potential of each hemisphere, particle size, minimum potential energy position and electrolyte concentration, or Debye length. We also determined the appropriate orientation bin size and regimes over which the potential energy landscape should be fit to obtain system properties. Our simulations showed that an experiment may require more than 106 observations to obtain a suitable potential energy landscape as a consequence of the multivariable nature of observations for an anisotropic particle. These results illustrate important considerations for conducting TIRM for anisotropic particles.

Numerical solution of open string field theory in Schnabl gauge

NASA Astrophysics Data System (ADS)

Arroyo, E. Aldo; Fernandes-Silva, A.; Szitas, R.

2018-01-01

Using traditional Virasoro L 0 level-truncation computations, we evaluate the open bosonic string field theory action up to level (10 , 30). Extremizing this level-truncated potential, we construct a numerical solution for tachyon condensation in Schnabl gauge. We find that the energy associated to the numerical solution overshoots the expected value -1 at level L = 6. Extrapolating the level-truncation data for L ≤ 10 to estimate the vacuum energies for L > 10, we predict that the energy reaches a minimum value at L ˜ 12, and then turns back to approach -1 asymptotically as L → ∞. Furthermore, we analyze the tachyon vacuum expectation value (vev), for which by extrapolating its corresponding level-truncation data, we predict that the tachyon vev reaches a minimum value at L ˜ 26, and then turns back to approach the expected analytical result as L → ∞.

MEAN MINIMUM TEMPERATURE DATA - U.S HISTORICAL CLIMATOLOGY NETWORK (HCN)

EPA Science Inventory

The Carbon Dioxide Information Analysis Center, which includes the World Data Center-A for Atmospheric Trace Gases, is the primary global-change data and information analysis center of the U.S. Department of Energy (DOE). CDIACs scope includes potentially anything and everything...

Reactive Resonances in N+N2 Exchange Reaction

NASA Technical Reports Server (NTRS)

Wang, Dunyou; Huo, Winifred M.; Dateo, Christopher E.; Schwenke, David W.; Stallcop, James R.

2003-01-01

Rich reactive resonances are found in a 3D quantum dynamics study of the N + N2 exchange reaction using a recently developed ab initio potential energy surface. This surface is characterized by a feature in the interaction region called Lake Eyring , that is, two symmetric transition states with a shallow minimum between them. An L2 analysis of the quasibound states associated with the shallow minimum confirms that the quasibound states associated with oscillations in all three degrees of freedom in Lake Eyring are responsible for the reactive resonances in the state-to-state reaction probabilities. The quasibound states, mostly the bending motions, give rise to strong reasonance peaks, whereas other motions contribute to the bumps and shoulders in the resonance structure. The initial state reaction probability further proves that the bending motions are the dominating factors of the reaction probability and have longer life times than the stretching motions. This is the first observation of reactive resonances from a "Lake Eyring" feature in a potential energy surface.

Building Efficiency Evaluation and Uncertainty Analysis with DOE's Asset Score Preview

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2016-08-12

Building Energy Asset Score Tool, developed by the U.S. Department of Energy (DOE), is a program to encourage energy efficiency improvement by helping building owners and managers assess a building's energy-related systems independent of operations and maintenance. Asset Score Tool uses a simplified EnergyPlus model to provide an assessment of building systems, through minimum user inputs of basic building characteristics. Asset Score Preview is a newly developed option that allows users to assess their building's systems and the potential value of a more in-depth analysis via an even more simplified approach. This methodology provides a preliminary approach to estimating amore » building's energy efficiency and potential for improvement. This paper provides an overview of the methodology used for the development of Asset Score Preview and the scoring methodology.« less

Development of an Empirical Model for Optimization of Machining Parameters to Minimize Power Consumption

NASA Astrophysics Data System (ADS)

Kant Garg, Girish; Garg, Suman; Sangwan, K. S.

2018-04-01

The manufacturing sector consumes huge energy demand and the machine tools used in this sector have very less energy efficiency. Selection of the optimum machining parameters for machine tools is significant for energy saving and for reduction of environmental emission. In this work an empirical model is developed to minimize the power consumption using response surface methodology. The experiments are performed on a lathe machine tool during the turning of AISI 6061 Aluminum with coated tungsten inserts. The relationship between the power consumption and machining parameters is adequately modeled. This model is used for formulation of minimum power consumption criterion as a function of optimal machining parameters using desirability function approach. The influence of machining parameters on the energy consumption has been found using the analysis of variance. The validation of the developed empirical model is proved using the confirmation experiments. The results indicate that the developed model is effective and has potential to be adopted by the industry for minimum power consumption of machine tools.

Computed Potential Energy Surfaces and Minimum Energy Pathways for Chemical Reactions

NASA Technical Reports Server (NTRS)

Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

1994-01-01

Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. For some dynamics methods, global potential energy surfaces are required. In this case, it is necessary to obtain the energy at a complete sampling of all the possible arrangements of the nuclei, which are energetically accessible, and then a fitting function must be obtained to interpolate between the computed points. In other cases, characterization of the stationary points and the reaction pathway connecting them is sufficient. These properties may be readily obtained using analytical derivative methods. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives usefull results for a number of chemically important systems. The talk will focus on a number of applications including global potential energy surfaces, H + O2, H + N2, O(3p) + H2, and reaction pathways for complex reactions, including reactions leading to NO and soot formation in hydrocarbon combustion.

Consistent force field modeling of matrix isolated molecules. V. Minimum energy path potential to the conformer conversion of 1,2-difluoroethane: Ar 364, ab initio calculation of electric multipole moments and electric polarization contribution to the conversion barrier

NASA Astrophysics Data System (ADS)

Gunde, R.; Ha, T.-K.; Günthard, H. H.

1990-08-01

In this paper results of consistent force field modeling (CFF) of the potential function to conversion of the gauche (g) to the trans (t) conformer of 1,2-difluoroethane (DFE) isolated in an argon matrix will be reported. Starting point are locally stable configurations gDFE:Ar 364 (defect GH1) and tDFE:Ar 364 (TH1) obtained in previous work from CFF modeling of a cube shaped Ar 364 fragment containing one DFE molecule in its center. Using the dihedral angle of DFE as an independent parameter the minimum energy path of the conversion process gDFE:Ar 364→tDFE:Ar 364 will be determined by CFF energy minimization. Determination of the minimum energy path is found to require large numbers of energy minimization steps and to lead to a rather complicated motion of the molecule with respect to the crystal fragment. Surprisingly the molecule-matrix interactions lead to a reduction of the g-t barrier by ≈500 cal/mol and to a stabilization of the trans species by ≈500 cal/mol. This finding is a consequence of a delicate interplay of matrix-molecule and matrix-matrix interactions. Calculation of the electric polarization energy (induced dipole-first-order polarization approximation) is based on extended ab initio calculations of dipole and quadrupole moments and a bond polarizability estimate of the first-order polarizability of DFE as a function of the internal rotation angle, on Fourier expansion of multipole components and use of symmetry for reduction of the order of the linear system defining the (self-consistent) induced dipole moments of all Ar atoms. Electric polarization is found to alter the potential function of the conversion process in a profound way: the g-t barrier and the t-g energy difference are increased to ≈3000 cal/mol and to ≈1500 cal/mol respectively (≈2500 and ≈530 cal/mol respectively for free DFE). Further applications of the technique developed in this work to related problems of matrix isolated molecules, e.g., vibrational matrix shifts will be discussed.

Energy Requirements of Hydrogen-utilizing Microbes: A Boundary Condition for Subsurface Life

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S.

2003-01-01

Microbial ecosystems based on the energy supplied by water-rock chemistry carry particular significance in the context of geo- and astrobiology. With no direct dependence on solar energy, lithotrophic microbes could conceivably penetrate a planetary crust to a depth limited only by temperature or pressure constraints (several kilometers or more). The deep lithospheric habitat is thereby potentially much greater in volume than its surface counterpart, and in addition offers a stable refuge against inhospitable surface conditions related to climatic or atmospheric evolution (e.g., Mars) or even high-energy impacts (e.g., early in Earth's history). The possibilities for a deep microbial biosphere are, however, greatly constrained by life s need to obtain energy at a certain minimum rate (the maintenance energy requirement) and of a certain minimum magnitude (the energy quantum requirement). The mere existence of these requirements implies that a significant fraction of the chemical free energy available in the subsurface environment cannot be exploited by life. Similar limits may also apply to the usefulness of light energy at very low intensities or long wavelengths. Quantification of these minimum energy requirements in terrestrial microbial ecosystems will help to establish a criterion of energetic habitability that can significantly constrain the prospects for life in Earth's subsurface, or on other bodies in the solar system. Our early work has focused on quantifying the biological energy quantum requirement for methanogenic archaea, as representatives of a plausible subsurface metabolism, in anoxic sediments (where energy availability is among the most limiting factors in microbial population growth). In both field and laboratory experiments utilizing these sediments, methanogens retain a remarkably consistent free energy intake, in the face of fluctuating environmental conditions that affect energy availability. The energy yields apparently required by methanogens in these sediment systems for sustained metabolism are about half that previously thought necessary. Lowered energy requirements would imply that a correspondingly greater proportion of the planetary subsurface could represent viable habitat for microorganisms.

MEPSA: minimum energy pathway analysis for energy landscapes.

PubMed

Marcos-Alcalde, Iñigo; Setoain, Javier; Mendieta-Moreno, Jesús I; Mendieta, Jesús; Gómez-Puertas, Paulino

2015-12-01

From conformational studies to atomistic descriptions of enzymatic reactions, potential and free energy landscapes can be used to describe biomolecular systems in detail. However, extracting the relevant data of complex 3D energy surfaces can sometimes be laborious. In this article, we present MEPSA (Minimum Energy Path Surface Analysis), a cross-platform user friendly tool for the analysis of energy landscapes from a transition state theory perspective. Some of its most relevant features are: identification of all the barriers and minima of the landscape at once, description of maxima edge profiles, detection of the lowest energy path connecting two minima and generation of transition state theory diagrams along these paths. In addition to a built-in plotting system, MEPSA can save most of the generated data into easily parseable text files, allowing more versatile uses of MEPSA's output such as the generation of molecular dynamics restraints from a calculated path. MEPSA is freely available (under GPLv3 license) at: http://bioweb.cbm.uam.es/software/MEPSA/ CONTACT: pagomez@cbm.csic.es. Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

A Method for Modeling Household Occupant Behavior to Simulate Residential Energy Consumption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Brandon J; Starke, Michael R; Abdelaziz, Omar

2014-01-01

This paper presents a statistical method for modeling the behavior of household occupants to estimate residential energy consumption. Using data gathered by the U.S. Census Bureau in the American Time Use Survey (ATUS), actions carried out by survey respondents are categorized into ten distinct activities. These activities are defined to correspond to the major energy consuming loads commonly found within the residential sector. Next, time varying minute resolution Markov chain based statistical models of different occupant types are developed. Using these behavioral models, individual occupants are simulated to show how an occupant interacts with the major residential energy consuming loadsmore » throughout the day. From these simulations, the minimum number of occupants, and consequently the minimum number of multiple occupant households, needing to be simulated to produce a statistically accurate representation of aggregate residential behavior can be determined. Finally, future work will involve the use of these occupant models along side residential load models to produce a high-resolution energy consumption profile and estimate the potential for demand response from residential loads.« less

Theoretical Study of Tautomerization Reactions for the Ground and First Excited Electronic States of Adenine

NASA Technical Reports Server (NTRS)

Salter, Latasha M.; Chaban, Galina M.; Kwak, Dochan (Technical Monitor)

2002-01-01

Geometrical structures and energetic properties for different tautomers of adenine are calculated in this study, using multi-configurational wave functions. Both the ground and the lowest singlet excited state potential energy surfaces are studied. Four tautomeric forms are considered, and their energetic order is found to be different on the ground and the excited state potential energy surfaces. Minimum energy reaction paths are obtained for hydrogen atom transfer (tautomerization) reactions in the ground and the lowest excited electronic states. It is found that the barrier heights and the shapes of the reaction paths are different for the ground and the excited electronic states, suggesting that the probability of such tautomerization reaction is higher on the excited state potential energy surface. This tautomerization process should become possible in the presence of water or other polar solvent molecules and should play an important role in the photochemistry of adenine.

Experimental Potential Energy Curve for the 43 Π Electronic State of NaCs

NASA Astrophysics Data System (ADS)

Steely, Andrew; Cooper, Hannah; Zain, Hareem; Whipp, Ciara; Faust, Carl; Kortyna, Andrew; Huennekens, John

2017-04-01

We present results from experimental studies of the 43 Π electronic state of the NaCs molecule. This electronic state is interesting in that its potential energy curve likely exhibits a double minimum. As a result, interference effects are observed in the resolved bound-free fluorescence spectra. The optical-optical double resonance method was used to obtain Doppler-free excitation spectra for the 43 Π state. This dataset of measured level energies was expanded largely by observing fluorescence from levels populated by collisions. To aid in level assignments, simulations of resolved bound-free fluorescence spectra were calculated using the BCONT program (R. J. Le Roy, University of Waterloo). Spectroscopic constants were determined to summarize data belonging to inner well, outer well, and above barrier regions of the electronic state. Current work focuses on using the IPA method to construct an experimental potential energy curve. Work supported by NSF and Susquehanna University.

Dark energy from the motions of neutrinos

NASA Astrophysics Data System (ADS)

Simpson, Fergus; Jimenez, Raul; Pena-Garay, Carlos; Verde, Licia

2018-06-01

Ordinarily, a scalar field may only play the role of dark energy if it possesses a potential that is either extraordinarily flat or extremely fine-tuned. Here we demonstrate that these restrictions are lifted when the scalar field undergoes persistent energy exchange with another fluid. In this scenario, the field is prevented from reversing its direction of motion, and instead may come to rest while displaced from the local minimum of its potential. Therefore almost any scalar potential is capable of initiating a prolonged phase of cosmic acceleration. If the rate of energy transfer is modulated via a derivative coupling, the field undergoes a rapid process of freezing, after which the field's equation of state mimicks that of a cosmological constant. We present a physically motivated realisation in the form of a neutrino-majoron coupling, which avoids the dynamical instabilities associated with mass-varying neutrino models. Finally we discuss possible means by which this model could be experimentally verified.

Parametrization of Stillinger-Weber potential based on valence force field model: application to single-layer MoS2 and black phosphorus

NASA Astrophysics Data System (ADS)

Jiang, Jin-Wu

2015-08-01

We propose parametrizing the Stillinger-Weber potential for covalent materials starting from the valence force-field model. All geometrical parameters in the Stillinger-Weber potential are determined analytically according to the equilibrium condition for each individual potential term, while the energy parameters are derived from the valence force-field model. This parametrization approach transfers the accuracy of the valence force field model to the Stillinger-Weber potential. Furthermore, the resulting Stilliinger-Weber potential supports stable molecular dynamics simulations, as each potential term is at an energy-minimum state separately at the equilibrium configuration. We employ this procedure to parametrize Stillinger-Weber potentials for single-layer MoS2 and black phosphorous. The obtained Stillinger-Weber potentials predict an accurate phonon spectrum and mechanical behaviors. We also provide input scripts of these Stillinger-Weber potentials used by publicly available simulation packages including GULP and LAMMPS.

Parametrization of Stillinger-Weber potential based on valence force field model: application to single-layer MoS2 and black phosphorus.

PubMed

Jiang, Jin-Wu

2015-08-07

We propose parametrizing the Stillinger-Weber potential for covalent materials starting from the valence force-field model. All geometrical parameters in the Stillinger-Weber potential are determined analytically according to the equilibrium condition for each individual potential term, while the energy parameters are derived from the valence force-field model. This parametrization approach transfers the accuracy of the valence force field model to the Stillinger-Weber potential. Furthermore, the resulting Stilliinger-Weber potential supports stable molecular dynamics simulations, as each potential term is at an energy-minimum state separately at the equilibrium configuration. We employ this procedure to parametrize Stillinger-Weber potentials for single-layer MoS2 and black phosphorous. The obtained Stillinger-Weber potentials predict an accurate phonon spectrum and mechanical behaviors. We also provide input scripts of these Stillinger-Weber potentials used by publicly available simulation packages including GULP and LAMMPS.

Potential of mean force between two hydrophobic solutes in water.

PubMed

Southall, Noel T; Dill, Ken A

2002-12-10

We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory. Copyright 2002 Elsevier Science B.V.

On-the-Fly Machine Learning of Atomic Potential in Density Functional Theory Structure Optimization

NASA Astrophysics Data System (ADS)

Jacobsen, T. L.; Jørgensen, M. S.; Hammer, B.

2018-01-01

Machine learning (ML) is used to derive local stability information for density functional theory calculations of systems in relation to the recently discovered SnO2 (110 )-(4 ×1 ) reconstruction. The ML model is trained on (structure, total energy) relations collected during global minimum energy search runs with an evolutionary algorithm (EA). While being built, the ML model is used to guide the EA, thereby speeding up the overall rate by which the EA succeeds. Inspection of the local atomic potentials emerging from the model further shows chemically intuitive patterns.

Steady state compact toroidal plasma production

DOEpatents

Turner, William C.

1986-01-01

Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.

Evaluating the Sonic Layer Depth Relative to the Mixed Layer Depth

DTIC Science & Technology

2008-07-24

upper ocean to trap acoustic energy in a surface duct while MLD characterizes upper ocean mixing. The SLD is computed from temperature and salinity...and compared over the annual cycle. The SLD characterizes the potential of the upper ocean to trap acoustic energy in a surface duct while MLD...exists a tropical cyclone formation [e.g., Mao et al., 2000], to Minimum acoustic Cutoff Frequency (MCF) above which phytoplankton bloom critical depth

Research and Development Services: Methods Development

DTIC Science & Technology

1982-07-23

At an applied potential of -1.15 volts, the minimum detectable amount was 500 ng, which was not very sensitive. From Hammett linear free energy... Equation 1, the value of N was optimized by using two columns. The other factors which can influence resolution are the capacity factor, k, and the

Observation of b 2 symmetry vibrational levels of the SO 2C 1B 2 state: Vibrational level staggering, Coriolis interactions, and rotation-vibration constants

DOE PAGES

Park, G. Barratt; Jiang, Jun; Saladrigas, Catherine A.; ...

2016-04-14

Here, the C 1B 2 state of SO 2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. However, low-lying levels with odd quanta of antisymmetric stretch (b 2 vibrational symmetry) have not previously been observed because transitions into these levels from the zero-point level of the X ~ state are vibronically forbidden. We use IR-UV double resonance to observe the b 2 vibrational levels of the C state below 1600 cm –1 of vibrational excitation. This enables a direct characterization of the vibrational level staggering that results frommore » the double-minimum potential. In addition, it allows us to deperturb the strong c-axis Coriolis interactions between levels of a 1 and b 2 vibrational symmetry, and to determine accurately the vibrational dependence of the rotational constants in the distorted C electronic state.« less

Observation of b 2 symmetry vibrational levels of the SO 2C 1B 2 state: Vibrational level staggering, Coriolis interactions, and rotation-vibration constants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, G. Barratt; Jiang, Jun; Saladrigas, Catherine A.

Here, the C 1B 2 state of SO 2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. However, low-lying levels with odd quanta of antisymmetric stretch (b 2 vibrational symmetry) have not previously been observed because transitions into these levels from the zero-point level of the X ~ state are vibronically forbidden. We use IR-UV double resonance to observe the b 2 vibrational levels of the C state below 1600 cm –1 of vibrational excitation. This enables a direct characterization of the vibrational level staggering that results frommore » the double-minimum potential. In addition, it allows us to deperturb the strong c-axis Coriolis interactions between levels of a 1 and b 2 vibrational symmetry, and to determine accurately the vibrational dependence of the rotational constants in the distorted C electronic state.« less

Potential energy surface and vibrational band origins of the triatomic lithium cation

NASA Astrophysics Data System (ADS)

Searles, Debra J.; Dunne, Simon J.; von Nagy-Felsobuki, Ellak I.

The 104 point CISD Li +3 potential energy surface and its analytical representation is reported. The calculations predict the minimum energy geometry to be an equilateral triangle of side RLiLi = 3.0 Å and of energy - 22.20506 E h. A fifth-order Morse—Dunham type analytical force field is used in the Carney—Porter normal co-ordinate vibrational Hamiltonian, the corresponding eigenvalue problem being solved variationally using a 560 configurational finite-element basis set. The predicted assignment of the vibrational band origins is in accord with that reported for H +3. Moreover, for 6Li +3 and 7Li +3 the lowest i.r. accessible band origin is the overlineν0,1,±1 predicted to be at 243.6 and 226.0 cm -1 respectively.

Assessment of Energy Savings Potential from the Use of Demand Control Ventilation Systems in General Office Spaces in California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Tianzhen; Fisk, William J.

2009-07-08

Demand controlled ventilation (DCV) was evaluated for general office spaces in California. A medium size office building meeting the prescriptive requirements of the 2008 California building energy efficiency standards (CEC 2008) was assumed in the building energy simulations performed with the EnergyPlus program to calculate the DCV energy savings potential in five typical California climates. Three design occupancy densities and two minimum ventilation rates were used as model inputs to cover a broader range of design variations. The assumed values of minimum ventilation rates in offices without DCV, based on two different measurement methods, were 81 and 28 cfm per occupant. These rates are based on the co-author's unpublished analyses of data from EPA's survey of 100 U.S. office buildings. These minimum ventilation rates exceed the 15 to 20 cfm per person required in most ventilation standards for offices. The cost effectiveness of applying DCV in general office spaces was estimated via a life cycle cost analyses that considered system costs and energy cost reductions. The results of the energy modeling indicate that the energy savings potential of DCV is largest in the desert area of California (climate zone 14), followed by Mountains (climate zone 16), Central Valley (climate zone 12), North Coast (climate zone 3), and South Coast (climate zone 6). The results of the life cycle cost analysis show DCV is cost effective for office spaces if the typical minimum ventilation rates without DCV is 81 cfm per person, except at the low design occupancy of 10 people per 1000 ft{sup 2} in climate zones 3 and 6. At the low design occupancy of 10 people per 1000 ft{sup 2}, the greatest DCV life cycle cost savings is a net present value (NPV) ofmore » $$0.52/ft{sup 2} in climate zone 14, followed by $$0.32/ft{sup 2} in climate zone 16 and $$0.19/ft{sup 2} in climate zone 12. At the medium design occupancy of 15 people per 1000 ft{sup 2}, the DCV savings are higher with a NPV $$0.93/ft{sup 2} in climate zone 14, followed by $$0.55/ft{sup 2} in climate zone 16, $$0.46/ft{sup 2} in climate zone 12, $$0.30/ft{sup 2} in climate zone 3, $$0.16/ft{sup 2} in climate zone 3. At the high design occupancy of 20 people per 1000 ft{sup 2}, the DCV savings are even higher with a NPV $$1.37/ft{sup 2} in climate zone 14, followed by $$0.86/ft{sup 2} in climate zone 16, $$0.84/ft{sup 2} in climate zone 3, $$0.82/ft{sup 2} in climate zone 12, and $0.65/ft{sup 2} in climate zone 6. DCV was not found to be cost effective if the typical minimum ventilation rate without DCV is 28 cfm per occupant, except at high design occupancy of 20 people per 1000 ft{sup 2} in climate zones 14 and 16. Until the large uncertainties about the base case ventilation rates in offices without DCV are reduced, the case for requiring DCV in general office spaces will be a weak case.« less

The structure of the NO(X (2)Pi)-N(2) complex: A joint experimental-theoretical study.

PubMed

Wen, B; Meyer, H; Kłos, J

2010-04-21

We report the first measurement of the spectrum of the NO-N(2) complex in the region of the first vibrational NO overtone transition. The origin band of the complex is blueshifted by 0.30 cm(-1) from the corresponding NO monomer frequency. The observed spectrum consists of three bands assigned to the origin band, the excitation of one quantum of z-axis rotation and one associated hot band. The spacing of the bands and the rotational structure indicate a T-shaped vibrationally averaged structure with the NO molecule forming the top of the T. These findings are confirmed by high level ab initio calculations of the potential energy surfaces in planar symmetry. The deepest minimum is found for a T-shaped geometry on the A(")-surface. As a result the sum potential also has the global minimum for this structure. The different potential surfaces show several additional local minima at slightly higher energies indicating that the complex most likely will perform large amplitude motion even in its ground vibrational state. Nevertheless, as suggested by the measured spectra, the complex must, on average, spend a substantial amount of time near the T-shaped configuration.

Trp zipper folding kinetics by molecular dynamics and temperature-jump spectroscopy

PubMed Central

Snow, Christopher D.; Qiu, Linlin; Du, Deguo; Gai, Feng; Hagen, Stephen J.; Pande, Vijay S.

2004-01-01

We studied the microsecond folding dynamics of three β hairpins (Trp zippers 1–3, TZ1–TZ3) by using temperature-jump fluorescence and atomistic molecular dynamics in implicit solvent. In addition, we studied TZ2 by using time-resolved IR spectroscopy. By using distributed computing, we obtained an aggregate simulation time of 22 ms. The simulations included 150, 212, and 48 folding events at room temperature for TZ1, TZ2, and TZ3, respectively. The all-atom optimized potentials for liquid simulations (OPLSaa) potential set predicted TZ1 and TZ2 properties well; the estimated folding rates agreed with the experimentally determined folding rates and native conformations were the global potential-energy minimum. The simulations also predicted reasonable unfolding activation enthalpies. This work, directly comparing large simulated folding ensembles with multiple spectroscopic probes, revealed both the surprising predictive ability of current models as well as their shortcomings. Specifically, for TZ1–TZ3, OPLS for united atom models had a nonnative free-energy minimum, and the folding rate for OPLSaa TZ3 was sensitive to the initial conformation. Finally, we characterized the transition state; all TZs fold by means of similar, native-like transition-state conformations. PMID:15020773

Trp zipper folding kinetics by molecular dynamics and temperature-jump spectroscopy

NASA Astrophysics Data System (ADS)

Snow, Christopher D.; Qiu, Linlin; Du, Deguo; Gai, Feng; Hagen, Stephen J.; Pande, Vijay S.

2004-03-01

We studied the microsecond folding dynamics of three hairpins (Trp zippers 1-3, TZ1-TZ3) by using temperature-jump fluorescence and atomistic molecular dynamics in implicit solvent. In addition, we studied TZ2 by using time-resolved IR spectroscopy. By using distributed computing, we obtained an aggregate simulation time of 22 ms. The simulations included 150, 212, and 48 folding events at room temperature for TZ1, TZ2, and TZ3, respectively. The all-atom optimized potentials for liquid simulations (OPLSaa) potential set predicted TZ1 and TZ2 properties well; the estimated folding rates agreed with the experimentally determined folding rates and native conformations were the global potential-energy minimum. The simulations also predicted reasonable unfolding activation enthalpies. This work, directly comparing large simulated folding ensembles with multiple spectroscopic probes, revealed both the surprising predictive ability of current models as well as their shortcomings. Specifically, for TZ1-TZ3, OPLS for united atom models had a nonnative free-energy minimum, and the folding rate for OPLSaa TZ3 was sensitive to the initial conformation. Finally, we characterized the transition state; all TZs fold by means of similar, native-like transition-state conformations.

REopt Screenings Catalyze Development of Hundreds of Megawatts of Renewable Energy for Federal Agencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

The U.S. Department of Energy's (DOE's) Federal Energy Management Program (FEMP) offers project assistance to federal agencies, which often begins with a desktop screening to develop a prioritized portfolio of renewable energy project opportunities. FEMP uses the National Renewable Energy Laboratory's (NREL) REopt energy planning platform to quickly and efficiently screen potential renewable energy opportunities at a single site or across a range of sites. REopt helps organizations prioritize the most economically and technically viable projects for further study, and identifies the size and mix of technologies that meet the organization's goals at minimum cost, along with the optimal operatingmore » strategies.« less

Low energy isomers of (H{sub 2}O){sub 25} from a hierarchical method based on Monte Carlo temperature basin paving and molecular tailoring approaches benchmarked by MP2 calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahu, Nityananda; Gadre, Shridhar R., E-mail: gadre@iitk.ac.in, E-mail: sotiris.xantheas@pnnl.gov; Rakshit, Avijit

2014-10-28

We report new global minimum candidate structures for the (H{sub 2}O){sub 25} cluster that are lower in energy than the ones reported previously and correspond to hydrogen bonded networks with 42 hydrogen bonds and an interior, fully coordinated water molecule. These were obtained as a result of a hierarchical approach based on initial Monte Carlo Temperature Basin Paving sampling of the cluster's Potential Energy Surface with the Effective Fragment Potential, subsequent geometry optimization using the Molecular Tailoring Approach with the fragments treated at the second order Møller-Plesset (MP2) perturbation (MTA-MP2) and final refinement of the entire cluster at the MP2more » level of theory. The MTA-MP2 optimized cluster geometries, constructed from the fragments, were found to be within <0.5 kcal/mol from the minimum geometries obtained from the MP2 optimization of the entire (H{sub 2}O){sub 25} cluster. In addition, the grafting of the MTA-MP2 energies yields electronic energies that are within <0.3 kcal/mol from the MP2 energies of the entire cluster while preserving their energy rank order. Finally, the MTA-MP2 approach was found to reproduce the MP2 harmonic vibrational frequencies, constructed from the fragments, quite accurately when compared to the MP2 ones of the entire cluster in both the HOH bending and the OH stretching regions of the spectra.« less

Autonomous Sensor Motes Employing Liquid-Bearing Rotary Stages

DTIC Science & Technology

2014-03-06

breaks off (Fig. 27d) as shown in the sudden change in force, indicating rotor pull off. The minimum of each curve indicates the maximum tensile load...configuration, with marks on the curves at the minimum energy positions are shown in Fig. 39. The minimum energy positions from Fig. 39are plotted as...rates between 5 and 17 Hz rotation rate plotted vs. rotor eccentricity. The minimum energy positions are indicated on each curve . 3.3 Discussion

Orientations of dendritic growth during solidification

NASA Astrophysics Data System (ADS)

Lee, Dong Nyung

2017-03-01

Dendrites are crystalline forms which grow far from the limit of stability of the plane front and adopt an orientation which is as close as possible to the heat flux direction. Dendritic growth orientations for cubic metals, bct Sn, and hcp Zn, can be controlled by thermal conductivity, Young's modulus, and surface energy. The control factors have been elaborated. Since the dendrite is a single crystal, its properties such as thermal conductivity that influences the heat flux direction, the minimum Young's modulus direction that influences the strain energy minimization, and the minimum surface energy plane that influences the crystal/liquid interface energy minimization have been proved to control the dendritic growth direction. The dendritic growth directions of cubic metals are determined by the minimum Young's modulus direction and/or axis direction of symmetry of the minimum crystal surface energy plane. The dendritic growth direction of bct Sn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction. The primary dendritic growth direction of hcp Zn is determined by its maximum thermal conductivity direction and the minimum surface energy plane normal direction and the secondary dendrite arm direction of hcp Zn is normal to the primary dendritic growth direction.

Communication: A new ab initio potential energy surface for HCl-H2O, diffusion Monte Carlo calculations of D0 and a delocalized zero-point wavefunction.

PubMed

Mancini, John S; Bowman, Joel M

2013-03-28

We report a global, full-dimensional, ab initio potential energy surface describing the HCl-H2O dimer. The potential is constructed from a permutationally invariant fit, using Morse-like variables, to over 44,000 CCSD(T)-F12b∕aug-cc-pVTZ energies. The surface describes the complex and dissociated monomers with a total RMS fitting error of 24 cm(-1). The normal modes of the minima, low-energy saddle point and separated monomers, the double minimum isomerization pathway and electronic dissociation energy are accurately described by the surface. Rigorous quantum mechanical diffusion Monte Carlo (DMC) calculations are performed to determine the zero-point energy and wavefunction of the complex and the separated fragments. The calculated zero-point energies together with a De value calculated from CCSD(T) with a complete basis set extrapolation gives a D0 value of 1348 ± 3 cm(-1), in good agreement with the recent experimentally reported value of 1334 ± 10 cm(-1) [B. E. Casterline, A. K. Mollner, L. C. Ch'ng, and H. Reisler, J. Phys. Chem. A 114, 9774 (2010)]. Examination of the DMC wavefunction allows for confident characterization of the zero-point geometry to be dominant at the C(2v) double-well saddle point and not the C(s) global minimum. Additional support for the delocalized zero-point geometry is given by numerical solutions to the 1D Schrödinger equation along the imaginary-frequency out-of-plane bending mode, where the zero-point energy is calculated to be 52 cm(-1) above the isomerization barrier. The D0 of the fully deuterated isotopologue is calculated to be 1476 ± 3 cm(-1), which we hope will stand as a benchmark for future experimental work.

Computational studies of the helium-lithium hydride system

NASA Astrophysics Data System (ADS)

Taylor, Brian Keith

2000-12-01

We have computed an ab initio potential energy surface for the He-LiH system. We compute the He- LiH interaction energy at the CCSD(T) level using large correlation consistent atomic basis sets supplemented with bond functions. To capture the severe anisotropy of the He-LH potential, we interpolate our ab initio points in the angular direction with cubic splines, then expand the splines in terms of Legendre polynomials. We have constructed both a He-LiH rigid rotor potential and a complete He-LiH potential where the LiH bond length is allowed to change. The resulting potential surface has a unique shape. The He- LiH rigid rotor colinear geometry has a very attractive minimum of -176.7 cm-1, while the LiH-He colinear geometry has a local minimum of only -9.8 cm -1. Using our computed He-LiH potential energy surface, we investigate the collision dynamics of He-LiH. Using a totally quantum mechanical treatment of collisions dynamics, we compute both pure rotational and rovibrational state-to-state cross sections. We integrate our rovibrational cross sections over a Maxwell-Boltzmann distribution of energies to obtain temperature dependent vibrational excitation and relaxation rate constants. The vibrational excitation rate constants are very small for temperature below 400 K, but become significant at higher temperatures. These results suggests that He-LiH collisions probably were important in the very early Universe, especially in the larger primordial gas clouds. We also investigate the structure and dynamics of small HeN-LiH clusters using diffusion quantum Monte Carlo techniques. We find that three body effects are negligible, so we take the HeN-LiH potential to be a pairwise additive potential; we use the HFD-B3-FCI1 He-He potential of Aziz and Janzen [R. A. Aziz and A. R. Janzen, Phys. Rev. Lett. 74, 1586 (1995)] and our He-LiH potential. Because of the strong He-LiH attraction, one helium is always located in the attractive well at the lithium end of the LiH.

The effect of tidal forces on the minimum energy configurations of the full three-body problem

NASA Astrophysics Data System (ADS)

Levine, Edward

We investigate the evolution of minimum energy configurations for the Full Three Body Problem (3BP). A stable ternary asteroid system will gradually become unstable due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect and an unpredictable trajectory will ensue. Through the interaction of tidal torques, energy in the system will dissipate in the form of heat until a stable minimum energy configuration is reached. We present a simulation that describes the dynamical evolution of three bodies under the mutual effects of gravity and tidal torques. Simulations show that bodies do not get stuck in local minima and transition to the predicted minimum energy configuration.

Infrared, Raman and density functional characterization and structural study of 2-Nitro-2-phenyl-propane-1,3-diol

NASA Astrophysics Data System (ADS)

Kaya, Mehmet Fatih; Bağlayan, Özge; Kaya, Esma Güneş; Alver, Özgür

2017-12-01

Nitro compound and nitro derivatives are industrially important to produce rubber and agricultural chemicals. In this study, one of the promising derivatives of nitro compound 2-Nitro-2-phenyl-propane-1,3-diol (2NPP) is examined in detail. FT-Infrared and dispersive Raman spectra of 2NPP (C9H11NO4) were respectively recorded in 4000-10 cm-1 and 4000-100 cm-1. The bond distances and angles, conformational distributions, vibrational frequencies and the assignment of each mode, some thermodynamic parameters and reactivity descriptors: total energy, hardness, chemical potential, electrophilicity index, electronegativity, frontier orbitals energy gap of 2NPP were investigated by using DFT/B3LYP method with 6-31++G (d,p) basis set. In order to locate the global minimum on the potential energy surface of 2NPP, a beforehand conformational examinations were carried out using Spartan 10 along with semi-emprical PM6 method. The results of conformational analyses showed that there are five possible conformations having energies under 2 kcal/mol. Comparison of the theoretical and experimental results clearly indicates that density functional hybrid B3LYP/6-31++G (d,p) level of theory can be used to predict vibrational frequencies and structural parameters of 2NPP. Further, C1 geometry is considered to be the global minimum conformation of 2NPP.

Wang-Landau density of states based study of the folding-unfolding transition in the mini-protein Trp-cage (TC5b)

NASA Astrophysics Data System (ADS)

Singh, Priya; Sarkar, Subir K.; Bandyopadhyay, Pradipta

2014-07-01

We present the results of a high-statistics equilibrium study of the folding/unfolding transition for the 20-residue mini-protein Trp-cage (TC5b) in water. The ECEPP/3 force field is used and the interaction with water is treated by a solvent-accessible surface area method. A Wang-Landau type simulation is used to calculate the density of states and the conditional probabilities for the various values of the radius of gyration and the number of native contacts at fixed values of energy—along with a systematic check on their convergence. All thermodynamic quantities of interest are calculated from this information. The folding-unfolding transition corresponds to a peak in the temperature dependence of the computed specific heat. This is corroborated further by the structural signatures of folding in the distributions for radius of gyration and the number of native contacts as a function of temperature. The potentials of mean force are also calculated for these variables, both separately and jointly. A local free energy minimum, in addition to the global minimum, is found in a temperature range substantially below the folding temperature. The free energy at this second minimum is approximately 5 kBT higher than the value at the global minimum.

Possible metastable rhombohedral states of the bcc transition metals

NASA Astrophysics Data System (ADS)

Mehl, Michael; Finkenstadt, Daniel

2007-03-01

The energy E(c/a) for a bcc element stretched along its [001] axis (the Bain path) has a minimum at c/a = 1, a maximum at c/a = √2, and an elastically unstable local minimum at c/a > √2. A rhombohedral strain is an alternative method of connecting the bcc and fcc structures. The primitive lattice keeps R3m symmetry, with the angle α changing from 109.4^o (bcc), to 90^o (simple cubic), to 60^o (fcc). We studied this path for the non-magnetic bcc transition metals (V, Nb, Mo, Ta, and W) using both a full-potential LAPW and PAW VASP. Except for Ta, the energy E(α) has a local maximum at α=60^o, with local minima near 55^o and 70^o, the later having lower energy. We studied the elastic stability of the 70^o minimum structure. Only W is elastically stable in this structure, with the smallest eigenvalue of the elastic tensor at 4 GPa, while the other three elements are unstable. We discuss the possibility that Tungsten is actually metastable in this structure. We also consider the possible epitaxial growth of this structure. M. J. Mehl, A. Aguayo, L. L. Boyer, and R. De Coss, Phys. Rev. B 70, 014105 (2004).

Relation between the Dynamics of Glassy Clusters and Characteristic Features of their Energy Landscape

NASA Astrophysics Data System (ADS)

De, Sandip; Schaefer, Bastian; Sadeghi, Ali; Sicher, Michael; Kanhere, D. G.; Goedecker, Stefan

2014-02-01

Based on a recently introduced metric for measuring distances between configurations, we introduce distance-energy (DE) plots to characterize the potential energy surface of clusters. Producing such plots is computationally feasible on the density functional level since it requires only a few hundred stable low energy configurations including the global minimum. By using standard criteria based on disconnectivity graphs and the dynamics of Lennard-Jones clusters, we show that the DE plots convey the necessary information about the character of the potential energy surface and allow us to distinguish between glassy and nonglassy systems. We then apply this analysis to real clusters at the density functional theory level and show that both glassy and nonglassy clusters can be found in simulations. It turns out that among our investigated clusters only those can be synthesized experimentally which exhibit a nonglassy landscape.

Safety in the Chemical Laboratory

ERIC Educational Resources Information Center

Coffee, Robert D.

1972-01-01

The author discusses a system for establishing the relative potential of a chemical to release energy suddenly and to indicate release. This system is applicable to chemical storage and transportation. The system is based upon three simple tests requiring a minimum sample (1 go or 1 ml): (1) computation, (2) impact sensitivity, and (3) thermal…

Tidal evolution in close binary systems.

NASA Technical Reports Server (NTRS)

Kopal, Z.

1972-01-01

Mathematical outline of the theory of tidal evolution in close binary systems of secularly constant total momentum. Following a general outline of the problem the basic expressions for the energy and momenta of close binaries consisting of components of arbitrary internal structure are established, and the maximum and minimum values of the energy (kinetic and potential) which such systems can attain for a given amount of total momentum are investigated. These results are compared with the actual facts encountered in binaries with components whose internal structure (and, therefore, rotational momenta) are known from evidence furnished by the observed rates of apsidal advance. The results show that all such systems whether of detached or semidetached type - disclose that more than 99% of their total momenta are stored in the orbital momentum. The sum of the rotational momenta of the constituent components amounts to less than 1% of the total -a situation characteristic of a state close to the minimum energy for given total momentum.

Amino acids at water-vapor interfaces: surface activity and orientational ordering.

PubMed

Vöhringer-Martinez, Esteban; Toro-Labbé, Alejandro

2010-10-14

The surface activity and orientational ordering of amino acids at water-vapor interfaces were studied with molecular dynamics simulations in combination with thermodynamic integration and umbrella sampling. Asparagine, representing amino acids with polar side chains, displays no surface activity. Tryptophan, in contrast, with its hydrophobic indole ring as side chain unveils a free energy minimum at the water-vapor interface, which lies 6 kJ/mol under the hydration free energy. To study the orientational ordering of tryptophan along the interface, the order parameter was calculated. At the free energy minimum and at the Gibbs dividing surface, the order parameter reveals a parallel alignment of the indole ring with the water surface exposing the π-system to electrophiles in the hydrophobic phase and indicating polarization dependent spectroscopy. In the vicinity of this position a perpendicular orientation is obtained. The surface excess, calculated from the potential of mean force along the interface, is in excellent agreement with experimental measurements.

Shear and compression buckling analysis for anisotropic panels with centrally located elliptical cutouts

NASA Technical Reports Server (NTRS)

Britt, V. O.

1993-01-01

An approximate analysis for buckling of biaxial- and shear-loaded anisotropic panels with centrally located elliptical cutouts is presented in the present paper. The analysis is composed of two parts, a prebuckling analysis and a buckling analysis. The prebuckling solution is determined using Lekhnitskii's complex variable equations of plane elastostatics combined with a Laurent series approximation and a boundary collocation method. The buckling solution is obtained using the principle of minimum potential energy. A by-product of the minimum potential energy equation is an integral equation which is solved using Gaussian quadrature. Comparisons with documented experimental results and finite element analyses indicate that the approximate analysis accurately predicts the buckling loads of square biaxial- and shear-loaded panels having elliptical cutouts with major axes up to sixty percent of the panel width. Results of a parametric study are presented for shear- and compression-loaded rectangular anisotropic panels with elliptical cutouts. The effects of panel aspect ratio, cutout shape, cutout size, cutout orientation, laminate anisotropy, and combined loading on the buckling load are examined.

SASS: A symmetry adapted stochastic search algorithm exploiting site symmetry

NASA Astrophysics Data System (ADS)

Wheeler, Steven E.; Schleyer, Paul v. R.; Schaefer, Henry F.

2007-03-01

A simple symmetry adapted search algorithm (SASS) exploiting point group symmetry increases the efficiency of systematic explorations of complex quantum mechanical potential energy surfaces. In contrast to previously described stochastic approaches, which do not employ symmetry, candidate structures are generated within simple point groups, such as C2, Cs, and C2v. This facilitates efficient sampling of the 3N-6 Pople's dimensional configuration space and increases the speed and effectiveness of quantum chemical geometry optimizations. Pople's concept of framework groups [J. Am. Chem. Soc. 102, 4615 (1980)] is used to partition the configuration space into structures spanning all possible distributions of sets of symmetry equivalent atoms. This provides an efficient means of computing all structures of a given symmetry with minimum redundancy. This approach also is advantageous for generating initial structures for global optimizations via genetic algorithm and other stochastic global search techniques. Application of the SASS method is illustrated by locating 14 low-lying stationary points on the cc-pwCVDZ ROCCSD(T) potential energy surface of Li5H2. The global minimum structure is identified, along with many unique, nonintuitive, energetically favorable isomers.

ABCluster: the artificial bee colony algorithm for cluster global optimization.

PubMed

Zhang, Jun; Dolg, Michael

2015-10-07

Global optimization of cluster geometries is of fundamental importance in chemistry and an interesting problem in applied mathematics. In this work, we introduce a relatively new swarm intelligence algorithm, i.e. the artificial bee colony (ABC) algorithm proposed in 2005, to this field. It is inspired by the foraging behavior of a bee colony, and only three parameters are needed to control it. We applied it to several potential functions of quite different nature, i.e., the Coulomb-Born-Mayer, Lennard-Jones, Morse, Z and Gupta potentials. The benchmarks reveal that for long-ranged potentials the ABC algorithm is very efficient in locating the global minimum, while for short-ranged ones it is sometimes trapped into a local minimum funnel on a potential energy surface of large clusters. We have released an efficient, user-friendly, and free program "ABCluster" to realize the ABC algorithm. It is a black-box program for non-experts as well as experts and might become a useful tool for chemists to study clusters.

Potential energy surfaces of the low-lying electronic states of the Li + LiCs system

NASA Astrophysics Data System (ADS)

Jasik, P.; Kilich, T.; Kozicki, J.; Sienkiewicz, J. E.

2018-03-01

Ab initio quantum chemistry calculations are performed for the mixed alkali triatomic system. Global minima of the ground and first excited doublet states of the trimer are found and Born-Oppenheimer potential energy surfaces of the Li atom interacting with the LiCs molecule were calculated for these states. The lithium atom is placed at various distances and bond angles from the lithium-caesium dimer. Three-body nonadditive forces of the Li2Cs molecule in the global minimum are investigated. Dimer-atom interactions are found to be strongly attractive and may be important in the experiments, particularly involving cold alkali polar dimers.

Accelerated molecular dynamics and protein conformational change: a theoretical and practical guide using a membrane embedded model neurotransmitter transporter.

PubMed

Gedeon, Patrick C; Thomas, James R; Madura, Jeffry D

2015-01-01

Molecular dynamics simulation provides a powerful and accurate method to model protein conformational change, yet timescale limitations often prevent direct assessment of the kinetic properties of interest. A large number of molecular dynamic steps are necessary for rare events to occur, which allow a system to overcome energy barriers and conformationally transition from one potential energy minimum to another. For many proteins, the energy landscape is further complicated by a multitude of potential energy wells, each separated by high free-energy barriers and each potentially representative of a functionally important protein conformation. To overcome these obstacles, accelerated molecular dynamics utilizes a robust bias potential function to simulate the transition between different potential energy minima. This straightforward approach more efficiently samples conformational space in comparison to classical molecular dynamics simulation, does not require advanced knowledge of the potential energy landscape and converges to the proper canonical distribution. Here, we review the theory behind accelerated molecular dynamics and discuss the approach in the context of modeling protein conformational change. As a practical example, we provide a detailed, step-by-step explanation of how to perform an accelerated molecular dynamics simulation using a model neurotransmitter transporter embedded in a lipid cell membrane. Changes in protein conformation of relevance to the substrate transport cycle are then examined using principle component analysis.

Warm Body Temperature Facilitates Energy Efficient Cortical Action Potentials

PubMed Central

Yu, Yuguo; Hill, Adam P.; McCormick, David A.

2012-01-01

The energy efficiency of neural signal transmission is important not only as a limiting factor in brain architecture, but it also influences the interpretation of functional brain imaging signals. Action potential generation in mammalian, versus invertebrate, axons is remarkably energy efficient. Here we demonstrate that this increase in energy efficiency is due largely to a warmer body temperature. Increases in temperature result in an exponential increase in energy efficiency for single action potentials by increasing the rate of Na+ channel inactivation, resulting in a marked reduction in overlap of the inward Na+, and outward K+, currents and a shortening of action potential duration. This increase in single spike efficiency is, however, counterbalanced by a temperature-dependent decrease in the amplitude and duration of the spike afterhyperpolarization, resulting in a nonlinear increase in the spike firing rate, particularly at temperatures above approximately 35°C. Interestingly, the total energy cost, as measured by the multiplication of total Na+ entry per spike and average firing rate in response to a constant input, reaches a global minimum between 37–42°C. Our results indicate that increases in temperature result in an unexpected increase in energy efficiency, especially near normal body temperature, thus allowing the brain to utilize an energy efficient neural code. PMID:22511855

A harmonic adiabatic approximation to calculate highly excited vibrational levels of ``floppy molecules''

NASA Astrophysics Data System (ADS)

Lauvergnat, David; Nauts, André; Justum, Yves; Chapuisat, Xavier

2001-04-01

The harmonic adiabatic approximation (HADA), an efficient and accurate quantum method to calculate highly excited vibrational levels of molecular systems, is presented. It is well-suited to applications to "floppy molecules" with a rather large number of atoms (N>3). A clever choice of internal coordinates naturally suggests their separation into active, slow, or large amplitude coordinates q', and inactive, fast, or small amplitude coordinates q″, which leads to an adiabatic (or Born-Oppenheimer-type) approximation (ADA), i.e., the total wave function is expressed as a product of active and inactive total wave functions. However, within the framework of the ADA, potential energy data concerning the inactive coordinates q″ are required. To reduce this need, a minimum energy domain (MED) is defined by minimizing the potential energy surface (PES) for each value of the active variables q', and a quadratic or harmonic expansion of the PES, based on the MED, is used (MED harmonic potential). In other words, the overall picture is that of a harmonic valley about the MED. In the case of only one active variable, we have a minimum energy path (MEP) and a MEP harmonic potential. The combination of the MED harmonic potential and the adiabatic approximation (harmonic adiabatic approximation: HADA) greatly reduces the size of the numerical computations, so that rather large molecules can be studied. In the present article however, the HADA is applied to our benchmark molecule HCN/CNH, to test the validity of the method. Thus, the HADA vibrational energy levels are compared and are in excellent agreement with the ADA calculations (adiabatic approximation with the full PES) of Light and Bačić [J. Chem. Phys. 87, 4008 (1987)]. Furthermore, the exact harmonic results (exact calculations without the adiabatic approximation but with the MEP harmonic potential) are compared to the exact calculations (without any sort of approximation). In addition, we compare the densities of the bending motion during the HCN/CNH isomerization, computed with the HADA and the exact wave function.

Oxygen enhanced switching to combustion of lower rank fuels

DOEpatents

Kobayashi, Hisashi; Bool, III, Lawrence E.; Wu, Kuang Tsai

2004-03-02

A furnace that combusts fuel, such as coal, of a given minimum energy content to obtain a stated minimum amount of energy per unit of time is enabled to combust fuel having a lower energy content, while still obtaining at least the stated minimum energy generation rate, by replacing a small amount of the combustion air fed to the furnace by oxygen. The replacement of oxygen for combustion air also provides reduction in the generation of NOx.

Design and Analysis of Optimal Ascent Trajectories for Stratospheric Airships

NASA Astrophysics Data System (ADS)

Mueller, Joseph Bernard

Stratospheric airships are lighter-than-air vehicles that have the potential to provide a long-duration airborne presence at altitudes of 18-22 km. Designed to operate on solar power in the calm portion of the lower stratosphere and above all regulated air traffic and cloud cover, these vehicles represent an emerging platform that resides between conventional aircraft and satellites. A particular challenge for airship operation is the planning of ascent trajectories, as the slow moving vehicle must traverse the high wind region of the jet stream. Due to large changes in wind speed and direction across altitude and the susceptibility of airship motion to wind, the trajectory must be carefully planned, preferably optimized, in order to ensure that the desired station be reached within acceptable performance bounds of flight time and energy consumption. This thesis develops optimal ascent trajectories for stratospheric airships, examines the structure and sensitivity of these solutions, and presents a strategy for onboard guidance. Optimal ascent trajectories are developed that utilize wind energy to achieve minimum-time and minimum-energy flights. The airship is represented by a three-dimensional point mass model, and the equations of motion include aerodynamic lift and drag, vectored thrust, added mass effects, and accelerations due to mass flow rate, wind rates, and Earth rotation. A representative wind profile is developed based on historical meteorological data and measurements. Trajectory optimization is performed by first defining an optimal control problem with both terminal and path constraints, then using direct transcription to develop an approximate nonlinear parameter optimization problem of finite dimension. Optimal ascent trajectories are determined using SNOPT for a variety of upwind, downwind, and crosswind launch locations. Results of extensive optimization solutions illustrate definitive patterns in the ascent path for minimum time flights across varying launch locations, and show that significant energy savings can be realized with minimum-energy flights, compared to minimum-time time flights, given small increases in flight time. The performance of the optimal trajectories are then studied with respect to solar energy production during ascent, as well as sensitivity of the solutions to small changes in drag coefficient and wind model parameters. Results of solar power model simulations indicate that solar energy is sufficient to power ascent flights, but that significant energy loss can occur for certain types of trajectories. Sensitivity to the drag and wind model is approximated through numerical simulations, showing that optimal solutions change gradually with respect to changing wind and drag parameters and providing deeper insight into the characteristics of optimal airship flights. Finally, alternative methods are developed to generate near-optimal ascent trajectories in a manner suitable for onboard implementation. The structures and characteristics of previously developed minimum-time and minimum-energy ascent trajectories are used to construct simplified trajectory models, which are efficiently solved in a smaller numerical optimization problem. Comparison of these alternative solutions to the original SNOPT solutions show excellent agreement, suggesting the alternate formulations are an effective means to develop near-optimal solutions in an onboard setting.

Single-Walled Carbon Nanotubes Modulate the B- to A-DNA Transition

PubMed Central

2015-01-01

We study the conformational equilibrium between B-to-A forms of ds-DNA adsorbed onto a single-walled carbon nanotube (SWNT) using free energy profile calculations based on all-atom molecular dynamics simulations. The potential of mean force (PMF) of the B-to-A transition of ds-DNA in the presence of an uncharged (10,0) carbon nanotube for two dodecamers with poly-AT or poly-GC sequences is calculated as a function of a root-mean-square-distance (ΔRMSD) difference metric for the B-to-A transition. The calculations reveal that in the presence of a SWNT DNA favors B-form DNA significantly in both poly-GC and poly-AT sequences. Furthermore, the poly-AT DNA:SWNT complex shows a higher energy penalty for adopting an A-like conformation than poly-GC DNA:SWNT by several kcal/mol. The presence of a SWNT on either poly-AT or poly-GC DNA affects the PMF of the transition such that the B form is favored by as much as 10 kcal/mol. In agreement with published data, we find a potential energy minimum between A and B-form DNA at ΔRMSD ≈ −1.5 Å and that the presence of the SWNT moves this minimum by as much as ΔRMSD = 3 Å. PMID:25553205

Theoretical study of the interaction of N/sub 2/ with water molecules. (H/sub 2/O)/sub n/:N/sub 2/, n = 1--8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtiss, L.A.; Eisgruber, C.L.

1984-03-01

Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H/sub 2/O molecule with N/sub 2/. The potential energy surface for H/sub 2/O:N/sub 2/ is found to have a minimum corresponding to a HOH xxx N/sub 2/ structure with a weak (<2 kcal mol/sup -1/) hydrogen bond. A second, less stable, configuration corresponding to a H/sub 2/O xxx N/sub 2/ structure with N/sub 2/ bonded side on to the oxygen of H/sub 2/O was found to be either a minimum or a saddle point in the potential energy surface depending on themore » level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H/sub 2/O molecules with N/sub 2/. Two types of clusters, one containing only HOH xxx N/sub 2/ interactions and the other containing both HOH xxxN/sub 2/ and H/sub 2/O xxx N/sub 2/ interactions, were investigated for (N/sub 2/:(H/sub 2/O)/sub n/, n = 2--8).« less

Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel

NASA Astrophysics Data System (ADS)

Kurosaki, Yuzuru; Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel

2009-07-01

Quantum wave packet optimal control simulations with intense laser pulses have been carried out for studying molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open→cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O2+O asymptote on the O3 ground-state A1' potential energy surface. Energetically, the cyclic ring isomer, the TS barrier, and the O2+O dissociation channel lie at ˜0.05, ˜0.086, and ˜0.037 hartree above the open isomer, respectively. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum. The quick transition of the ozone wave packet avoids detrimental leakage into the competing O2+O channel. It is possible to obtain weaker optimal laser fields, resulting in slower transfer of the wave packets over the TS, when a reduced level of isomerization is satisfactory.

Dynamic Electron Correlation Effects on the Ground State Potential Energy Surface of a Retinal Chromophore Model.

PubMed

Gozem, Samer; Huntress, Mark; Schapiro, Igor; Lindh, Roland; Granovsky, Alexander A; Angeli, Celestino; Olivucci, Massimo

2012-11-13

The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures. This implies that dynamic electron correlation may have a large effect on the shape of the force fields driving its reactivity. To investigate this effect, we focus on mapping the potential energy for three paths located along the ground state CASSCF potential energy surface of the penta-2,4-dieniminium cation taken as a minimal model of the retinal chromophore. The first path spans the bond length alternation coordinate and intercepts a conical intersection point. The other two are minimum energy paths along two distinct but kinetically competitive thermal isomerization coordinates. We show that the effect of introducing the missing dynamic electron correlation variationally (with MRCISD) and perturbatively (with the CASPT2, NEVPT2, and XMCQDPT2 methods) leads, invariably, to a stabilization of the regions with charge transfer character and to a significant reshaping of the reference CASSCF potential energy surface and suggesting a change in the dominating isomerization mechanism. The possible impact of such a correction on the photoisomerization of the retinal chromophore is discussed.

Sphalerons in composite and nonstandard Higgs models

NASA Astrophysics Data System (ADS)

Spannowsky, Michael; Tamarit, Carlos

2017-01-01

After the discovery of the Higgs boson and the rather precise measurement of all electroweak boson's masses the local structure of the electroweak symmetry breaking potential is already quite well established. However, despite being a key ingredient to a fundamental understanding of the underlying mechanism of electroweak symmetry breaking, the global structure of the electroweak potential remains entirely unknown. The existence of sphalerons, unstable solutions of the classical action of motion that are interpolating between topologically distinct vacua, is a direct consequence of the Standard Model's SU (2 )L gauge group. Nevertheless, the sphaleron energy depends on the shape of the Higgs potential away from the minimum and can therefore be a litmus test for its global structure. Focusing on two scenarios, the minimal composite Higgs model SO (5 )/SO (4 ) or an elementary Higgs with a deformed electroweak potential, we calculate the change of the sphaleron energy compared to the Standard Model prediction. We find that the sphaleron energy would have to be measured to O (10 )% accuracy to exclude sizeable global deviations from the Standard Model Higgs potential. We further find that because of the periodicity of the scalar potential in composite Higgs models a second sphaleron branch with larger energy arises.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sullivan, Patrick; Logan, Jeffrey; Bird, Lori

This paper analyzes potential impacts of proposed national renewable electricity standard (RES) legislation. An RES is a mandate requiring certain electricity retailers to provide a minimum share of their electricity sales from qualifying renewable power generation. The analysis focuses on draft bills introduced individually by Senator Jeff Bingaman and Representative Edward Markey, and jointly by Representative Henry Waxman and Markey. The analysis uses NREL's Regional Energy Deployment System (ReEDS) model to evaluate the impacts of the proposed RES requirements on the U.S. energy sector in four scenarios.

Dropping a Particle Out of a Roller Coaster

DTIC Science & Technology

2014-04-24

of the kinetic energy gained from the gravitational potential energy lost. Both friction and air drag are neglected. Point P marks a local minimum of...be that of a person swinging on the end of a rope like a simple pendulum and then releasing it and flying through the air [3]. • Reminiscent of a...shape described by functions such as a clothoid [7] to minimize any abrupt changes in the centripetal acceleration of the riders. The analysis can be

Optical Boron Nitride Insulator Erosion Characterization of a 200 W Xenon Hall Thruster

DTIC Science & Technology

2005-05-01

Hall thruster boron nitride insulator is evaluated as a diagnostic for real-time evaluation of thruster insulator erosion. Three Hall thruster plasma control variables are examined: ion energy (discharge potential), ion flux (propellant flow), and plasma conductivity (magnetic field strength). The boron emission, and hence the insulator erosion rate, varies linearly with ion energy and ion flux. A minimum erosion rate appears at intermediate magnetic field strengths. This may indicate that local plasma conductivity significantly affects the divergence

Minimum Energy Pathways for Chemical Reactions

NASA Technical Reports Server (NTRS)

Walch, S. P.; Langhoff, S. R. (Technical Monitor)

1995-01-01

Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives useful results for a number of chemically important systems. The talk will focus on a number of applications to reactions leading to NOx and soot formation in hydrocarbon combustion.

Ab Initio and Analytic Intermolecular Potentials for Ar-CF₄

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vayner, Grigoriy; Alexeev, Yuri; Wang, Jiangping

2006-03-09

Ab initio calculations at the CCSD(T) level of theory are performed to characterize the Ar + CF ₄ intermolecular potential. Extensive calculations, with and without a correction for basis set superposition error (BSSE), are performed with the cc-pVTZ basis set. Additional calculations are performed with other correlation consistent (cc) basis sets to extrapolate the Ar---CF₄potential energy minimum to the complete basis set (CBS) limit. Both the size of the basis set and BSSE have substantial effects on the Ar + CF₄ potential. Calculations with the cc-pVTZ basis set and without a BSSE correction, appear to give a good representation ofmore » the potential at the CBS limit and with a BSSE correction. In addition, MP2 theory is found to give potential energies in very good agreement with those determined by the much higher level CCSD(T) theory. Two analytic potential energy functions were determined for Ar + CF₄by fitting the cc-pVTZ calculations both with and without a BSSE correction. These analytic functions were written as a sum of two body potentials and excellent fits to the ab initio potentials were obtained by representing each two body interaction as a Buckingham potential.« less

Theoretical studies of potential energy surface and rotational spectra of Xe -H2O van der Waals complex

NASA Astrophysics Data System (ADS)

Wang, Lin; Yang, Minghui

2008-11-01

In this work we report an ab initio intermolecular potential energy surface and theoretical spectroscopic studies for Xe -H2O complex. The ab initio energies are calculated with CCSD(T) method and large basis sets (aug-cc-pVQZ for H and O and aug-cc-pVQZ-PP for Xe) augmented by a {3s3p2d2f1g} set of bond functions. This potential energy surface has a global minimum corresponding to a planar and nearly linear hydrogen bonded configuration with a well depth of 192.5cm-1 at intermolecular distance of 4.0Å, which is consistent with the previous determined potential by Wen and Jäger [J. Phys. Chem. A 110, 7560 (2006)]. The bound state calculations have been performed for the complex by approximating the water molecule as a rigid rotor. The theoretical rotational transition frequencies, isotopic shifts, nuclear quadrupole coupling constants, and structure parameters are in good agreement with the experimental observed values. The wavefunctions are analyzed to understand the dynamics of the ground and the first excited states.

Dynamics Sampling in Transition Pathway Space.

PubMed

Zhou, Hongyu; Tao, Peng

2018-01-09

The minimum energy pathway contains important information describing the transition between two states on a potential energy surface (PES). Chain-of-states methods were developed to efficiently calculate minimum energy pathways connecting two stable states. In the chain-of-states framework, a series of structures are generated and optimized to represent the minimum energy pathway connecting two states. However, multiple pathways may exist connecting two existing states and should be identified to obtain a full view of the transitions. Therefore, we developed an enhanced sampling method, named as the direct pathway dynamics sampling (DPDS) method, to facilitate exploration of a PES for multiple pathways connecting two stable states as well as addition minima and their associated transition pathways. In the DPDS method, molecular dynamics simulations are carried out on the targeting PES within a chain-of-states framework to directly sample the transition pathway space. The simulations of DPDS could be regulated by two parameters controlling distance among states along the pathway and smoothness of the pathway. One advantage of the chain-of-states framework is that no specific reaction coordinates are necessary to generate the reaction pathway, because such information is implicitly represented by the structures along the pathway. The chain-of-states setup in a DPDS method greatly enhances the sufficient sampling in high-energy space between two end states, such as transition states. By removing the constraint on the end states of the pathway, DPDS will also sample pathways connecting minima on a PES in addition to the end points of the starting pathway. This feature makes DPDS an ideal method to directly explore transition pathway space. Three examples demonstrate the efficiency of DPDS methods in sampling the high-energy area important for reactions on the PES.

The fcc - bcc structural transition: I. A band theoretical study for Li, K, Rb, Ca, Sr, and the transition metals Ti and V

NASA Astrophysics Data System (ADS)

Sliwko, V. L.; Mohn, P.; Schwarz, K.; Blaha, P.

1996-02-01

Employing a high-precision band structure method (FP LAPW - full potential linearized augmented plane wave) we calculate the total energy variation along the tetragonal distortion path connecting the body centred cubic (bcc) and the face centred cubic (fcc) structures. The total energy along this Bain transformation is calculated, varying c/a and volume, providing a first-principles energy surface which has two minima as a function of c/a. These are shallow and occur for the sp metals at the two cubic structures, while Ti (V) has a minimum at fcc (bcc) but a saddle point (i.e. a minimum in volume and a maximum with respect to c/a) at the other cubic structure. These features can be analysed in terms of an interplay between the Madelung contribution and the band energies. Our total energy results allow us to calculate the elastic constants 0953-8984/8/7/006/img1 and 0953-8984/8/7/006/img2 and to study the influence of pressure on the phase stability. These energy surfaces will be used in part II of this paper to investigate finite-temperature effects by mapping them to a Landau - Ginzburg expansion.

Is the tautochrone curve unique?

NASA Astrophysics Data System (ADS)

Terra, Pedro; de Melo e Souza, Reinaldo; Farina, C.

2016-12-01

We show that there are an infinite number of tautochrone curves in addition to the cycloid solution first obtained by Christiaan Huygens in 1658. We begin by reviewing the inverse problem of finding the possible potential energy functions that lead to periodic motions of a particle whose period is a given function of its mechanical energy. There are infinitely many such solutions, called "sheared" potentials. As an interesting example, we show that a Pöschl-Teller potential and the one-dimensional Morse potentials are sheared relative to one another for negative energies, clarifying why they share the same oscillation periods for their bounded solutions. We then consider periodic motions of a particle sliding without friction over a track around its minimum under the influence of a constant gravitational field. After a brief historical survey of the tautochrone problem we show that, given the oscillation period, there is an infinity of tracks that lead to the same period. As a bonus, we show that there are infinitely many tautochrones.

Wave function delocalization and large-amplitude vibrations of helium on corrugated aromatic microsurfaces: tetracene.He and pentacene.He van der Waals complexes.

PubMed

Xu, Minzhong; Bacić, Zlatko

2007-08-09

We report accurate quantum three-dimensional calculations of highly excited intermolecular vibrational states of the van der Waals (vdW) complexes tetracene.He and pentacene.He in the S1 excited electronic state. The aromatic molecules were taken to be rigid and the intermolecular potential energy surfaces (IPESs) were modeled as a sum of atom-atom Lennard-Jones pair potentials. The IPESs are corrugated in the direction of the long (x) axis of the aromatic molecules, due to the presence of the symmetrically equivalent global double minimum for tetracene.He, and a triple minimum (central global minimum and two equivalent local minima) for pentacene.He, on each side of the aromatic plane. Both IPESs have two additional minor equivalent local minima further away from the center of the molecule. The vdW vibrational states analyzed in this work cover about 80% of the well depths of the IPESs. The mode coupling is generally weak for those states whose out-of-plane (z) mode is unexcited. However, the z-mode fundamental is strongly coupled to the short-axis (y) in-plane mode, so that the pure z-mode excitation could not be identified. The He atom exhibits large in-plane spatial delocalizaton already in the ground vdW vibrational state, which increases rapidly upon the excitation of the in-plane x and y modes, with little hindrance by the corrugation of the aromatic microsurfaces. For the vdW vibrational energies considered, the He atom spatial delocalization reaches Deltax and Deltay values of approximately 5 and 4 A, respectively, and is limited only by the finite size of the aromatic substrates. Side-crossing delocalization of the wave functions on both sides of the molecular plane is found at excitation energies >30 cm(-1), giving rise to the energy splittings of the pairs of states symmetric/antisymmetric with respect to the aromatic plane; the splittings show strong vdW vibrational mode specificity.

Experimental investigations of the minimum ignition energy and the minimum ignition temperature of inert and combustible dust cloud mixtures.

PubMed

Addai, Emmanuel Kwasi; Gabel, Dieter; Krause, Ulrich

2016-04-15

The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety (moderation). This is achieved by adding an inert material to a highly combustible material in order to decrease the ignition sensitivity of the combustible dust. The presented paper deals with the experimental investigation of the influence of adding an inert dust on the minimum ignition energy and the minimum ignition temperature of the combustible/inert dust mixtures. The experimental investigation was done in two laboratory scale equipment: the Hartmann apparatus and the Godbert-Greenwald furnace for the minimum ignition energy and the minimum ignition temperature test respectively. This was achieved by mixing various amounts of three inert materials (magnesium oxide, ammonium sulphate and sand) and six combustible dusts (brown coal, lycopodium, toner, niacin, corn starch and high density polyethylene). Generally, increasing the inert materials concentration increases the minimum ignition energy as well as the minimum ignition temperatures until a threshold is reached where no ignition was obtained. The permissible range for the inert mixture to minimize the ignition risk lies between 60 to 80%. Copyright © 2016 Elsevier B.V. All rights reserved.

Cosmic acceleration from M theory on twisted spaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neupane, Ishwaree P.; Wiltshire, David L.

2005-10-15

In a recent paper [I. P. Neupane and D. L. Wiltshire, Phys. Lett. B 619, 201 (2005).] we have found a new class of accelerating cosmologies arising from a time-dependent compactification of classical supergravity on product spaces that include one or more geometric twists along with nontrivial curved internal spaces. With such effects, a scalar potential can have a local minimum with positive vacuum energy. The existence of such a minimum generically predicts a period of accelerated expansion in the four-dimensional Einstein conformal frame. Here we extend our knowledge of these cosmological solutions by presenting new examples and discuss themore » properties of the solutions in a more general setting. We also relate the known (asymptotic) solutions for multiscalar fields with exponential potentials to the accelerating solutions arising from simple (or twisted) product spaces for internal manifolds.« less

Pseudo paths towards minimum energy states in network dynamics

NASA Astrophysics Data System (ADS)

Hedayatifar, L.; Hassanibesheli, F.; Shirazi, A. H.; Vasheghani Farahani, S.; Jafari, G. R.

2017-10-01

The dynamics of networks forming on Heider balance theory moves towards lower tension states. The condition derived from this theory enforces agents to reevaluate and modify their interactions to achieve equilibrium. These possible changes in network's topology can be considered as various paths that guide systems to minimum energy states. Based on this theory the final destination of a system could reside on a local minimum energy, ;jammed state;, or the global minimum energy, balanced states. The question we would like to address is whether jammed states just appear by chance? Or there exist some pseudo paths that bound a system towards a jammed state. We introduce an indicator to suspect the location of a jammed state based on the Inverse Participation Ratio method (IPR). We provide a margin before a local minimum where the number of possible paths dramatically drastically decreases. This is a condition that proves adequate for ending up on a jammed states.

Characterization of the Minimum Energy Path for the Reaction of Singlet Methylene with N2: The Role of Singlet Methylene in Prompt NO

NASA Technical Reports Server (NTRS)

Walch, Stephen P.

1995-01-01

We report calculations of the minimum energy pathways connecting CH2 + N2 to diazomethane and diazirine, for the rearrangement of diazirine to diazomethane, for the dissociation of diazirine to HCN2+H, and of diazomethane to CH2N+N. The calculations use Complete Active Space Self-Consistent Field (CASSCF) derivative methods to characterize the stationary points and Internally Contracted Configuration Interaction (ICCI) to determine the energetics. The calculations suggest a potential new source of prompt NO from the reaction CH2 with N2 to give diazirine, and subsequent reaction of diazirine with hydrogen abstracters to form doublet HCN2, which leads to HCN+N(S-4) on the previously studied CH+N2 surface. The calculations also predict accurate 0 K heats of formation of 77.7 kcal/mol and 68.0 kcal/mol for diazirine and diazomethane, respectively.

Continuum Mean-Field Theories for Molecular Fluids, and Their Validity at the Nanoscale

NASA Astrophysics Data System (ADS)

Hanna, C. B.; Peyronel, F.; MacDougall, C.; Marangoni, A.; Pink, D. A.; AFMNet-NCE Collaboration

2011-03-01

We present a calculation of the physical properties of solid triglyceride particles dispersed in an oil phase, using atomic- scale molecular dynamics. Significant equilibrium density oscillations in the oil appear when the interparticle distance, d , becomes sufficiently small, with a global minimum in the free energy found at d ~ 1.4 nm. We compare the simulation values of the Hamaker coefficient with those of models which assume that the oil is a homogeneous continuum: (i) Lifshitz theory, (ii) the Fractal Model, and (iii) a Lennard-Jones 6-12 potential model. The last-named yields a minimum in the free energy at d ~ 0.26 nm. We conclude that, at the nanoscale, continuum Lifshitz theory and other continuum mean-field theories based on the assumption of homogeneous fluid density can lead to erroneous conclusions. CBH supported by NSF DMR-0906618. DAP supported by NSERC. This work supported by AFMNet-NCE.

Research on theoretical optimization and experimental verification of minimum resistance hull form based on Rankine source method

NASA Astrophysics Data System (ADS)

Zhang, Bao-Ji; Zhang, Zhu-Xin

2015-09-01

To obtain low resistance and high efficiency energy-saving ship, minimum total resistance hull form design method is studied based on potential flow theory of wave-making resistance and considering the effects of tail viscous separation. With the sum of wave resistance and viscous resistance as objective functions and the parameters of B-Spline function as design variables, mathematical models are built using Nonlinear Programming Method (NLP) ensuring the basic limit of displacement and considering rear viscous separation. We develop ship lines optimization procedures with intellectual property rights. Series60 is used as parent ship in optimization design to obtain improved ship (Series60-1) theoretically. Then drag tests for the improved ship (Series60-1) is made to get the actual minimum total resistance hull form.

Electron affinity of perhalogenated benzenes: A theoretical DFT study

NASA Astrophysics Data System (ADS)

Volatron, François; Roche, Cécile

2007-10-01

The potential energy surfaces (PES) of unsubstituted and perhalogenated benzene anions ( CX6-, X = F, Cl, Br, and I) were explored by means of DFT-B3LYP calculations. In the F and Cl cases seven extrema were located and characterized. In the Br and I cases only one minimum and two extrema were found. In each case the minimum was recomputed at the CCSD(T) level. The electron affinities of C 6X 6 were calculated (ZPE included). The results obtained agree well with the experimental determinations when available. The values obtained in the X = Br and the X = I cases are expected to be valuable predictions.

A generalized force-modified potential energy surface (G-FMPES) for mechanochemical simulations

DOE PAGES

Subramanian, Gopinath; Mathew, Nithin; Leiding, Jeffery A.

2015-10-05

We describe the modifications that a spatially varying external load produces on a Born-Oppenheimer potential energy surface (PES) by calculating static quantities of interest. The effects of the external loads are exemplified using electronic structure calculations (at the HF/6-31G** level) of two different molecules: ethane and hexahydro-1,3,5-trinitro-s-triazine (RDX). The calculated transition states and The Hessian matrices of stationary points show that spatially varying external loads shift the stationary points and modify the curvature of the PES, thereby affecting the harmonic transition rates by altering both the energy barrier as well as the prefactor. The harmonic spectra of both molecules aremore » blue-shifted with increasing compressive “pressure.” Some stationary points on the RDX-PES disappear under application of the external load, indicating the merging of an energy minimum with a saddle point.« less

Controlling hazardous energy sources (lockout/tagout)

NASA Technical Reports Server (NTRS)

Dominguez, Manuel B.

1991-01-01

The minimum requirements as established by the Occupational Safety and Health Administration (OSHA) standard 29 CFR 1910.147 are discussed for preventing the unexpected operation of equipment or release of energy which could cause injury to personnel, damage to equipment, harm to the environment, or loss or compromise of test data. Safety requirements both for government and contractor personnel are explained for potentially hazardous energy sources during work operations at LeRC (Cleveland and Plum Brook Stations). Basic rules are presented to ensure protection against harmful exposures, and baseline implementation requirements are discussed from which detailed lockout/tagout procedures can be developed for individual equipment items. Examples of energy sources covered by this document include electrical, pneumatic, mechanical, chemical, cryogenic, thermal, spring tension/compression suspended or moving loads, and other potentially hazardous sources. Activities covered by this standard include, but are not limited to, construction, maintenance, installation, calibration, inspection, cleaning, or repair.

Controlling hazardous energy sources (lockout/tagout)

NASA Astrophysics Data System (ADS)

Dominguez, Manuel B.

1991-10-01

The minimum requirements as established by the Occupational Safety and Health Administration (OSHA) standard 29 CFR 1910.147 are discussed for preventing the unexpected operation of equipment or release of energy which could cause injury to personnel, damage to equipment, harm to the environment, or loss or compromise of test data. Safety requirements both for government and contractor personnel are explained for potentially hazardous energy sources during work operations at LeRC (Cleveland and Plum Brook Stations). Basic rules are presented to ensure protection against harmful exposures, and baseline implementation requirements are discussed from which detailed lockout/tagout procedures can be developed for individual equipment items. Examples of energy sources covered by this document include electrical, pneumatic, mechanical, chemical, cryogenic, thermal, spring tension/compression suspended or moving loads, and other potentially hazardous sources. Activities covered by this standard include, but are not limited to, construction, maintenance, installation, calibration, inspection, cleaning, or repair.

Path Integral Metadynamics.

PubMed

Quhe, Ruge; Nava, Marco; Tiwary, Pratyush; Parrinello, Michele

2015-04-14

We develop a new efficient approach for the simulation of static properties of quantum systems using path integral molecular dynamics in combination with metadynamics. We use the isomorphism between a quantum system and a classical one in which a quantum particle is mapped into a ring polymer. A history dependent biasing potential is built as a function of the elastic energy of the isomorphic polymer. This enhances fluctuations in the shape and size of the necklace in a controllable manner and allows escaping deep energy minima in a limited computer time. In this way, we are able to sample high free energy regions and cross barriers, which would otherwise be insurmountable with unbiased methods. This substantially improves the ability of finding the global free energy minimum as well as exploring other metastable states. The performance of the new technique is demonstrated by illustrative applications on model potentials of varying complexity.

Helical coil buckling mechanism for a stiff nanowire on an elastomeric substrate

NASA Astrophysics Data System (ADS)

Chen, Youlong; Liu, Yilun; Yan, Yuan; Zhu, Yong; Chen, Xi

2016-10-01

When a stiff nanowire is deposited on a compliant soft substrate, it may buckle into a helical coil form when the system is compressed. Using theoretical and finite element method (FEM) analyses, the detailed three-dimensional coil buckling mechanism for a silicon nanowire (SiNW) on a polydimethylsiloxane (PDMS) substrate is studied. A continuum mechanics approach based on the minimization of the strain energy in the SiNW and elastomeric substrate is developed. Due to the helical buckling, the bending strain in SiNW is significantly reduced and the maximum local strain is almost uniformly distributed along SiNW. Based on the theoretical model, the energy landscape for different buckling modes of SiNW on PDMS substrate is given, which shows that both the in-plane and out-of-plane buckling modes have the local minimum potential energy, whereas the helical buckling model has the global minimum potential energy. Furthermore, the helical buckling spacing and amplitudes are deduced, taking into account the influences of the elastic properties and dimensions of SiNWs. These features are verified by systematic FEM simulations and parallel experiments. As the effective compressive strain in elastomeric substrate increases, the buckling profile evolves from a vertical ellipse to a lateral ellipse, and then approaches to a circle when the effective compressive strain is larger than 30%. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and 3D complex nano-structures.

Stretching of short monatomic gold chains-some model calculations

NASA Astrophysics Data System (ADS)

Sumali, Priyanka, Verma, Veena; Dharamvir, Keya

2012-06-01

The Mechanical properties of zig-zag monatomic gold chains containing 5 and 7 atoms were studied using the Siesta Code (SC), which works within the framework of DFT formalism and Gupta Potential (GP), which is an effective atom-atom potential. The zig-zag chains were stretched by keeping the end atoms fixed while rest of the atoms were relaxed till minimum energy is obtained. Energy, Force and Young's Modulus found using GP and SC were plotted as functions of total length. It is found that the breaking force in case of GP is of order of 1.6nN while for SIESTA is of the order of 2.9nN for both the chains.

Energy deposition by heavy ions: Additivity of kinetic and potential energy contributions in hillock formation on CaF2

PubMed Central

Wang, Y. Y.; Grygiel, C.; Dufour, C.; Sun, J. R.; Wang, Z. G.; Zhao, Y. T.; Xiao, G. Q.; Cheng, R.; Zhou, X. M.; Ren, J. R.; Liu, S. D.; Lei, Y.; Sun, Y. B.; Ritter, R.; Gruber, E.; Cassimi, A.; Monnet, I.; Bouffard, S.; Aumayr, F.; Toulemonde, M.

2014-01-01

Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe22+ to Xe30+) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface. PMID:25034006

Energy deposition by heavy ions: additivity of kinetic and potential energy contributions in hillock formation on CaF2.

PubMed

Wang, Y Y; Grygiel, C; Dufour, C; Sun, J R; Wang, Z G; Zhao, Y T; Xiao, G Q; Cheng, R; Zhou, X M; Ren, J R; Liu, S D; Lei, Y; Sun, Y B; Ritter, R; Gruber, E; Cassimi, A; Monnet, I; Bouffard, S; Aumayr, F; Toulemonde, M

2014-07-18

Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe(22+) to Xe(30+)) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface.

Advances in Household Appliances- A Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, Pradeep; Vineyard, Edward Allan; Abdelaziz, Omar

2011-01-01

An overview of options and potential barriers and risks for reducing the energy consumption, peak demand, and emissions for seven key energy consuming residential products (refrigerator-freezers, dishwashers, clothes washers, clothes dryers, electric ovens, gas ovens and microwave ovens) is presented. The paper primarily concentrates on the potential energy savings from the use of advanced technologies in appliances for the U.S. market. The significance and usefulness of each technology was evaluated in order to prioritize the R&D needs to improve energy efficiency of appliances in view of energy savings, cost, and complexity. The paper provides a snapshot of the future R&Dmore » needs for each of the technologies along with the associated barriers. Although significant energy savings may be achieved, one of the major barriers in most cases is high first cost. One way of addressing this issue and promoting the introduction of new technologies is to level the playing field for all manufacturers by establishing Minimum Energy Performance Standards (MEPS) which are not cost prohibitive and promoting energy efficient products through incentives to both manufacturers and consumers.« less

Appropriateness in using LANDSAT in development energy related data bases

NASA Technical Reports Server (NTRS)

Harnden, E.

1981-01-01

The use of automated classification systems in the field of resource management and resource inventory is discussed. Applications of LANDSAT classification are outlined and include: energy load forecasting based upon land use inventories and change analysis, impact analysis of activities related to energy extraction, capability/suitability mapping in support of generation and substation location and transmission line routing, and assessment of solar energy potential in a highly urbanized setting where land values are high. It is found that the use of LANDSAT data is adequate for general inventories where few data categories are required, where resolution of data to around 150 acres minimum is required, and where no other complete imagery set can be obtained.

High level theoretical study of benzene-halide adducts: the importance of C-H-anion hydrogen bonding.

PubMed

Coletti, Cecilia; Re, Nazzareno

2009-02-26

High level ab initio calculations were performed on the interaction of halide anions (F(-), Cl(-), Br(-), and I(-)) to benzene. For these systems recent experimental and theoretical data are rather scarce, in spite of their growingly acknowledged importance for binding in complex biological systems. We have thus explored the complete basis set limit and the effect of counterpoise basis set superposition error corrections on the minimum geometries and energies of benzene-halide adducts in their possible interaction modes. The binding energy and enthalpy values (ranging from -15.3 kcal/mol for fluoride to -6.1 kcal/mol for iodide) show that the hydrogen bonding occurring in these complexes cannot be described as a weak interaction. We have furthermore investigated the topology of the minima and of other selected sections of the potential energy surface, so to gain further insight on the nature of the halide-benzene interaction. In particular, the geometry corresponding to the C(6v) symmetry, although being overall repulsive, has displayed the unprecedented presence of a small flex (a minimum in C(6v) symmetry) with interaction energy close to zero or slightly attractive.

Surface engineering of zirconium particles by molecular layer deposition: Significantly enhanced electrostatic safety at minimum loss of the energy density

NASA Astrophysics Data System (ADS)

Qin, Lijun; Yan, Ning; Hao, Haixia; An, Ting; Zhao, Fengqi; Feng, Hao

2018-04-01

Because of its high volumetric heat of oxidation, Zr powder is a promising high energy fuel/additive for rocket propellants. However, the application of Zr powder is restricted by its ultra-high electrostatic discharge sensitivity, which poses great hazards for handling, transportation and utilization of this material. By performing molecular layer deposition of polyimide using 1,2,4,5-benzenetetracarboxylic anhydride and ethylenediamine as the precursors, Zr particles can be uniformly encapsulated by thin layers of the polymer. The thicknesses of the encapsulation layers can be precisely controlled by adjusting the number of deposition cycle. High temperature annealing converts the polymer layer into a carbon coating. Results of thermal analyses reveal that the polymer or carbon coatings have little negative effect on the energy release process of the Zr powder. By varying the thickness of the polyimide or carbon coating, electrostatic discharge sensitivity of the Zr powder can be tuned in a wide range and its uncontrolled ignition hazard can be virtually eliminated. This research demonstrates the great potential of molecular layer deposition in effectively modifying the surface properties of highly reactive metal based energetic materials with minimum sacrifices of their energy densities.

Kinetic Energy Transfer Process in a Double Shell Leading to Robust Burn

NASA Astrophysics Data System (ADS)

Montgomery, D. S.; Daughton, W. S.; Albright, B. J.; Wilson, D. C.; Loomis, E. N.; Merritt, E. C.; Dodd, E. S.; Kirkpatrick, R. C.; Watt, R. G.; Rosen, M. D.

2017-10-01

A goal of double shell capsule implosions is to impart sufficient internal energy to the D-T fuel at stagnation in order to obtain robust α-heating and burn with low hot spot convergence, C.R. < 10. A simple description of the kinetic energy transfer from the outer shell to the inner shell is found using shock physics and adiabatic compression, and compares well with 1D modeling. An isobaric model for the stagnation phase of the inner shell is used to determine the ideal partition of internal energy in the D-T fuel. Robust burn of the fuel requires, at minimum, that α-heating exceeds the rate of cooling by expansion of the hot spot so that the yield occurs before the hot spot disassembles, which is then used to define a minimum requirement for robust burn. One potential advantage of a double shell capsule compared to single shell capsules is the use of a heavy metal pusher, which may lead to a longer hot spot disassembly time. We present these analytic results and compare them to 1D and 2D radiation-hydrodynamic simulations. Work performed under the auspices of DOE by LANL under contract DE-AC52-06NA25396.

Potential energy surface and quantum dynamics study of rovibrational states for HO(3) (X (2)A'').

PubMed

Braams, Bastiaan J; Yu, Hua-Gen

2008-06-07

An analytic potential energy surface has been constructed by fitting to about 28 thousand energy points for the electronic ground-state (X (2)A'') of HO(3). The energy points are calculated using a hybrid density functional HCTH and a large basis set aug-cc-pVTZ, i.e., a HCTH/aug-cc-pVTZ density functional theory (DFT) method. The DFT calculations show that the trans-HO(3) isomer is the global minimum with a potential well depth of 9.94 kcal mol(-1) with respect to the OH + O(2) asymptote. The equilibrium geometry of the cis-HO(3) conformer is located 1.08 kcal mol(-1) above that of the trans-HO(3) one with an isomerization barrier of 2.41 kcal mol(-1) from trans- to cis-HO(3). By using this surface, a rigorous quantum dynamics (QD) study has been carried out for computing the rovibrational energy levels of HO(3). The calculated results determine a dissociation energy of 6.15 kcal mol(-1), which is in excellent agreement with the experimental value of Lester et al. [J. Phys. Chem. A, 2007, 111, 4727.].

Estimating Renewable Energy Economic Potential in the United States. Methodology and Initial Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Austin; Beiter, Philipp; Heimiller, Donna

This report describes a geospatial analysis method to estimate the economic potential of several renewable resources available for electricity generation in the United States. Economic potential, one measure of renewable generation potential, may be defined in several ways. For example, one definition might be expected revenues (based on local market prices) minus generation costs, considered over the expected lifetime of the generation asset. Another definition might be generation costs relative to a benchmark (e.g., a natural gas combined cycle plant) using assumptions of fuel prices, capital cost, and plant efficiency. Economic potential in this report is defined as the subsetmore » of the available resource technical potential where the cost required to generate the electricity (which determines the minimum revenue requirements for development of the resource) is below the revenue available in terms of displaced energy and displaced capacity. The assessment is conducted at a high geospatial resolution (more than 150,000 technology-specific sites in the continental United States) to capture the significant variation in local resource, costs, and revenue potential. This metric can be a useful screening factor for understanding the economic viability of renewable generation technologies at a specific location. In contrast to many common estimates of renewable energy potential, economic potential does not consider market dynamics, customer demand, or most policy drivers that may incent renewable energy generation.« less

Nonlinear Schrödinger equations with single power nonlinearity and harmonic potential

NASA Astrophysics Data System (ADS)

Cipolatti, R.; de Macedo Lira, Y.; Trallero-Giner, C.

2018-03-01

We consider a generalized nonlinear Schrödinger equation (GNLS) with a single power nonlinearity of the form λ ≤ft\\vert \\varphi \\right\\vert p , with p  >  0 and λ\\in{R} , in the presence of a harmonic confinement. We report the conditions that p and λ must fulfill for the existence and uniqueness of ground states of the GNLS. We discuss the Cauchy problem and summarize which conditions are required for the nonlinear term λ ≤ft\\vert \\varphi \\right\\vert p to render the ground state solutions orbitally stable. Based on a new variational method we provide exact formulæ for the minimum energy for each index p and the changing range of values of the nonlinear parameter λ. Also, we report an approximate close analytical expression for the ground state energy, performing a comparative analysis of the present variational calculations with those obtained by a generalized Thomas-Fermi approach, and soliton solutions for the respective ranges of p and λ where these solutions can be implemented to describe the minimum energy.

Using a Family of Dividing Surfaces Normal to the Minimum EnergyPath for Quantum Instanton Rate Constants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yimin; Miller, Wlliam H.

2006-02-22

One of the outstanding issues in the quantum instanton (QI) theory (or any transition state-type theory) for thermal rate constants of chemical reactions is the choice of an appropriate ''dividing surface'' (DS) that separates reactants and products. (In the general version of the QI theory, there are actually two dividing surfaces involved.) This paper shows one simple and general way for choosing DS's for use in QI Theory, namely using the family of (hyper) planes normal to the minimum energy path (MEP) on the potential energy surface at various distances s along it. Here the reaction coordinate is not onemore » of the dynamical coordinates of the system (which will in general be the Cartesian coordinates of the atoms), but rather simply a parameter which specifies the DS. It is also shown how this idea can be implemented for an N-atom system in 3d space in a way that preserves overall translational and rotational invariance. Numerical application to a simple system (the colliner H + H{sub 2} reaction) is presented to illustrate the procedure.« less

Universal fingerprinting chip server.

PubMed

Casique-Almazán, Janet; Larios-Serrato, Violeta; Olguín-Ruíz, Gabriela Edith; Sánchez-Vallejo, Carlos Javier; Maldonado-Rodríguez, Rogelio; Méndez-Tenorio, Alfonso

2012-01-01

The Virtual Hybridization approach predicts the most probable hybridization sites across a target nucleic acid of known sequence, including both perfect and mismatched pairings. Potential hybridization sites, having a user-defined minimum number of bases that are paired with the oligonucleotide probe, are first identified. Then free energy values are evaluated for each potential hybridization site, and if it has a calculated free energy of equal or higher negative value than a user-defined free energy cut-off value, it is considered as a site of high probability of hybridization. The Universal Fingerprinting Chip Applications Server contains the software for visualizing predicted hybridization patterns, which yields a simulated hybridization fingerprint that can be compared with experimentally derived fingerprints or with a virtual fingerprint arising from a different sample. The database is available for free at http://bioinformatica.homelinux.org/UFCVH/

Minimum energy, liquid hydrogen supersonic cruise vehicle study

NASA Technical Reports Server (NTRS)

Brewer, G. D.; Morris, R. E.

1975-01-01

The potential was examined of hydrogen-fueled supersonic vehicles designed for cruise at Mach 2.7 and at Mach 2.2. The aerodynamic, weight, and propulsion characteristics of a previously established design of a LH2 fueled, Mach 2.7 supersonic cruise vehicle (SCV) were critically reviewed and updated. The design of a Mach 2.2 SCV was established on a corresponding basis. These baseline designs were then studied to determine the potential of minimizing energy expenditure in performing their design mission, and to explore the effect of fuel price and noise restriction on their design and operating performance. The baseline designs of LH2 fueled aircraft were than compared with equivalent designs of jet A (conventional hydrocarbon) fueled SCV's. Use of liquid hydrogen for fuel for the subject aircraft provides significant advantages in performance, cost, noise, pollution, sonic boom, and energy utilization.

On the potential of Cherenkov Telescope Arrays and KM3 Neutrino Telescopes for the detection of extended sources

NASA Astrophysics Data System (ADS)

Ambrogi, L.; Celli, S.; Aharonian, F.

2018-07-01

We discuss the discovery potential of extended Very-High-Energy (VHE) neutrino sources by the future KM3 Neutrino Telescope (KM3NeT) in the context of the constraining power of the Cherenkov Telescope Array (CTA), designed for deep surveys of the sky in VHE gamma rays. The study is based on a comparative analysis of sensitivities of KM3NeT and CTA. We show that a minimum gamma-ray energy flux of E2ϕγ(10TeV) > 1 ×10-12 TeV cm-2 s-1 is required to identify a possible neutrino counterpart with a 3σ significance and 10 years of KM3NeT observations with upgoing muons, if the source has an angular size of Rsrc = 0 .1∘ and emits gamma rays with an E-2 energy spectrum through a full hadronic mechanism. This minimum gamma-ray flux is increased to the level of E2ϕγ(10TeV) > 2 ×10-11 TeV cm-2 s-1 in case of sources with radial extension of Rsrc = 2 .0∘ . The analysis methods are applied to the supernova remnant RX J1713.7-3946 and the Galactic Center Ridge, as well as to the recent HAWC catalog of multi-TeV gamma-ray sources.

A hybrid optimization algorithm to explore atomic configurations of TiO 2 nanoparticles

DOE PAGES

Inclan, Eric J.; Geohegan, David B.; Yoon, Mina

2017-10-17

Here in this paper we present a hybrid algorithm comprised of differential evolution, coupled with the Broyden–Fletcher–Goldfarb–Shanno quasi-Newton optimization algorithm, for the purpose of identifying a broad range of (meta)stable Ti nO 2n nanoparticles, as an example system, described by Buckingham interatomic potential. The potential and its gradient are modified to be piece-wise continuous to enable use of these continuous-domain, unconstrained algorithms, thereby improving compatibility. To measure computational effectiveness a regression on known structures is used. This approach defines effectiveness as the ability of an algorithm to produce a set of structures whose energy distribution follows the regression as themore » number of Ti nO 2n increases such that the shape of the distribution is consistent with the algorithm’s stated goals. Our calculation demonstrates that the hybrid algorithm finds global minimum configurations more effectively than the differential evolution algorithms, widely employed in the field of materials science. Specifically, the hybrid algorithm is shown to reproduce the global minimum energy structures reported in the literature up to n = 5, and retains good agreement with the regression up to n = 25. For 25 < n < 100, where literature structures are unavailable, the hybrid effectively obtains structures that are in lower energies per TiO 2 unit as the system size increases.« less

Stochastic Formalism for Thermally Driven Distribution Frontier: A Nonempirical Approach to the Potential Escape Problem

NASA Astrophysics Data System (ADS)

Akashi, Ryosuke; Nagornov, Yuri S.

2018-06-01

We develop a non-empirical scheme to search for the minimum-energy escape paths from the minima of the potential surface to unknown saddle points nearby. A stochastic algorithm is constructed to move the walkers up the surface through the potential valleys. This method employs only the local gradient and diagonal part of the Hessian matrix of the potential. An application to a two-dimensional model potential is presented to demonstrate the successful finding of the paths to the saddle points. The present scheme could serve as a starting point toward first-principles simulation of rare events across the potential basins free from empirical collective variables.

Wilson-loop instantons

NASA Technical Reports Server (NTRS)

Lee, Kimyeong; Holman, Richard; Kolb, Edward W.

1987-01-01

Wilson-loop symmetry breaking is considered on a space-time of the form M4 x K, where M4 is a four-dimensional space-time and K is an internal space with nontrivial and finite fundamental group. It is shown in a simple model that the different vacua obtained by breaking a non-Abelian gauge group by Wilson loops are separated in the space of gauge potentials by a finite energy barrier. An interpolating gauge configuration is then constructed between these vacua and shown to have minimum energy. Finally some implications of this construction are discussed.

Trinitromethyl Ethers and Other Derivatives as Superior Oxidizers

DTIC Science & Technology

2011-08-26

well as comparable or superior energy content, so that its performance will be at least equivalent to that of AP. Oxygen balance (relative to CO2) for...21]: 6 C(NO2)4 + M+Cl – → ClC(NO2)3 + M+NO2 – ClC(NO2)3 + LiBr → BrC(NO2)3 + ClC(NO2)2Br BrC(NO2)3 + LiCl → ClC(NO2)3 + LiBr ...hindrance parameter α > 8.87 would not be stable; where Ustrain is the strain energy or the potential energy of the molecule in the minimum position

A Systematic Approach for Computing Zero-Point Energy, Quantum Partition Function, and Tunneling Effect Based on Kleinert's Variational Perturbation Theory.

PubMed

Wong, Kin-Yiu; Gao, Jiali

2008-09-09

In this paper, we describe an automated integration-free path-integral (AIF-PI) method, based on Kleinert's variational perturbation (KP) theory, to treat internuclear quantum-statistical effects in molecular systems. We have developed an analytical method to obtain the centroid potential as a function of the variational parameter in the KP theory, which avoids numerical difficulties in path-integral Monte Carlo or molecular dynamics simulations, especially at the limit of zero-temperature. Consequently, the variational calculations using the KP theory can be efficiently carried out beyond the first order, i.e., the Giachetti-Tognetti-Feynman-Kleinert variational approach, for realistic chemical applications. By making use of the approximation of independent instantaneous normal modes (INM), the AIF-PI method can readily be applied to many-body systems. Previously, we have shown that in the INM approximation, the AIF-PI method is accurate for computing the quantum partition function of a water molecule (3 degrees of freedom) and the quantum correction factor for the collinear H(3) reaction rate (2 degrees of freedom). In this work, the accuracy and properties of the KP theory are further investigated by using the first three order perturbations on an asymmetric double-well potential, the bond vibrations of H(2), HF, and HCl represented by the Morse potential, and a proton-transfer barrier modeled by the Eckart potential. The zero-point energy, quantum partition function, and tunneling factor for these systems have been determined and are found to be in excellent agreement with the exact quantum results. Using our new analytical results at the zero-temperature limit, we show that the minimum value of the computed centroid potential in the KP theory is in excellent agreement with the ground state energy (zero-point energy) and the position of the centroid potential minimum is the expectation value of particle position in wave mechanics. The fast convergent property of the KP theory is further examined in comparison with results from the traditional Rayleigh-Ritz variational approach and Rayleigh-Schrödinger perturbation theory in wave mechanics. The present method can be used for thermodynamic and quantum dynamic calculations, including to systematically determine the exact value of zero-point energy and to study kinetic isotope effects for chemical reactions in solution and in enzymes.

Local-spin-density calculations for iron: Effect of spin interpolation on ground-state properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacLaren, J.M.; Clougherty, D.P.; Albers, R.C.

1990-08-15

Scalar-relativistic self-consistent linear muffin-tin orbital (LMTO) calculations for bcc and fcc Fe have been performed with several different local approximations to the exchange and correlation energy density and potential. Overall, in contrast to the conclusions of previous studies, we find that the local-spin-density approximation to exchange and correlation can provide an adequate description of bulk Fe {ital provided} that a proper parametrization of the correlation energy density and potential of the homogeneous electron gas over both spin and density is used. Lattice constants, found from the position of the minimum of the total energy as a function of Wigner-Seitz radius,more » agree to within 1% (for {ital s},{ital p},{ital d} LMTO's only) and within 1--2% (for {ital s},{ital p},{ital d},{ital f} LMTO's) of the experimental lattice constants for all forms used for the local correlation. The best agreement, however, was obtained using a local correlation potential derived from the Vosko-Wilk-Nusair form for the spin dependence of the correlation energy density. The calculation performed with this correlation potential was also the only calculation to correctly predict a bcc ferromagnetic ground state.« less

Inherent structures of crystalline pentacene

NASA Astrophysics Data System (ADS)

Della Valle, Raffaele Guido; Venuti, Elisabetta; Brillante, Aldo; Girlando, Alberto

2003-01-01

Using a quasi-Monte Carlo scheme, we search the potential energy surface of crystalline pentacene to sample its local minima, which represent the "inherent" structures, i.e., the possible configurations of mechanical equilibrium. The system is described in terms of rigid molecules interacting through a standard atom-atom potential model. Several hundreds of distinct minima are encountered, with a surprising variety of structural arrangements. We find that deep minima are easily accessible because they exhibit a favorable energy distribution and their attraction basins tend to be wide. Thanks to these features of the potential surface, the localization the global minimum becomes entirely feasible, allowing reliable a priori predictions of the crystallographic structures. The results for pentacene are very satisfactory. In fact, the two deepest minima correspond to the structures of the two known experimental polymorphs, which are described correctly. Further polymorphs are also likely to exist.

Ascent trajectory optimization for stratospheric airship with thermal effects

NASA Astrophysics Data System (ADS)

Guo, Xiao; Zhu, Ming

2013-09-01

Ascent trajectory optimization with thermal effects is addressed for a stratospheric airship. Basic thermal characteristics of the stratospheric airship are introduced. Besides, the airship’s equations of motion are constructed by including the factors about aerodynamic force, added mass and wind profiles which are developed based on horizontal-wind model. For both minimum-time and minimum-energy flights during ascent, the trajectory optimization problem is described with the path and terminal constraints in different scenarios and then, is converted into a parameter optimization problem by a direct collocation method. Sparse Nonlinear OPTimizer(SNOPT) is employed as a nonlinear programming solver and two scenarios are adopted. The solutions obtained illustrate that the trajectories are greatly affected by the thermal behaviors which prolong the daytime minimum-time flights of about 20.8% compared with that of nighttime in scenario 1 and of about 10.5% in scenario 2. And there is the same trend for minimum-energy flights. For the energy consumption of minimum-time flights, 6% decrease is abstained in scenario 1 and 5% decrease in scenario 2. However, a few energy consumption reduction is achieved for minimum-energy flights. Solar radiation is the principal component and the natural wind also affects the thermal behaviors of stratospheric airship during ascent. The relationship between take-off time and performance of airship during ascent is discussed. it is found that the take-off time at dusk is best choice for stratospheric airship. And in addition, for saving energy, airship prefers to fly downwind.

Vibrational spectroscopic and structural investigations on fullerene: A DFT approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christy, P. Anto; Premkumar, S.; Asath, R. Mohamed

2016-05-06

The molecular structure of fullerene (C{sub 60}) molecule was optimized by the DFT/B3LYP method with 6-31G and 6-31G(d,p) basis sets using Gaussian 09 program. The vibrational frequencies were calculated for the optimized molecular structure of the molecule. The calculated vibrational frequencies confirm that the molecular structure of the molecule was located at the minimum energy potential energy surface. The calculated vibrational frequencies were assigned on the basis of functional group analysis and also confirmed using the GaussView 05 software. The frontier molecular orbitals analysis was carried out. The FMOs related molecular properties were predicted. The higher ionization potential, higher electronmore » affinity, higher softness, lower band gap energy and lower hardness values were obtained, which confirm that the fullerene molecule has a higher molecular reactivity. The Mulliken atomic charge distribution of the molecule was also calculated. Hence, these results play an important role due to its potential applications as drug delivery devices.« less

Theoretical investigation on the potential energy surface for the reactions of B, Al and Ga with NO

NASA Astrophysics Data System (ADS)

Zhang, Luning; Zhou, Mingfei

2000-06-01

The structures, binding energies and vibrational frequencies of various MNO structural isomers (M=B, Al and Ga) in their ground triplet states have been determined using the density functional (B3LYP, BP86 and B3PW91) and MP2 methods. The potential energy surfaces of the M+NO reactions have been developed at the B3LYP/6-311+G(d) level of theory, and transition states on the isomerization potential energy surfaces have been characterized. Our calculation results show that four BNO isomers, namely, nitrosyl BNO, isonitrosyl BON, side-bonded B- η2-NO and the inserted NBO molecules are stationary points, while for Al and Ga, only the MNO (nitrosyl), MON (isonitrosyl) and the OMN (insertion) molecules are local minimum. The B+NO reaction products are more strongly bonded compared to the Al and Ga+NO systems due to strong covalent bonding. The interactions of B, Al and Ga atoms with NO to generate nitrosyl and isonitrosyl addition molecules are barrierless, but subsequent isomerization reactions to form the side-bonded molecules and the inserted products require activation energy.

Potential energy surfaces related to the ion-molecule reaction C/sup +/ + H/sub 2/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liskow, D.H.; Bender, C.F.; Schaefer, H.F. III

1974-10-01

The C/sup +/ + H/sub 2/ ion-molecule reaction has been studied by several experimental groups and appears likely to become the focal point of much experimental and theoretical activity. Ab initio self-consistent-field and configuration interaction calculations have accordingly been carried out for this system. A double zeta basis set of contracted Gaussian functions was employed and as many as 648 configurations included. For isosceles triangle configurations (C/sub 2V/ point group) the /sup 2/A/sub 1/, /sup 2/B/sub 1/, and /sup 2/B/sub 2/ potential surfaces were considered, while for linear geometries (C/sub infinity V) the /sup 2/..sigma../sup +/ and /sup 2/PI surfacesmore » were studied. For general (C/sub S/) geometry, the lowest /sup 2/A' potential surface was considered. Properties reported include minimum energy paths and energy profiles for the various processes considered. The intuitive correlation diagram of Mahan and Sloane is given qualitative reliability. Pathways to CH/sub 2//sup +/ complex formation are shown to depend crucially on the C/sub S/ potential surface.« less

Polarization effects in low-energy electron-CH4 elastic collisions in an exact exchange treatment

NASA Astrophysics Data System (ADS)

Jain, Ashok; Weatherford, C. A.; Thompson, D. G.; McNaughten, P.

1989-12-01

We have investigated the polarization effects in very-low-energy (below 1 eV) electron- CH4 collisions in an exact-exchange treatment. The two models of the parameter-free polarization potential are employed; one, the VpolJT potential, introduced by Jain and Thompson [J. Phys. B 15, L631 (1982)], is based on an approximate polarized-orbital method, and two, the correlation-polarization potential VpolCP, first proposed by O'Connel and Lane [Phys. Rev. A 27, 1893 (1983)], is given as a simple analytic form in terms of the charge density of the target. In this rather very low-energy region, the polarization effects play a decisive role, particularly in creating structure in the differential cross section (DCS) and producing the Ramsauer-Townsend minimum in the total cross section. Our DCS at 0.2, 0.4, and 0.6 eV are compared with recent measurements. We found that a local parameter-free approximation for the polarization potential is quite successful if it is determined under the polarized-orbital-type technique rather than based on the correlation-polarization approach.

Ferromagnetic core valve gives rapid action on minimum energy

NASA Technical Reports Server (NTRS)

Larson, A. V.; Tinkham, J. P.

1967-01-01

Miniature solenoid valve controls propellant flow during tests on a coaxial plasma accelerator. It uses an advanced ferromagnetic core design which meets all the rapid-acting requirements with a minimum of input energy.

Power Factor Controller

NASA Technical Reports Server (NTRS)

1997-01-01

Frank Nola invented the Power Factor Controller (PFC) at Marshall Space Flight Center more than a decade ago. Nola came up with a way to curb power wastage in AC induction motors. The PFC matches voltage with the motor's actual need by continuously sensing shifts between voltage and current. When it senses a light load it cuts the voltage to the minimum needed. Potential energy savings range from 8 to 65 percent.

Benefit from NASA

NASA Image and Video Library

1997-01-01

Frank Nola invented the Power Factor Controller (PFC) at Marshall Space Flight Center more than a decade ago. Nola came up with a way to curb power wastage in AC induction motors. The PFC matches voltage with the motor's actual need by continuously sensing shifts between voltage and current. When it senses a light load it cuts the voltage to the minimum needed. Potential energy savings range from 8 to 65 percent.

High-Level ab initio electronic structure calculations of Water Clusters (H2O)16 and (H2O)17: a new global minimum for (H2O)16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Soohaeng; Apra, Edoardo; Zeng, Xiao Cheng

The lowest-energy structures of water clusters (H2O)16 and (H2O)17 were revisited at the MP2 and CCSD(T) levels of theory. A new global minimum structure for (H2O)16 was found at the MP2 and CCSD(T) levels of theory and the effect of zero-point energy corrections on the relative stability of the low-lying minimum energy structures was assessed. For (H2O)17 the CCSD(T) calculations confirm the previously found at the MP2 level of theory "interior" arrangement (fully coordinated water molecule inside a spherical cluster) as the global minimum.

High-Level ab-initio Electronic Structure Calculations of Water Clusters (H2O)16 and (H2O)17 : a New Global Minimum for (H2O)16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Soohaeng; Apra, Edoardo; Zeng, X.C.

The lowest-energy structures of water clusters (H2O)16 and (H2O)17 were revisited at the MP2 and CCSD(T) levels of theory. A new global minimum structure for (H2O)16 was found at both the MP2 and CCSD(T) levels of theory, and the effect of zero-point energy corrections on the relative stability of the low-lying minimum energy structures was assessed. For (H2O)17, the CCSD(T) calculations confirm the previously found at the MP2 level of theory interior arrangement (fully coordinated water molecule inside a spherical cluster) as the global minimum

Theoretical survey of the reaction between osmium and acetaldehyde

NASA Astrophysics Data System (ADS)

Dai, Guo-Liang; Wang, Chuan-Feng

2012-05-01

The mechanism of the reaction of osmium atom with acetaldehyde has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ sdd/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, C-O, and methyl C-H activation. These reactions can lead to four different products (HOsCH3 + CO, OsCO + CH4, OsCOCH3 + H, and OsO + C2H4). The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. This potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Understanding Gauss’s law using spreadsheets

NASA Astrophysics Data System (ADS)

Baird, William H.

2013-09-01

Some of the results from the electrostatics portion of introductory physics are particularly difficult for students to understand and/or believe. For students who have yet to take vector calculus, Gauss’s law is far from obvious and may seem more difficult than Coulomb’s. When these same students are told that the minimum potential energy for charges added to a conductor is realized when all charges are on the surface, they may have a hard time believing that the energy would not be lowered if just one of those charges were moved from the surface to the interior of a conductor. Investigating these ideas using Coulomb’s law and/or the formula for the potential energy of a system of discrete charges might be tempting, but as the number of charges climbs past a few the calculations become tedious. A spreadsheet enables students to perform these for a hundred or more charges and confirm the familiar results.

Broad-Band Pump-Probe Spectroscopy Quantifies Ultrafast Solvation Dynamics of Proteins and Molecules.

PubMed

Jumper, Chanelle C; Arpin, Paul C; Turner, Daniel B; McClure, Scott D; Rafiq, Shahnawaz; Dean, Jacob C; Cina, Jeffrey A; Kovac, Philip A; Mirkovic, Tihana; Scholes, Gregory D

2016-11-17

In this work, we demonstrate the use of broad-band pump-probe spectroscopy to measure femtosecond solvation dynamics. We report studies of a rhodamine dye in methanol and cryptophyte algae light-harvesting proteins in aqueous suspension. Broad-band impulsive excitation generates a vibrational wavepacket that oscillates on the excited-state potential energy surface, destructively interfering with itself at the minimum of the surface. This destructive interference gives rise to a node at a certain probe wavelength that varies with time. This reveals the Gibbs free-energy changes of the excited-state potential energy surface, which equates to the solvation time correlation function. This method captures the inertial solvent response of water (∼40 fs) and the bimodal inertial response of methanol (∼40 and ∼150 fs) and reveals how protein-buried chromophores are sensitive to the solvent dynamics inside and outside of the protein environment.

Study of thermodynamic properties of liquid binary alloys by a pseudopotential method

NASA Astrophysics Data System (ADS)

Vora, Aditya M.

2010-11-01

On the basis of the Percus-Yevick hard-sphere model as a reference system and the Gibbs-Bogoliubov inequality, a thermodynamic perturbation method is applied with the use of the well-known model potential. By applying a variational method, the hard-core diameters are found which correspond to a minimum free energy. With this procedure, the thermodynamic properties such as the internal energy, entropy, Helmholtz free energy, entropy of mixing, and heat of mixing are computed for liquid NaK binary systems. The influence of the local-field correction functions of Hartree, Taylor, Ichimaru-Utsumi, Farid-Heine-Engel-Robertson, and Sarkar-Sen-Haldar-Roy is also investigated. The computed excess entropy is in agreement with available experimental data in the case of liquid alloys, whereas the agreement for the heat of mixing is poor. This may be due to the sensitivity of the latter to the potential parameters and dielectric function.

Resonance of relativistic electrons with electromagnetic ion cyclotron waves

DOE PAGES

Denton, R. E.; Jordanova, V. K.; Bortnik, J.

2015-06-29

Relativistic electrons have been thought to more easily resonate with electromagnetic ion cyclotron EMIC waves if the total density is large. We show that, for a particular EMIC mode, this dependence is weak due to the dependence of the wave frequency and wave vector on the density. A significant increase in relativistic electron minimum resonant energy might occur for the H band EMIC mode only for small density, but no changes in parameters significantly decrease the minimum resonant energy from a nominal value. The minimum resonant energy depends most strongly on the thermal velocity associated with the field line motionmore » of the hot ring current protons that drive the instability. High density due to a plasmasphere or plasmaspheric plume could possibly lead to lower minimum resonance energy by causing the He band EMIC mode to be dominant. We demonstrate these points using parameters from a ring current simulation.« less

Heteroaromatic π-Stacking Energy Landscapes

PubMed Central

2014-01-01

In this study we investigate π-stacking interactions of a variety of aromatic heterocycles with benzene using dispersion corrected density functional theory. We calculate extensive potential energy surfaces for parallel-displaced interaction geometries. We find that dispersion contributes significantly to the interaction energy and is complemented by a varying degree of electrostatic interactions. We identify geometric preferences and minimum interaction energies for a set of 13 5- and 6-membered aromatic heterocycles frequently encountered in small drug-like molecules. We demonstrate that the electrostatic properties of these systems are a key determinant for their orientational preferences. The results of this study can be applied in lead optimization for the improvement of stacking interactions, as it provides detailed energy landscapes for a wide range of coplanar heteroaromatic geometries. These energy landscapes can serve as a guide for ring replacement in structure-based drug design. PMID:24773380

Refractive effects and Airy structure in inelastic 16O+12C rainbow scattering

NASA Astrophysics Data System (ADS)

Ohkubo, S.; Hirabayashi, Y.; Ogloblin, A. A.; Gloukhov, Yu. A.; Dem'yanova, A. S.; Trzaska, W. H.

2014-12-01

Inelastic 16O+12C rainbow scattering to the 2+ (4.44 MeV) state of 12C was measured at the incident energies, EL = 170, 181, 200, 260, and 281 MeV. A systematic analysis of the experimental angular distributions was performed using the coupled-channels method with an extended double folding potential derived from realistic wave functions for 12C and 16O calculated with a microscopic α cluster model and a finite-range density-dependent nucleon-nucleon force. The coupled-channels analysis of the measured inelastic-scattering data shows consistently some Airy-like structure in the inelastic-scattering cross sections for the first 2+ state of 12C, which is somewhat obscured and still not clearly visible in the measured data. The Airy minimum was identified from the analysis and the systematic energy evolution of the Airy structure was studied. The Airy minimum in inelastic scattering is found to be shifted backward compared with that in elastic scattering.

Characterization of the Minimum Energy Path for the Reaction of Singlet Methylene with N2: The Role of Singlet Methylene in Prompt NO

NASA Technical Reports Server (NTRS)

Walch, Stephen P.

1995-01-01

We report calculations of the minimum energy pathways connecting (1)CH2+N2 to diazomethane and diazirine, for the rearrangement of diazirine to diazomethane, for the dissociation of diazirine to HCN2+H, and of diazomethane to CH2N+N. The calculations use complete active space self-consistent field (CASSCF) derivative methods to characterize the stationary points and internally contracted configuration interaction (ICCI) to determine the energetics. The calculations suggest a potential new source of prompt NO from the reaction of (1)CH2 with N2 to give diazirine, and subsequent reaction of diazirine with hydrogen abstracters to form doublet HCN2, which leads to HCN+N(S-4) on the previously studied CH+N2 Surface. The calculations also predict accurate 0 K heats of formation of 77.7 kcal/mol and 68.0 kcal/mol for diazirine and diazomethane, respectively.

Improved Potential Energy Surface of Ozone Constructed Using the Fitting by Permutationally Invariant Polynomial Function

DOE PAGES

Ayouz, Mehdi; Babikov, Dmitri

2012-01-01

New global potential energy surface for the ground electronic state of ozone is constructed at the complete basis set level of the multireference configuration interaction theory. A method of fitting the data points by analytical permutationally invariant polynomial function is adopted. A small set of 500 points is preoptimized using the old surface of ozone. In this procedure the positions of points in the configuration space are chosen such that the RMS deviation of the fit is minimized. New ab initio calculations are carried out at these points and are used to build new surface. Additional points are added tomore » the vicinity of the minimum energy path in order to improve accuracy of the fit, particularly in the region where the surface of ozone exhibits a shallow van der Waals well. New surface can be used to study formation of ozone at thermal energies and its spectroscopy near the dissociation threshold.« less

SU-E-T-489: Quantum versus Classical Trajectory Monte Carlo Simulations of Low Energy Electron Transport.

PubMed

Thomson, R; Kawrakow, I

2012-06-01

Widely-used classical trajectory Monte Carlo simulations of low energy electron transport neglect the quantum nature of electrons; however, at sub-1 keV energies quantum effects have the potential to become significant. This work compares quantum and classical simulations within a simplified model of electron transport in water. Electron transport is modeled in water droplets using quantum mechanical (QM) and classical trajectory Monte Carlo (MC) methods. Water droplets are modeled as collections of point scatterers representing water molecules from which electrons may be isotropically scattered. The role of inelastic scattering is investigated by introducing absorption. QM calculations involve numerically solving a system of coupled equations for the electron wavefield incident on each scatterer. A minimum distance between scatterers is introduced to approximate structured water. The average QM water droplet incoherent cross section is compared with the MC cross section; a relative error (RE) on the MC results is computed. RE varies with electron energy, average and minimum distances between scatterers, and scattering amplitude. The mean free path is generally the relevant length scale for estimating RE. The introduction of a minimum distance between scatterers increases RE substantially (factors of 5 to 10), suggesting that the structure of water must be modeled for accurate simulations. Inelastic scattering does not improve agreement between QM and MC simulations: for the same magnitude of elastic scattering, the introduction of inelastic scattering increases RE. Droplet cross sections are sensitive to droplet size and shape; considerable variations in RE are observed with changing droplet size and shape. At sub-1 keV energies, quantum effects may become non-negligible for electron transport in condensed media. Electron transport is strongly affected by the structure of the medium. Inelastic scatter does not improve agreement between QM and MC simulations of low energy electron transport in condensed media. © 2012 American Association of Physicists in Medicine.

Energy Efficiency Appliance Standards: Where do we stand, how far can we go and how do we get there? An analysis across several economies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Letschert, Virginie E.; de la Rue du Can, Stephane; McNeil, Michael A.

This paper analyses several potential savings scenarios for minimum energy performance standard (MEPS) and comparable programs for governments participating i n the Super-efficient Equipment and Appliance Deployment (SEAD) Initiative, of the Clean Energy Ministerial, which represent over 60% of primary energy consumption in the world. We compare projected energy savings from the main end uses in the residential sector using three energy efficiency scenarios: (1) recent achievements, (2) cost-effective saving potential, and (3) energy efficiency technical potential. The recent achievement scenario (1) evaluates the future impact of MEPS enacted or under development between 2010 and 2012. The cost-effective potential scenariomore » (2) identifies the maximum potential for energy efficiency that results in net benefits to the consumer. The best available technology scenario (3) re presents the full potential of energy efficiency considering best available technologies as candidates for MEPS and incentive programs. We use the Bottom Up Energy Analysis System (BUENAS), developed by Lawrence Berkeley National Laboratory in collaboration with the Collaborative Labelling and Appliances Standards Program (CLASP), to provide a consistent methodology to com pare the different scenarios. This paper focuses on the main end uses in the residential sector. The comparison of the three scenarios for each economy provides possible opportunities for scaling up current policies or implementing additional policies. This comparison across economies reveals country best practices as well as end uses that present the greatest additional potential savings. The paper describes areas where methodologies and additional policy instruments can increase penetration of energy efficient technologies. First , we summarize the barriers and provide remedial policy tools/best practices, such as techno-economic analysis, in response to each barriers that prevent economies from capturing the full cost-effective potentials of MEPS (Scenario 1 to 2). Then, we consider the possible complementary policy options, such as incentive pro grams, to reach the full technical potential of energy efficiency in the residential sector (Scenario 2 to 3).« less

On the critical flame radius and minimum ignition energy for spherical flame initiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zheng; Burke, M. P.; Ju, Yiguang

2011-01-01

Spherical flame initiation from an ignition kernel is studied theoretically and numerically using different fuel/oxygen/helium/argon mixtures (fuel: hydrogen, methane, and propane). The emphasis is placed on investigating the critical flame radius controlling spherical flame initiation and its correlation with the minimum ignition energy. It is found that the critical flame radius is different from the flame thickness and the flame ball radius and that their relationship depends strongly on the Lewis number. Three different flame regimes in terms of the Lewis number are observed and a new criterion for the critical flame radius is introduced. For mixtures with Lewis numbermore » larger than a critical Lewis number above unity, the critical flame radius is smaller than the flame ball radius but larger than the flame thickness. As a result, the minimum ignition energy can be substantially over-predicted (under-predicted) based on the flame ball radius (the flame thickness). The results also show that the minimum ignition energy for successful spherical flame initiation is proportional to the cube of the critical flame radius. Furthermore, preferential diffusion of heat and mass (i.e. the Lewis number effect) is found to play an important role in both spherical flame initiation and flame kernel evolution after ignition. It is shown that the critical flame radius and the minimum ignition energy increase significantly with the Lewis number. Therefore, for transportation fuels with large Lewis numbers, blending of small molecule fuels or thermal and catalytic cracking will significantly reduce the minimum ignition energy.« less

Effect of flow velocity and temperature on ignition characteristics in laser ignition of natural gas and air mixtures

NASA Astrophysics Data System (ADS)

Griffiths, J.; Riley, M. J. W.; Borman, A.; Dowding, C.; Kirk, A.; Bickerton, R.

2015-03-01

Laser induced spark ignition offers the potential for greater reliability and consistency in ignition of lean air/fuel mixtures. This increased reliability is essential for the application of gas turbines as primary or secondary reserve energy sources in smart grid systems, enabling the integration of renewable energy sources whose output is prone to fluctuation over time. This work details a study into the effect of flow velocity and temperature on minimum ignition energies in laser-induced spark ignition in an atmospheric combustion test rig, representative of a sub 15 MW industrial gas turbine (Siemens Industrial Turbomachinery Ltd., Lincoln, UK). Determination of minimum ignition energies required for a range of temperatures and flow velocities is essential for establishing an operating window in which laser-induced spark ignition can operate under realistic, engine-like start conditions. Ignition of a natural gas and air mixture at atmospheric pressure was conducted using a laser ignition system utilizing a Q-switched Nd:YAG laser source operating at 532 nm wavelength and 4 ns pulse length. Analysis of the influence of flow velocity and temperature on ignition characteristics is presented in terms of required photon flux density, a useful parameter to consider during the development laser ignition systems.

Muskellunge growth potential in northern Wisconsin: implications for trophy management

USGS Publications Warehouse

Faust, Matthew D.; Isermann, Daniel A.; Luehring, Mark A.; Hansen, Michael J.

2015-01-01

The growth potential of Muskellunge Esox masquinongy was evaluated by back-calculating growth histories from cleithra removed from 305 fish collected during 1995–2011 to determine whether it was consistent with trophy management goals in northern Wisconsin. Female Muskellunge had a larger mean asymptotic length (49.8 in) than did males (43.4 in). Minimum ultimate size of female Muskellunge (45.0 in) equaled the 45.0-in minimum length limit, but was less than the 50.0-in minimum length limit used on Wisconsin's trophy waters, while the minimum ultimate size of male Muskellunge (34.0 in) was less than the statewide minimum length limit. Minimum reproductive sizes for both sexes were less than Wisconsin's trophy minimum length limits. Mean growth potential of female Muskellunge in northern Wisconsin appears to be sufficient for meeting trophy management objectives and angler expectations. Muskellunge in northern Wisconsin had similar growth potential to those in Ontario populations, but lower growth potential than Minnesota's populations, perhaps because of genetic and environmental differences.

Designing adaptive operating rules for a large multi-purpose reservoir

NASA Astrophysics Data System (ADS)

Geressu, Robel; Rougé, Charles; Harou, Julien

2017-04-01

Reservoirs whose live storage capacity is large compared with annual inflow have "memory", i.e., their storage levels contain information about past inflows and reservoir operations. Such "long-memory" reservoirs can be found in basins in dry regions such as the Nile River Basin in Africa, the Colorado River Basin in the US, or river basins in Western and Central Asia. There the effects of a dry year have the potential to impact reservoir levels and downstream releases for several subsequent years, prompting tensions in transboundary basins. Yet, current reservoir operation rules in those reservoirs do not reflect this by integrating past climate history and release decisions among the factors that influence operating decisions. This work proposes and demonstrates an adaptive reservoir operating rule that explicitly accounts for the recent history of release decisions, and not only current storage level and near-term inflow forecasts. This implies adding long-term (e.g., multiyear) objectives to the existing short-term (e.g., annual) ones. We apply these operating rules to the Grand Ethiopian Renaissance Dam, a large reservoir under construction on the Blue Nile River. Energy generation has to be balanced with the imperative of releasing enough water in low flow years (e.g., the minimum 1, 2 or 3 year cumulative flow) to avoid tensions with downstream countries, Sudan and Egypt. Maximizing the minimum multi-year releases could be of interest for the Nile problem to minimize the impact on performance of the large High Aswan Dam in Egypt. Objectives include maximizing the average and minimum annual energy generation and maximizing the minimum annual, two year and three year cumulative releases. The system model is tested using 30 stochastically generated streamflow series. One can then derive adaptive release rules depending on the value of one- and two-year total releases with respect to thresholds. Then, there are 3 sets of release rules for the reservoir depending on whether one or both thresholds are not met, vs. only one with a non-adaptive rule. Multi-objective evolutionary algorithms (MOEAs) are used to obtain the Pareto front, i.e., non-dominated adaptive and non-adaptive operating rule sets. Implementing adaptive rules is found to improve the trade-offs between energy generation criteria and minimum release targets. Compared with non-adaptive operations, an adaptive operating policy shows an increase of around 3 and 10 Billion cubic meters in the minimum 1 and 3-year cumulative releases for a given value of the same average annual energy generation.

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

NASA Astrophysics Data System (ADS)

Zhao, Jie; Lu, Bing-Nan; Vretenar, Dario; Zhao, En-Guang; Zhou, Shan-Gui

2015-01-01

Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226,228,230,232Th and 232,235,236,238U are mapped and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U . The third minima in 230 ,232Th are very shallow, whereas those in 226 ,228Th and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 ,228 ,230Th . Single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z =90 proton energy gap at β20≈1.5 and β30≈0.7 . Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases with increasing neutron number. The origin of the third minimum is due to the proton Z =90 shell gap at relevant deformations.

Direct dynamics simulation of dioxetane formation and decomposition via the singlet .O-O-CH2-CH2. biradical: Non-RRKM dynamics

NASA Astrophysics Data System (ADS)

Sun, Rui; Park, Kyoyeon; de Jong, Wibe A.; Lischka, Hans; Windus, Theresa L.; Hase, William L.

2012-07-01

Electronic structure calculations and direct chemical dynamics simulations are used to study the formation and decomposition of dioxetane on its ground state singlet potential energy surface. The stationary points for 1O2 + C2H4, the singlet .O-O-CH2-CH2. biradical, the transition state (TS) connecting this biradical with dioxetane, and the two transition states and gauche .O-CH2-CH2-O. biradical connecting dioxetane with the formaldehyde product molecules are investigated at different levels of electronic structure theory including UB3LYP, UMP2, MRMP2, and CASSCF and a range of basis sets. The UB3LYP/6-31G* method was found to give representative energies for the reactive system and was used as a model for the simulations. UB3LYP/6-31G* direct dynamics trajectories were initiated at the TS connecting the .O-O-CH2-CH2. biradical and dioxetane by sampling the TS's vibrational energy levels, and rotational and reaction coordinate energies, with Boltzmann distributions at 300, 1000, and 1500 K. This corresponds to the transition state theory model for trajectories that pass the TS. The trajectories were directed randomly towards both the biradical and dioxetane. A small fraction of the trajectories directed towards the biradical recrossed the TS and formed dioxetane. The remainder formed 1O2 + C2H4 and of these ˜ 40% went directly from the TS to 1O2 + C2H4 without getting trapped and forming an intermediate in the .O-O-CH2-CH2. biradical potential energy minimum, a non-statistical result. The dioxetane molecules which are formed dissociate to two formaldehyde molecules with a rate constant two orders of magnitude smaller than that predicted by Rice-Ramsperger-Kassel-Marcus theory. The reaction dynamics from dioxetane to the formaldehyde molecules do not follow the intrinsic reaction coordinate or involve trapping in the gauche .O-CH2-CH2-O. biradical potential energy minimum. Important non-statistical dynamics are exhibited for this reactive system.

Ratio of shear viscosity to entropy density in multifragmentation of Au + Au

NASA Astrophysics Data System (ADS)

Zhou, C. L.; Ma, Y. G.; Fang, D. Q.; Li, S. X.; Zhang, G. Q.

2012-06-01

The ratio of the shear viscosity (η) to entropy density (s) for the intermediate energy heavy-ion collisions has been calculated by using the Green-Kubo method in the framework of the quantum molecular dynamics model. The theoretical curve of η/s as a function of the incident energy for the head-on Au + Au collisions displays that a minimum region of η/s has been approached at higher incident energies, where the minimum η/s value is about 7 times Kovtun-Son-Starinets (KSS) bound (1/4π). We argue that the onset of minimum η/s region at higher incident energies corresponds to the nuclear liquid gas phase transition in nuclear multifragmentation.

Elementary Mechanisms of Shear-Coupled Grain Boundary Migration

NASA Astrophysics Data System (ADS)

Rajabzadeh, A.; Mompiou, F.; Legros, M.; Combe, N.

2013-06-01

A detailed theoretical study of the elementary mechanisms occurring during the shear-coupled grain boundary (GB) migration at low temperature is performed focusing on both the energetic and structural characteristics. The migration of a Σ13(320) GB in a copper bicrystal in response to external shear displacements is simulated using a semiempirical potential. The minimum energy path of the shear-coupled GB migration is computed using the nudge elastic band method. The GB migration occurs through the nucleation and motion of GB steps identified as disconnections. Energy barriers for the GB and disconnection migrations are evaluated.

Techno-Economic Analysis of the Deacetylation and Disk Refining Process. Characterizing the Effect of Refining Energy and Enzyme Usage on Minimum Sugar Selling Price and Minimum Ethanol Selling Price

DOE PAGES

Chen, Xiaowen; Shekiro, Joseph; Pschorn, Thomas; ...

2015-10-29

A novel, highly efficient deacetylation and disk refining (DDR) process to liberate fermentable sugars from biomass was recently developed at the National Renewable Energy Laboratory (NREL). The DDR process consists of a mild, dilute alkaline deacetylation step followed by low-energy-consumption disk refining. The DDR corn stover substrates achieved high process sugar conversion yields, at low to modest enzyme loadings, and also produced high sugar concentration syrups at high initial insoluble solid loadings. The sugar syrups derived from corn stover are highly fermentable due to low concentrations of fermentation inhibitors. The objective of this work is to evaluate the economic feasibilitymore » of the DDR process through a techno-economic analysis (TEA). A large array of experiments designed using a response surface methodology was carried out to investigate the two major cost-driven operational parameters of the novel DDR process: refining energy and enzyme loadings. The boundary conditions for refining energy (128–468 kWh/ODMT), cellulase (Novozyme’s CTec3) loading (11.6–28.4 mg total protein/g of cellulose), and hemicellulase (Novozyme’s HTec3) loading (0–5 mg total protein/g of cellulose) were chosen to cover the most commercially practical operating conditions. The sugar and ethanol yields were modeled with good adequacy, showing a positive linear correlation between those yields and refining energy and enzyme loadings. The ethanol yields ranged from 77 to 89 gallons/ODMT of corn stover. The minimum sugar selling price (MSSP) ranged from $0.191 to $0.212 per lb of 50 % concentrated monomeric sugars, while the minimum ethanol selling price (MESP) ranged from $2.24 to $2.54 per gallon of ethanol. The DDR process concept is evaluated for economic feasibility through TEA. The MSSP and MESP of the DDR process falls within a range similar to that found with the deacetylation/dilute acid pretreatment process modeled in NREL’s 2011 design report. The DDR process is a much simpler process that requires less capital and maintenance costs when compared to conventional chemical pretreatments with pressure vessels. As a result, we feel the DDR process should be considered as an option for future biorefineries with great potential to be more cost-effective.« less

Techno-Economic Analysis of the Deacetylation and Disk Refining Process. Characterizing the Effect of Refining Energy and Enzyme Usage on Minimum Sugar Selling Price and Minimum Ethanol Selling Price

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xiaowen; Shekiro, Joseph; Pschorn, Thomas

A novel, highly efficient deacetylation and disk refining (DDR) process to liberate fermentable sugars from biomass was recently developed at the National Renewable Energy Laboratory (NREL). The DDR process consists of a mild, dilute alkaline deacetylation step followed by low-energy-consumption disk refining. The DDR corn stover substrates achieved high process sugar conversion yields, at low to modest enzyme loadings, and also produced high sugar concentration syrups at high initial insoluble solid loadings. The sugar syrups derived from corn stover are highly fermentable due to low concentrations of fermentation inhibitors. The objective of this work is to evaluate the economic feasibilitymore » of the DDR process through a techno-economic analysis (TEA). A large array of experiments designed using a response surface methodology was carried out to investigate the two major cost-driven operational parameters of the novel DDR process: refining energy and enzyme loadings. The boundary conditions for refining energy (128–468 kWh/ODMT), cellulase (Novozyme’s CTec3) loading (11.6–28.4 mg total protein/g of cellulose), and hemicellulase (Novozyme’s HTec3) loading (0–5 mg total protein/g of cellulose) were chosen to cover the most commercially practical operating conditions. The sugar and ethanol yields were modeled with good adequacy, showing a positive linear correlation between those yields and refining energy and enzyme loadings. The ethanol yields ranged from 77 to 89 gallons/ODMT of corn stover. The minimum sugar selling price (MSSP) ranged from $0.191 to $0.212 per lb of 50 % concentrated monomeric sugars, while the minimum ethanol selling price (MESP) ranged from $2.24 to $2.54 per gallon of ethanol. The DDR process concept is evaluated for economic feasibility through TEA. The MSSP and MESP of the DDR process falls within a range similar to that found with the deacetylation/dilute acid pretreatment process modeled in NREL’s 2011 design report. The DDR process is a much simpler process that requires less capital and maintenance costs when compared to conventional chemical pretreatments with pressure vessels. As a result, we feel the DDR process should be considered as an option for future biorefineries with great potential to be more cost-effective.« less

Techno-economic analysis of the deacetylation and disk refining process: characterizing the effect of refining energy and enzyme usage on minimum sugar selling price and minimum ethanol selling price.

PubMed

Chen, Xiaowen; Shekiro, Joseph; Pschorn, Thomas; Sabourin, Marc; Tucker, Melvin P; Tao, Ling

2015-01-01

A novel, highly efficient deacetylation and disk refining (DDR) process to liberate fermentable sugars from biomass was recently developed at the National Renewable Energy Laboratory (NREL). The DDR process consists of a mild, dilute alkaline deacetylation step followed by low-energy-consumption disk refining. The DDR corn stover substrates achieved high process sugar conversion yields, at low to modest enzyme loadings, and also produced high sugar concentration syrups at high initial insoluble solid loadings. The sugar syrups derived from corn stover are highly fermentable due to low concentrations of fermentation inhibitors. The objective of this work is to evaluate the economic feasibility of the DDR process through a techno-economic analysis (TEA). A large array of experiments designed using a response surface methodology was carried out to investigate the two major cost-driven operational parameters of the novel DDR process: refining energy and enzyme loadings. The boundary conditions for refining energy (128-468 kWh/ODMT), cellulase (Novozyme's CTec3) loading (11.6-28.4 mg total protein/g of cellulose), and hemicellulase (Novozyme's HTec3) loading (0-5 mg total protein/g of cellulose) were chosen to cover the most commercially practical operating conditions. The sugar and ethanol yields were modeled with good adequacy, showing a positive linear correlation between those yields and refining energy and enzyme loadings. The ethanol yields ranged from 77 to 89 gallons/ODMT of corn stover. The minimum sugar selling price (MSSP) ranged from $0.191 to $0.212 per lb of 50 % concentrated monomeric sugars, while the minimum ethanol selling price (MESP) ranged from $2.24 to $2.54 per gallon of ethanol. The DDR process concept is evaluated for economic feasibility through TEA. The MSSP and MESP of the DDR process falls within a range similar to that found with the deacetylation/dilute acid pretreatment process modeled in NREL's 2011 design report. The DDR process is a much simpler process that requires less capital and maintenance costs when compared to conventional chemical pretreatments with pressure vessels. As a result, we feel the DDR process should be considered as an option for future biorefineries with great potential to be more cost-effective.

Detecting dark energy in orbit: The cosmological chameleon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine

2004-12-15

We show that the chameleon scalar field can drive the current phase of cosmic acceleration for a large class of scalar potentials that are also consistent with local tests of gravity. These provide explicit realizations of a quintessence model where the quintessence scalar field couples directly to baryons and dark matter with gravitational strength. We analyze the cosmological evolution of the chameleon field and show the existence of an attractor solution with the chameleon following the minimum of its effective potential. For a wide range of initial conditions, spanning many orders of magnitude in initial chameleon energy density, the attractormore » is reached before nucleosynthesis. Surprisingly, the range of allowed initial conditions leading to a successful cosmology is wider than in normal quintessence. We discuss applications to the cyclic model of the universe and show how the chameleon mechanism weakens some of the constraints on cyclic potentials.« less

Spatial decision support system to evaluate crop residue energy potential by anaerobic digestion.

PubMed

Escalante, Humberto; Castro, Liliana; Gauthier-Maradei, Paola; Rodríguez De La Vega, Reynel

2016-11-01

Implementing anaerobic digestion (AD) in energy production from crop residues requires development of decision tools to assess its feasibility and sustainability. A spatial decision support system (SDSS) was constructed to assist decision makers to select appropriate feedstock according to biomethanation potential, identify the most suitable location for biogas facilities, determine optimum plant capacity and supply chain, and evaluate associated risks and costs. SDSS involves a spatially explicit analysis, fuzzy multi-criteria analysis, and statistical and optimization models. The tool was validated on seven crop residues located in Santander, Colombia. For example, fique bagasse generates about 0.21millionm(3)CH4year(-1) (0.329m(3)CH4kg(-1) volatile solids) with a minimum profitable plant of about 2000tonyear(-1) and an internal rate of return of 10.5%. SDSS can be applied to evaluate other biomass resources, availability periods, and co-digestion potential. Copyright © 2016. Published by Elsevier Ltd.

Computed potential energy surfaces for chemical reactions

NASA Technical Reports Server (NTRS)

Walch, Stephen P.; Levin, Eugene

1993-01-01

A new global potential energy surface (PES) is being generated for O(P-3) + H2 yields OH + H. This surface is being fit using the rotated Morse oscillator method, which was used to fit the previous POL-CI surface. The new surface is expected to be more accurate and also includes a much more complete sampling of bent geometries. A new study has been undertaken of the reaction N + O2 yields NO + O. The new studies have focused on the region of the surface near a possible minimum corresponding to the peroxy form of NOO. A large portion of the PES for this second reaction has been mapped out. Since state to state cross sections for the reaction are important in the chemistry of high temperature air, these studies will probably be extended to permit generation of a new global potential for reaction.

A potential-of-mean-force approach for fracture mechanics of heterogeneous materials using the lattice element method

NASA Astrophysics Data System (ADS)

Laubie, Hadrien; Radjaï, Farhang; Pellenq, Roland; Ulm, Franz-Josef

2017-08-01

Fracture of heterogeneous materials has emerged as a critical issue in many engineering applications, ranging from subsurface energy to biomedical applications, and requires a rational framework that allows linking local fracture processes with global fracture descriptors such as the energy release rate, fracture energy and fracture toughness. This is achieved here by means of a local and a global potential-of-mean-force (PMF) inspired Lattice Element Method (LEM) approach. In the local approach, fracture-strength criteria derived from the effective interaction potentials between mass points are shown to exhibit a scaling commensurable with the energy dissipation of fracture processes. In the global PMF-approach, fracture is considered as a sequence of equilibrium states associated with minimum potential energy states analogous to Griffith's approach. It is found that this global approach has much in common with a Grand Canonical Monte Carlo (GCMC) approach, in which mass points are randomly removed following a maximum dissipation criterion until the energy release rate reaches the fracture energy. The duality of the two approaches is illustrated through the application of the PMF-inspired LEM for fracture propagation in a homogeneous linear elastic solid using different means of evaluating the energy release rate. Finally, by application of the method to a textbook example of fracture propagation in a heterogeneous material, it is shown that the proposed PMF-inspired LEM approach captures some well-known toughening mechanisms related to fracture energy contrast, elasticity contrast and crack deflection in the considered two-phase layered composite material.

DETERMINING MINIMUM IGNITION ENERGIES AND QUENCHING DISTANCES OF DIFFICULT-TO-IGNITE COMPOUNDS

EPA Science Inventory

Minimum spark energies and corresponding flat-plate electrode quenching distances required to initiate propagation of a combustion wave have been experimentally measured for four flammable hydrofluorocarbon (HFC) refrigerants and propane using ASTM (American Society for Testing a...

Economic, Environmental and Health Implications of Enhanced Ventilation in Office Buildings.

PubMed

MacNaughton, Piers; Pegues, James; Satish, Usha; Santanam, Suresh; Spengler, John; Allen, Joseph

2015-11-18

Current building ventilation standards are based on acceptable minimums. Three decades of research demonstrates the human health benefits of increased ventilation above these minimums. Recent research also shows the benefits on human decision-making performance in office workers, which translates to increased productivity. However, adoption of enhanced ventilation strategies is lagging. We sought to evaluate two of the perceived potential barriers to more widespread adoption-Economic and environmental costs. We estimated the energy consumption and associated per building occupant costs for office buildings in seven U.S. cities, representing different climate zones for three ventilation scenarios (standard practice (20 cfm/person), 30% enhanced ventilation, and 40 cfm/person) and four different heating, ventilation and air conditioning (HVAC) system strategies (Variable Air Volume (VAV) with reheat and a Fan Coil Unit (FCU), both with and without an energy recovery ventilator). We also estimated emissions of greenhouse gases associated with this increased energy usage, and, for comparison, converted this to the equivalent number of vehicles using greenhouse gas equivalencies. Lastly, we paired results from our previous research on cognitive function and ventilation with labor statistics to estimate the economic benefit of increased productivity associated with increasing ventilation rates. Doubling the ventilation rate from the American Society of Heating, Refrigeration and Air-Conditioning Engineers minimum cost less than $40 per person per year in all climate zones investigated. Using an energy recovery ventilation system significantly reduced energy costs, and in some scenarios led to a net savings. At the highest ventilation rate, adding an ERV essentially neutralized the environmental impact of enhanced ventilation (0.03 additional cars on the road per building across all cities). The same change in ventilation improved the performance of workers by 8%, equivalent to a $6500 increase in employee productivity each year. Reduced absenteeism and improved health are also seen with enhanced ventilation. The health benefits associated with enhanced ventilation rates far exceed the per-person energy costs relative to salary costs. Environmental impacts can be mitigated at regional, building, and individual-level scales through the transition to renewable energy sources, adoption of energy efficient systems and ventilation strategies, and promotion of other sustainable policies.

Economic, Environmental and Health Implications of Enhanced Ventilation in Office Buildings

PubMed Central

MacNaughton, Piers; Pegues, James; Satish, Usha; Santanam, Suresh; Spengler, John; Allen, Joseph

2015-01-01

Introduction: Current building ventilation standards are based on acceptable minimums. Three decades of research demonstrates the human health benefits of increased ventilation above these minimums. Recent research also shows the benefits on human decision-making performance in office workers, which translates to increased productivity. However, adoption of enhanced ventilation strategies is lagging. We sought to evaluate two of the perceived potential barriers to more widespread adoption—Economic and environmental costs. Methods: We estimated the energy consumption and associated per building occupant costs for office buildings in seven U.S. cities, representing different climate zones for three ventilation scenarios (standard practice (20 cfm/person), 30% enhanced ventilation, and 40 cfm/person) and four different heating, ventilation and air conditioning (HVAC) system strategies (Variable Air Volume (VAV) with reheat and a Fan Coil Unit (FCU), both with and without an energy recovery ventilator). We also estimated emissions of greenhouse gases associated with this increased energy usage, and, for comparison, converted this to the equivalent number of vehicles using greenhouse gas equivalencies. Lastly, we paired results from our previous research on cognitive function and ventilation with labor statistics to estimate the economic benefit of increased productivity associated with increasing ventilation rates. Results: Doubling the ventilation rate from the American Society of Heating, Refrigeration and Air-Conditioning Engineers minimum cost less than $40 per person per year in all climate zones investigated. Using an energy recovery ventilation system significantly reduced energy costs, and in some scenarios led to a net savings. At the highest ventilation rate, adding an ERV essentially neutralized the environmental impact of enhanced ventilation (0.03 additional cars on the road per building across all cities). The same change in ventilation improved the performance of workers by 8%, equivalent to a $6500 increase in employee productivity each year. Reduced absenteeism and improved health are also seen with enhanced ventilation. Conclusions: The health benefits associated with enhanced ventilation rates far exceed the per-person energy costs relative to salary costs. Environmental impacts can be mitigated at regional, building, and individual-level scales through the transition to renewable energy sources, adoption of energy efficient systems and ventilation strategies, and promotion of other sustainable policies. PMID:26593933

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazante, Alexandre P., E-mail: abazante@chem.ufl.edu; Bartlett, Rodney J.; Davidson, E. R.

The benzene radical anion is studied with ab initio coupled-cluster theory in large basis sets. Unlike the usual assumption, we find that, at the level of theory investigated, the minimum energy geometry is non-planar with tetrahedral distortion at two opposite carbon atoms. The anion is well known for its instability to auto-ionization which poses computational challenges to determine its properties. Despite the importance of the benzene radical anion, the considerable attention it has received in the literature so far has failed to address the details of its structure and shape-resonance character at a high level of theory. Here, we examinemore » the dynamic Jahn-Teller effect and its impact on the anion potential energy surface. We find that a minimum energy geometry of C{sub 2} symmetry is located below one D{sub 2h} stationary point on a C{sub 2h} pseudo-rotation surface. The applicability of standard wave function methods to an unbound anion is assessed with the stabilization method. The isotropic hyperfine splitting constants (A{sub iso}) are computed and compared to data obtained from experimental electron spin resonance experiments. Satisfactory agreement with experiment is obtained with coupled-cluster theory and large basis sets such as cc-pCVQZ.« less

Relaxation dynamics of C60

NASA Astrophysics Data System (ADS)

Walsh, Tiffany R.; Wales, David J.

1998-10-01

The relaxation dynamics of C60 from high-energy isomers to Buckminsterfullerene is examined using a master equation approach. An exhaustive catalog of the C60 fullerene isomers containing only five- and six-membered rings is combined with knowledge of the Stone-Wales rearrangements that connect all such isomers. Full geometry optimizations have been performed for all the minima and the transition states which connect them up to six Stone-Wales steps away from the global minimum. A density-functional tight-binding potential was employed to provide a quantum mechanical description of the bonding. The resulting picture of the potential energy landscape reveals a "weeping willow" structure which offers a clear explanation for the relatively long relaxation times observed experimentally. We also predict the most important transient local minima on the annealing pathway.

The impact of surface area, volume, curvature, and Lennard-Jones potential to solvation modeling.

PubMed

Nguyen, Duc D; Wei, Guo-Wei

2017-01-05

This article explores the impact of surface area, volume, curvature, and Lennard-Jones (LJ) potential on solvation free energy predictions. Rigidity surfaces are utilized to generate robust analytical expressions for maximum, minimum, mean, and Gaussian curvatures of solvent-solute interfaces, and define a generalized Poisson-Boltzmann (GPB) equation with a smooth dielectric profile. Extensive correlation analysis is performed to examine the linear dependence of surface area, surface enclosed volume, maximum curvature, minimum curvature, mean curvature, and Gaussian curvature for solvation modeling. It is found that surface area and surfaces enclosed volumes are highly correlated to each other's, and poorly correlated to various curvatures for six test sets of molecules. Different curvatures are weakly correlated to each other for six test sets of molecules, but are strongly correlated to each other within each test set of molecules. Based on correlation analysis, we construct twenty six nontrivial nonpolar solvation models. Our numerical results reveal that the LJ potential plays a vital role in nonpolar solvation modeling, especially for molecules involving strong van der Waals interactions. It is found that curvatures are at least as important as surface area or surface enclosed volume in nonpolar solvation modeling. In conjugation with the GPB model, various curvature-based nonpolar solvation models are shown to offer some of the best solvation free energy predictions for a wide range of test sets. For example, root mean square errors from a model constituting surface area, volume, mean curvature, and LJ potential are less than 0.42 kcal/mol for all test sets. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Energy-efficient algorithm for broadcasting in ad hoc wireless sensor networks.

PubMed

Xiong, Naixue; Huang, Xingbo; Cheng, Hongju; Wan, Zheng

2013-04-12

Broadcasting is a common and basic operation used to support various network protocols in wireless networks. To achieve energy-efficient broadcasting is especially important for ad hoc wireless sensor networks because sensors are generally powered by batteries with limited lifetimes. Energy consumption for broadcast operations can be reduced by minimizing the number of relay nodes based on the observation that data transmission processes consume more energy than data reception processes in the sensor nodes, and how to improve the network lifetime is always an interesting issue in sensor network research. The minimum-energy broadcast problem is then equivalent to the problem of finding the minimum Connected Dominating Set (CDS) for a connected graph that is proved NP-complete. In this paper, we introduce an Efficient Minimum CDS algorithm (EMCDS) with help of a proposed ordered sequence list. EMCDS does not concern itself with node energy and broadcast operations might fail if relay nodes are out of energy. Next we have proposed a Minimum Energy-consumption Broadcast Scheme (MEBS) with a modified version of EMCDS, and aimed at providing an efficient scheduling scheme with maximized network lifetime. The simulation results show that the proposed EMCDS algorithm can find smaller CDS compared with related works, and the MEBS can help to increase the network lifetime by efficiently balancing energy among nodes in the networks.

Ab initio anharmonic vibrational frequency predictions for linear proton-bound complexes OC-H(+)-CO and N(2)-H(+)-N(2).

PubMed

Terrill, Kasia; Nesbitt, David J

2010-08-01

Ab initio anharmonic transition frequencies are calculated for strongly coupled (i) asymmetric and (ii) symmetric proton stretching modes in the X-H(+)-X linear ionic hydrogen bonded complexes for OCHCO(+) and N(2)HN(2)(+). The optimized potential surface is calculated in these two coordinates for each molecular ion at CCSD(T)/aug-cc-pVnZ (n = 2-4) levels and extrapolated to the complete-basis-set limit (CBS). Slices through both 2D surfaces reveal a relatively soft potential in the asymmetric proton stretching coordinate at near equilibrium geometries, which rapidly becomes a double minimum potential with increasing symmetric proton acceptor center of mass separation. Eigenvalues are obtained by solution of the 2D Schrödinger equation with potential/kinetic energy coupling explicity taken into account, converged in a distributed Gaussian basis set as a function of grid density. The asymmetric proton stretch fundamental frequency for N(2)HN(2)(+) is predicted at 848 cm(-1), with strong negative anharmonicity in the progression characteristic of a shallow "particle in a box" potential. The corresponding proton stretch fundamental for OCHCO(+) is anomalously low at 386 cm(-1), but with a strong alternation in the vibrational spacing due to the presence of a shallow D(infinityh) transition state barrier (Delta = 398 cm(-1)) between the two equivalent minimum geometries. Calculation of a 2D dipole moment surface and transition matrix elements reveals surprisingly strong combination and difference bands with appreciable intensity throughout the 300-1500 cm(-1) region. Corrected for zero point (DeltaZPE) and thermal vibrational excitation (DeltaE(vib)) at 300 K, the single and double dissociation energies in these complexes are in excellent agreement with thermochemical gas phase ion data.

Equilibrium Droplets on Deformable Substrates: Equilibrium Conditions.

PubMed

Koursari, Nektaria; Ahmed, Gulraiz; Starov, Victor M

2018-05-15

Equilibrium conditions of droplets on deformable substrates are investigated, and it is proven using Jacobi's sufficient condition that the obtained solutions really provide equilibrium profiles of both the droplet and the deformed support. At the equilibrium, the excess free energy of the system should have a minimum value, which means that both necessary and sufficient conditions of the minimum should be fulfilled. Only in this case, the obtained profiles provide the minimum of the excess free energy. The necessary condition of the equilibrium means that the first variation of the excess free energy should vanish, and the second variation should be positive. Unfortunately, the mentioned two conditions are not the proof that the obtained profiles correspond to the minimum of the excess free energy and they could not be. It is necessary to check whether the sufficient condition of the equilibrium (Jacobi's condition) is satisfied. To the best of our knowledge Jacobi's condition has never been verified for any already published equilibrium profiles of both the droplet and the deformable substrate. A simple model of the equilibrium droplet on the deformable substrate is considered, and it is shown that the deduced profiles of the equilibrium droplet and deformable substrate satisfy the Jacobi's condition, that is, really provide the minimum to the excess free energy of the system. To simplify calculations, a simplified linear disjoining/conjoining pressure isotherm is adopted for the calculations. It is shown that both necessary and sufficient conditions for equilibrium are satisfied. For the first time, validity of the Jacobi's condition is verified. The latter proves that the developed model really provides (i) the minimum of the excess free energy of the system droplet/deformable substrate and (ii) equilibrium profiles of both the droplet and the deformable substrate.

Minimum energy dissipation required for a logically irreversible operation

NASA Astrophysics Data System (ADS)

Takeuchi, Naoki; Yoshikawa, Nobuyuki

2018-01-01

According to Landauer's principle, the minimum heat emission required for computing is linked to logical entropy, or logical reversibility. The validity of Landauer's principle has been investigated for several decades and was finally demonstrated in recent experiments by showing that the minimum heat emission is associated with the reduction in logical entropy during a logically irreversible operation. Although the relationship between minimum heat emission and logical reversibility is being revealed, it is not clear how much free energy is required to be dissipated for a logically irreversible operation. In the present study, in order to reveal the connection between logical reversibility and free energy dissipation, we numerically demonstrated logically irreversible protocols using adiabatic superconductor logic. The calculation results of work during the protocol showed that, while the minimum heat emission conforms to Landauer's principle, the free energy dissipation can be arbitrarily reduced by performing the protocol quasistatically. The above results show that logical reversibility is not associated with thermodynamic reversibility, and that heat is not only emitted from logic devices but also absorbed by logic devices. We also formulated the heat emission from adiabatic superconductor logic during a logically irreversible operation at a finite operation speed.

Potential Energy Curves and Transport Properties for the Interaction of He with Other Ground-state Atoms

NASA Technical Reports Server (NTRS)

Partridge, Harry; Stallcop, James R.; Levin, Eugene; Arnold, Jim (Technical Monitor)

2001-01-01

The interactions of a He atom with a heavier atom are examined for 26 different elements, which are consecutive members selected from three rows (Li - Ne, Na - Ar, and K,Ca, Ga - Kr) and column 12 (Zn,Cd) of the periodic table. Interaction energies are determined wing high-quality ab initio calculations for the states of the molecule that would be formed from each pair of atoms in their ground states. Potential energies are tabulated for a broad range of Interatomic separation distances. The results show, for example, that the energy of an alkali interaction at small separations is nearly the same as that of a rare-gas interaction with the same electron configuration for the dosed shells. Furthermore, the repulsive-range parameter for this region is very short compared to its length for the repulsion dominated by the alkali-valence electron at large separations (beyond about 3-4 a(sub 0)). The potential energies in the region of the van der Waals minimum agree well with the most accurate results available. The ab initio energies are applied to calculate scattering cross sections and obtain the collision integrals that are needed to determine transport properties to second order. The theoretical values of Li-He total scattering cross sections and the rare-gas atom-He transport properties agree well (to within about 1%) with the corresponding measured data. Effective potential energies are constructed from the ab initio energies; the results have been shown to reproduce known transport data and can be readily applied to predict unknown transport properties for like-atom interactions.

Concentrated energy addition for active drag reduction in hypersonic flow regime

NASA Astrophysics Data System (ADS)

Ashwin Ganesh, M.; John, Bibin

2018-01-01

Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of "optimum energy addition location" have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.

Mars double-aeroflyby free returns

NASA Astrophysics Data System (ADS)

Jesick, Mark

2017-09-01

Mars double-flyby free-return trajectories that pass twice through the Martian atmosphere are documented. This class of trajectories is advantageous for potential Mars atmospheric sample return missions because of its low geocentric energy at departure and arrival, because it would enable two sample collections at unique locations during different Martian seasons, and because of its lack of deterministic maneuvers. Free return opportunities are documented over Earth departure dates ranging from 2015 through 2100, with viable missions available every Earth-Mars synodic period. After constraining the maximum lift-to-drag ratio to be less than one, the minimum observed Earth departure hyperbolic excess speed is 3.23 km/s, the minimum Earth atmospheric entry speed is 11.42 km/s, and the minimum round-trip flight time is 805 days. An algorithm using simplified dynamics is developed along with a method to derive an initial estimate for trajectories in a more realistic dynamic model. Multiple examples are presented, including free returns that pass outside and inside of Mars's appreciable atmosphere.

Preferred orientation of albumin adsorption on a hydrophilic surface from molecular simulation.

PubMed

Hsu, Hao-Jen; Sheu, Sheh-Yi; Tsay, Ruey-Yug

2008-12-01

In general, non-specific protein adsorption follows a two-step procedure, i.e. first adsorption onto a surface in native form, and a subsequent conformational change on the surface. In order to predict the subsequent conformational change, it is important to determine the preferred orientation of an adsorbed protein in the first step of the adsorption. In this work, a method based on finding the global minimum of the interaction potential energy of an adsorbed protein has been developed to delineate the preferred orientations for the adsorption of human serum albumin (HSA) on a model surface with a hydrophilic self-assembled monolayer (SAM). For computational efficiency, solvation effects were greatly simplified by only including the dampening of electrostatic effects while neglecting contributions due to the competition of water molecules for the functional groups on the surface. A contour map obtained by systematic rotation of a molecule in conjunction with perpendicular motion to the surface gives the minimum interaction energy of the adsorbed molecule at various adsorption orientations. Simulation results show that for an -OH terminated SAM surface, a "back-on" orientation of HSA is the preferred orientation. The projection area of this adsorption orientation corresponds with the "triangular-side-on" adsorption of a heart shaped HSA molecule. The method proposed herein is able to provide results which are consistent with those predicted by Monte Carlo (MC) simulations with a substantially less computing cost. The high computing efficiency of the current method makes it possible to be implemented as a design tool for the control of protein adsorption on surfaces; however, before this can be fully realized, these methods must be further developed to enable interaction free energy to be calculated in place of potential energy, along with a more realistic representation of solvation effects.

Torsional energy levels of CH₃OH⁺/CH₃OD⁺/CD₃OD⁺ studied by zero-kinetic energy photoelectron spectroscopy and theoretical calculations.

PubMed

Dai, Zuyang; Gao, Shuming; Wang, Jia; Mo, Yuxiang

2014-10-14

The torsional energy levels of CH3OH(+), CH3OD(+), and CD3OD(+) have been determined for the first time using one-photon zero kinetic energy photoelectron spectroscopy. The adiabatic ionization energies for CH3OH, CH3OD, and CD3OD are determined as 10.8396, 10.8455, and 10.8732 eV with uncertainties of 0.0005 eV, respectively. Theoretical calculations have also been performed to obtain the torsional energy levels for the three isotopologues using a one-dimensional model with approximate zero-point energy corrections of the torsional potential energy curves. The calculated values are in good agreement with the experimental data. The barrier height of the torsional potential energy without zero-point energy correction was calculated as 157 cm(-1), which is about half of that of the neutral (340 cm(-1)). The calculations showed that the cation has eclipsed conformation at the energy minimum and staggered one at the saddle point, which is the opposite of what is observed in the neutral molecule. The fundamental C-O stretch vibrational energy level for CD3OD(+) has also been determined. The energy levels for the combinational excitation of the torsional vibration and the fundamental C-O stretch vibration indicate a strong torsion-vibration coupling.

Molecular electrostatics for probing lone pair-π interactions.

PubMed

Mohan, Neetha; Suresh, Cherumuttathu H; Kumar, Anmol; Gadre, Shridhar R

2013-11-14

An electrostatics-based approach has been proposed for probing the weak interactions between lone pair containing molecules and π deficient molecular systems. For electron-rich molecules, the negative minima in molecular electrostatic potential (MESP) topography give the location of electron localization and the MESP value at the minimum (Vmin) quantifies the electron-rich character of that region. Interactive behavior of a lone pair bearing molecule with electron deficient π-systems, such as hexafluorobenzene, 1,3,5-trinitrobenzene, 2,4,6-trifluoro-1,3,5-triazine and 1,2,4,5-tetracyanobenzene explored within DFT brings out good correlation of the lone pair-π interaction energy (E(int)) with the Vmin value of the electron-rich system. Such interaction is found to be portrayed well with the Electrostatic Potential for Intermolecular Complexation (EPIC) model. On the basis of the precise location of MESP minimum, a prediction for the orientation of a lone pair bearing molecule with an electron deficient π-system is possible in the majority of the cases studied.

Gaussian process regression to accelerate geometry optimizations relying on numerical differentiation

NASA Astrophysics Data System (ADS)

Schmitz, Gunnar; Christiansen, Ove

2018-06-01

We study how with means of Gaussian Process Regression (GPR) geometry optimizations, which rely on numerical gradients, can be accelerated. The GPR interpolates a local potential energy surface on which the structure is optimized. It is found to be efficient to combine results on a low computational level (HF or MP2) with the GPR-calculated gradient of the difference between the low level method and the target method, which is a variant of explicitly correlated Coupled Cluster Singles and Doubles with perturbative Triples correction CCSD(F12*)(T) in this study. Overall convergence is achieved if both the potential and the geometry are converged. Compared to numerical gradient-based algorithms, the number of required single point calculations is reduced. Although introducing an error due to the interpolation, the optimized structures are sufficiently close to the minimum of the target level of theory meaning that the reference and predicted minimum only vary energetically in the μEh regime.

A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H2

NASA Astrophysics Data System (ADS)

Denis-Alpizar, Otoniel; Kalugina, Yulia; Stoecklin, Thierry; Vera, Mario Hernández; Lique, François

2013-12-01

We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H2. Ab initio calculations of the HCN-H2 van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN-H2 with the nitrogen pointing towards H2 at an intermolecular separation of 7.20 a0. The corresponding well depth is -195.20 cm-1. A secondary minimum of -183.59 cm-1 was found for a T-shape configuration with the H of HCN pointing to the center of mass of H2. We also determine the rovibrational energy levels of the HCN-para-H2 and HCN-ortho-H2 complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm-1 and 60.26 cm-1, respectively. The calculated ro-vibrational transitions in the HCN-H2 complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

Potential Arbitrage Revenue of Energy Storage Systems in PJM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salles, Mauricio; Huang, Junling; Aziz, Michael

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), the largest U.S. regional transmission organization, using hourly locational marginal prices over the seven-year period 2008–2014. Assuming a price-taking ESS with perfect foresight in the real-time market, we optimized the charge-discharge profile to determine the maximum potential revenue for a 1 MW system as a function of energy/power ratio, or rated discharge duration, from 1 to 14more » h, including a limited analysis of sensitivity to round-trip efficiency. We determined minimum potential revenue with a similar analysis of the day-ahead market. We presented the distribution over the set of nodes and years of price, price volatility, and maximum potential arbitrage revenue. From these results, we determined the break even overnight installed cost of an ESS below which arbitrage would be profitable, its dependence on rated discharge duration, its distribution over grid nodes, and its variation over the years. We showed that dispatch into real-time markets based on day-ahead market settlement prices is a simple, feasible method that raises the lower bound on the achievable arbitrage revenue.« less

Potential Arbitrage Revenue of Energy Storage Systems in PJM

DOE PAGES

Salles, Mauricio; Huang, Junling; Aziz, Michael; ...

2017-07-27

The volatility of electricity prices is attracting interest in the opportunity of providing net revenue by energy arbitrage. We analyzed the potential revenue of a generic Energy Storage System (ESS) in 7395 different locations within the electricity markets of Pennsylvania-New Jersey-Maryland interconnection (PJM), the largest U.S. regional transmission organization, using hourly locational marginal prices over the seven-year period 2008–2014. Assuming a price-taking ESS with perfect foresight in the real-time market, we optimized the charge-discharge profile to determine the maximum potential revenue for a 1 MW system as a function of energy/power ratio, or rated discharge duration, from 1 to 14more » h, including a limited analysis of sensitivity to round-trip efficiency. We determined minimum potential revenue with a similar analysis of the day-ahead market. We presented the distribution over the set of nodes and years of price, price volatility, and maximum potential arbitrage revenue. From these results, we determined the break even overnight installed cost of an ESS below which arbitrage would be profitable, its dependence on rated discharge duration, its distribution over grid nodes, and its variation over the years. We showed that dispatch into real-time markets based on day-ahead market settlement prices is a simple, feasible method that raises the lower bound on the achievable arbitrage revenue.« less

Information dynamics in living systems: prokaryotes, eukaryotes, and cancer.

PubMed

Frieden, B Roy; Gatenby, Robert A

2011-01-01

Living systems use information and energy to maintain stable entropy while far from thermodynamic equilibrium. The underlying first principles have not been established. We propose that stable entropy in living systems, in the absence of thermodynamic equilibrium, requires an information extremum (maximum or minimum), which is invariant to first order perturbations. Proliferation and death represent key feedback mechanisms that promote stability even in a non-equilibrium state. A system moves to low or high information depending on its energy status, as the benefit of information in maintaining and increasing order is balanced against its energy cost. Prokaryotes, which lack specialized energy-producing organelles (mitochondria), are energy-limited and constrained to an information minimum. Acquisition of mitochondria is viewed as a critical evolutionary step that, by allowing eukaryotes to achieve a sufficiently high energy state, permitted a phase transition to an information maximum. This state, in contrast to the prokaryote minima, allowed evolution of complex, multicellular organisms. A special case is a malignant cell, which is modeled as a phase transition from a maximum to minimum information state. The minimum leads to a predicted power-law governing the in situ growth that is confirmed by studies measuring growth of small breast cancers. We find living systems achieve a stable entropic state by maintaining an extreme level of information. The evolutionary divergence of prokaryotes and eukaryotes resulted from acquisition of specialized energy organelles that allowed transition from information minima to maxima, respectively. Carcinogenesis represents a reverse transition: of an information maximum to minimum. The progressive information loss is evident in accumulating mutations, disordered morphology, and functional decline characteristics of human cancers. The findings suggest energy restriction is a critical first step that triggers the genetic mutations that drive somatic evolution of the malignant phenotype.

The structure, energetics, and nature of the chemical bonding of phenylthiol adsorbed on the Au(111) surface: implications for density-functional calculations of molecular-electronic conduction.

PubMed

Bilić, Ante; Reimers, Jeffrey R; Hush, Noel S

2005-03-01

The adsorption of phenylthiol on the Au(111) surface is modeled using Perdew and Wang density-functional calculations. Both direct molecular physisorption and dissociative chemisorption via S-H bond cleavage are considered as well as dimerization to form disulfides. For the major observed product, the chemisorbed thiol, an extensive potential-energy surface is produced as a function of both the azimuthal orientation of the adsorbate and the linear translation of the adsorbate through the key fcc, hcp, bridge, and top binding sites. Key structures are characterized, the lowest-energy one being a broad minimum of tilted orientation ranging from the bridge structure halfway towards the fcc one. The vertically oriented threefold binding sites, often assumed to dominate molecular electronics measurements, are identified as transition states at low coverage but become favored in dense monolayers. A similar surface is also produced for chemisorption of phenylthiol on Ag(111); this displays significant qualitative differences, consistent with the qualitatively different observed structures for thiol chemisorption on Ag and Au. Full contours of the minimum potential energy as a function of sulfur translation over the crystal face are described, from which the barrier to diffusion is deduced to be 5.8 kcal mol(-1), indicating that the potential-energy surface has low corrugation. The calculated bond lengths, adsorbate charge and spin density, and the density of electronic states all indicate that, at all sulfur locations, the adsorbate can be regarded as a thiyl species that forms a net single covalent bond to the surface of strength 31 kcal mol(-1). No detectable thiolate character is predicted, however, contrary to experimental results for alkyl thiols that indicate up to 20%-30% thiolate involvement. This effect is attributed to the asymptotic-potential error of all modern density functionals that becomes manifest through a 3-4 eV error in the lineup of the adsorbate and substrate bands. Significant implications are described for density-functional calculations of through-molecule electron transport in molecular electronics.

Lumbar load attenuation for rotorcraft occupants using a design methodology for the seat impact energy-absorbing system

NASA Astrophysics Data System (ADS)

Moradi, Rasoul; Beheshti, Hamid K.; Lankarani, Hamid M.

2012-12-01

Aircraft occupant crash-safety considerations require a minimum cushion thickness to limit the relative vertical motion of the seat-pelvis during high vertical impact loadings in crash landings or accidents. In military aircraft and helicopter seat design, due to the potential for high vertical accelerations in crash scenarios, the seat system must be provided with an energy absorber to attenuate the acceleration level sustained by the occupants. Because of the limited stroke available for the seat structure, the design of the energy absorber becomes a trade-off problem between minimizing the stroke and maximizing the energy absorption. The available stroke must be used to prevent bottoming out of the seat as well as to absorb maximum impact energy to protect the occupant. In this study, the energy-absorbing system in a rotorcraft seat design is investigated using a mathematical model of the occupant/seat system. Impact theories between interconnected bodies in multibody mechanical systems are utilized to study the impact between the seat pan and the occupant. Experimental responses of the seat system and the occupant are utilized to validate the results from this study for civil and military helicopters according to FAR 23 and 25 and MIL-S-58095 requirements. A model for the load limiter is proposed to minimize the lumbar load for the occupant by minimizing the relative velocity between the seat pan and the occupant's pelvis. The modified energy absorber/load limiter is then implemented for the seat structure so that it absorbs the energy of impact in an effective manner and below the tolerable limit for the occupant in a minimum stroke. Results show that for a designed stroke, the level of occupant lumbar spine injury would be significantly attenuated using this modified energy-absorber system.

A general intermolecular force field based on tight-binding quantum chemical calculations

NASA Astrophysics Data System (ADS)

Grimme, Stefan; Bannwarth, Christoph; Caldeweyher, Eike; Pisarek, Jana; Hansen, Andreas

2017-10-01

A black-box type procedure is presented for the generation of a molecule-specific, intermolecular potential energy function. The method uses quantum chemical (QC) information from our recently published extended tight-binding semi-empirical scheme (GFN-xTB) and can treat non-covalently bound complexes and aggregates with almost arbitrary chemical structure. The necessary QC information consists of the equilibrium structure, Mulliken atomic charges, charge centers of localized molecular orbitals, and also of frontier orbitals and orbital energies. The molecular pair potential includes model density dependent Pauli repulsion, penetration, as well as point charge electrostatics, the newly developed D4 dispersion energy model, Drude oscillators for polarization, and a charge-transfer term. Only one element-specific and about 20 global empirical parameters are needed to cover systems with nuclear charges up to radon (Z = 86). The method is tested for standard small molecule interaction energy benchmark sets where it provides accurate intermolecular energies and equilibrium distances. Examples for structures with a few hundred atoms including charged systems demonstrate the versatility of the approach. The method is implemented in a stand-alone computer code which enables rigid-body, global minimum energy searches for molecular aggregation or alignment.

Competition between quasi-planar and cage-like structures in the B29- cluster: photoelectron spectroscopy and ab initio calculations.

PubMed

Li, Hai-Ru; Jian, Tian; Li, Wei-Li; Miao, Chang-Qing; Wang, Ying-Jin; Chen, Qiang; Luo, Xue-Mei; Wang, Kang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

2016-10-26

Size-selected boron clusters have been found to be predominantly planar or quasi-planar (2D) in the small size regime with the appearance of three-dimensional (3D) borospherene cages of larger sizes. A seashell-like B 28 - cluster was previously shown to be the smallest borospherene, which competes with a quasi-planar isomer for the global minimum. Here we report a study on the structures and bonding of the B 29 - and B 29 clusters using photoelectron spectroscopy (PES) and first-principles calculations and demonstrate the continued competition between the 2D and borospherene structures. The PES spectrum of B 29 - displays a complex pattern with evidence of low-lying isomers. Global-minimum searches and extensive theoretical calculations revealed a complicated potential energy surface for B 29 - with five low-lying isomers, among which the lowest three were shown to contribute to the experimental spectrum. A 3D seashell-like C s (2, 1 A') isomer, featuring two heptagons on the waist and one octagon at the bottom, is the global minimum for B 29 - , followed by a 2D C 1 (3, 1 A) isomer with a hexagonal hole and a stingray-shaped 2D C s (1, 1 A') isomer with a pentagonal hole. However, by taking into account the entropic effects, the stingray-shaped isomer 1 was shown to be the lowest in energy at room temperature and was found to dominate the PES spectrum. Isomers 2 and 3, which have lower electron binding energies, were also found to be present in the experiment. Chemical bonding analyses showed that isomer 1 is an all-boron analogue of benzo[ghi]fluoranthene (C 18 H 10 ), whereas the borospherene isomer 2 possesses 18π electrons, conforming to the 2(N + 1) 2 electron counting rule for spherical aromaticity. For the B 29 neutral cluster, the seashell-like borospherene isomer is the global minimum, significantly lower in energy than the stingray-shaped quasi-planar structure.

Colloid transport in saturated porous media: Elimination of attachment efficiency in a new colloid transport model

USGS Publications Warehouse

Landkamer, Lee L.; Harvey, Ronald W.; Scheibe, Timothy D.; Ryan, Joseph N.

2013-01-01

A colloid transport model is introduced that is conceptually simple yet captures the essential features of colloid transport and retention in saturated porous media when colloid retention is dominated by the secondary minimum because an electrostatic barrier inhibits substantial deposition in the primary minimum. This model is based on conventional colloid filtration theory (CFT) but eliminates the empirical concept of attachment efficiency. The colloid deposition rate is computed directly from CFT by assuming all predicted interceptions of colloids by collectors result in at least temporary deposition in the secondary minimum. Also, a new paradigm for colloid re-entrainment based on colloid population heterogeneity is introduced. To accomplish this, the initial colloid population is divided into two fractions. One fraction, by virtue of physiochemical characteristics (e.g., size and charge), will always be re-entrained after capture in a secondary minimum. The remaining fraction of colloids, again as a result of physiochemical characteristics, will be retained “irreversibly” when captured by a secondary minimum. Assuming the dispersion coefficient can be estimated from tracer behavior, this model has only two fitting parameters: (1) the fraction of the initial colloid population that will be retained “irreversibly” upon interception by a secondary minimum, and (2) the rate at which reversibly retained colloids leave the secondary minimum. These two parameters were correlated to the depth of the Derjaguin-Landau-Verwey-Overbeek (DLVO) secondary energy minimum and pore-water velocity, two physical forces that influence colloid transport. Given this correlation, the model serves as a heuristic tool for exploring the influence of physical parameters such as surface potential and fluid velocity on colloid transport.

Principle of Minimum Energy in Magnetic Reconnection in a Self-organized Critical Model for Solar Flares

NASA Astrophysics Data System (ADS)

Farhang, Nastaran; Safari, Hossein; Wheatland, Michael S.

2018-05-01

Solar flares are an abrupt release of magnetic energy in the Sun’s atmosphere due to reconnection of the coronal magnetic field. This occurs in response to turbulent flows at the photosphere that twist the coronal field. Similar to earthquakes, solar flares represent the behavior of a complex system, and expectedly their energy distribution follows a power law. We present a statistical model based on the principle of minimum energy in a coronal loop undergoing magnetic reconnection, which is described as an avalanche process. We show that the distribution of peaks for the flaring events in this self-organized critical system is scale-free. The obtained power-law index of 1.84 ± 0.02 for the peaks is in good agreement with satellite observations of soft X-ray flares. The principle of minimum energy can be applied for general avalanche models to describe many other phenomena.

Generalized variational approach to Kim-Gordon electron gas theory for ionic crystals

NASA Astrophysics Data System (ADS)

Ivanov, O. V.; Maksimov, E. G.

1996-01-01

The generalized approach to the Kim-Gordon electron gas model is proposed. The total density of a crystal is considered as a superposition of densities of individual overlapping ions. The possible distortions of individual ion densities are calculated in the presence of some auxiliary external potentials. The real values of these distortions are calculated by a variational method from the minimum total energy of a crystal. The proper prescription of the ion self-energy with a distorted density is given using the method elaborated in the nonequilibrium thermodynamics. Some examples of the calculation for phonon frequencies are presented and demonstrate a good agreement with experimental data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xantheas, Sotiris S.; Werhahn, Jasper C.

Based on the formulation of the analytical expression of the potential V(r) describing intermolecular interactions in terms of the dimensionless variables r*=r/rm and !*=V/!, where rm is the separation at the minimum and ! the well depth, we propose more generalized scalable forms for the commonly used Lennard-Jones, Mie, Morse and Buckingham exponential-6 potential energy functions (PEFs). These new generalized forms have an additional parameter from and revert to the original ones for some choice of that parameter. In this respect, the original forms can be considered as special cases of the more general forms that are introduced. We alsomore » propose a scalable, but nonrevertible to the original one, 4-parameter extended Morse potential.« less

Acoustic particle separation

NASA Technical Reports Server (NTRS)

Barmatz, M. B.; Stoneburner, J. D.; Jacobi, N.; Wang, T. (Inventor)

1985-01-01

A method is described which uses acoustic energy to separate particles of different sizes, densities, or the like. The method includes applying acoustic energy resonant to a chamber containing a liquid of gaseous medium to set up a standing wave pattern that includes a force potential well wherein particles within the well are urged towards the center, or position of minimum force potential. A group of particles to be separated is placed in the chamber, while a non-acoustic force such as gravity is applied, so that the particles separate with the larger or denser particles moving away from the center of the well to a position near its edge and progressively smaller lighter particles moving progressively closer to the center of the well. Particles are removed from different positions within the well, so that particles are separated according to the positions they occupy in the well.

Investigation on minimum ignition energy of mixtures of α-pinene-benzene/air.

PubMed

Coudour, B; Chetehouna, K; Rudz, S; Gillard, P; Garo, J P

2015-01-01

Minimum ignition energies (MIE) of α-pinene-benzene/air mixtures at a given temperature for different equivalence ratios and fuel proportions are experimented in this paper. We used a cylindrical chamber of combustion using a nanosecond pulse at 1,064 nm from a Q-switched Nd:YAG laser. Laser-induced spark ignitions were studied for two molar proportions of α-pinene/benzene mixtures, respectively 20-80% and 50-50%. The effect of the equivalence ratio (Φ) has been investigated for 0.7, 0.9, 1.1 and 1.5 and ignition of fuel/air mixtures has been experimented for two different incident laser energies: 25 and 33 mJ. This study aims at observing the influence of different α-pinene/benzene proportions on the flammability of the mixture to have further knowledge of the potential of biogenic volatile organic compounds (BVOCs) and smoke mixtures to influence forest fires, especially in the case of the accelerating forest fire phenomenon (AFF). Results of ignition probability and energy absorption are based on 400 laser shots for each studied fuel proportions. MIE results as functions of equivalence ratio compared to data of pure α-pinene and pure benzene demonstrate that the presence of benzene in α-pinene-air mixture tends to increase ignition probability and reduce MIE without depending strongly on the α-pinene/benzene proportion. Copyright © 2014 Elsevier B.V. All rights reserved.

"Vibrational bonding": a new type of chemical bond is discovered.

PubMed

Rhodes, Christopher J; Macrae, Roderick M

2015-01-01

A long-sought but elusive new type of chemical bond, occurring on a minimum-free, purely repulsive potential energy surface, has recently been convincingly shown to be possible on the basis of high-level quantum-chemical calculations. This type of bond, termed a vibrational bond, forms because the total energy, including the dynamical energy of the nuclei, is lower than the total energy of the dissociated products, including their vibrational zero-point energy. For this to be the case, the ZPE of the product molecule must be very high, which is ensured by replacing a conventional hydrogen atom with its light isotope muonium (Mu, mass = 1/9 u) in the system Br-H-Br, a natural transition state in the reaction between Br and HBr. A paramagnetic species observed in the reaction Mu +Br2 has been proposed as a first experimental sighting of this species, but definitive identification remains challenging.

Exploring load, velocity, and surface disorder dependence of friction with one-dimensional and two-dimensional models.

PubMed

Dagdeviren, Omur E

2018-08-03

The effect of surface disorder, load, and velocity on friction between a single asperity contact and a model surface is explored with one-dimensional and two-dimensional Prandtl-Tomlinson (PT) models. We show that there are fundamental physical differences between the predictions of one-dimensional and two-dimensional models. The one-dimensional model estimates a monotonic increase in friction and energy dissipation with load, velocity, and surface disorder. However, a two-dimensional PT model, which is expected to approximate a tip-sample system more realistically, reveals a non-monotonic trend, i.e. friction is inert to surface disorder and roughness in wearless friction regime. The two-dimensional model discloses that the surface disorder starts to dominate the friction and energy dissipation when the tip and the sample interact predominantly deep into the repulsive regime. Our numerical calculations address that tracking the minimum energy path and the slip-stick motion are two competing effects that determine the load, velocity, and surface disorder dependence of friction. In the two-dimensional model, the single asperity can follow the minimum energy path in wearless regime; however, with increasing load and sliding velocity, the slip-stick movement dominates the dynamic motion and results in an increase in friction by impeding tracing the minimum energy path. Contrary to the two-dimensional model, when the one-dimensional PT model is employed, the single asperity cannot escape to the minimum energy minimum due to constraint motion and reveals only a trivial dependence of friction on load, velocity, and surface disorder. Our computational analyses clarify the physical differences between the predictions of the one-dimensional and two-dimensional models and open new avenues for disordered surfaces for low energy dissipation applications in wearless friction regime.

Communication: An accurate global potential energy surface for the ground electronic state of ozone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawes, Richard, E-mail: dawesr@mst.edu, E-mail: hguo@unm.edu; Lolur, Phalgun; Li, Anyang

We report a new full-dimensional and global potential energy surface (PES) for the O + O{sub 2} → O{sub 3} ozone forming reaction based on explicitly correlated multireference configuration interaction (MRCI-F12) data. It extends our previous [R. Dawes, P. Lolur, J. Ma, and H. Guo, J. Chem. Phys. 135, 081102 (2011)] dynamically weighted multistate MRCI calculations of the asymptotic region which showed the widely found submerged reef along the minimum energy path to be the spurious result of an avoided crossing with an excited state. A spin-orbit correction was added and the PES tends asymptotically to the recently developed long-rangemore » electrostatic model of Lepers et al. [J. Chem. Phys. 137, 234305 (2012)]. This PES features: (1) excellent equilibrium structural parameters, (2) good agreement with experimental vibrational levels, (3) accurate dissociation energy, and (4) most-notably, a transition region without a spurious reef. The new PES is expected to allow insight into the still unresolved issues surrounding the kinetics, dynamics, and isotope signature of ozone.« less

A tale of two superpotentials: Stability and instability in designer gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amsel, Aaron J.; Marolf, Donald; Hertog, Thomas

We investigate the stability of asymptotically anti-de Sitter gravity coupled to tachyonic scalar fields with mass at or slightly above the Breitenlohner-Freedman bound. The boundary conditions in these 'designer gravity' theories are defined in terms of an arbitrary function W. Previous work had suggested that the energy in designer gravity is bounded below if (i) W has a global minimum and (ii) the scalar potential admits a superpotential P. More recently, however, certain solutions were found (numerically) to violate the proposed energy bound. We resolve the discrepancy by observing that a given scalar potential can admit two possible branches ofmore » the corresponding superpotential, P{sub {+-}}. When there is a P{sub -} branch, we rigorously prove a lower bound on the energy; the P{sub +} branch alone is not sufficient. Our numerical investigations (i) confirm this picture, (ii) confirm other critical aspects of the (complicated) proofs, and (iii) suggest that the existence of P{sub -} may in fact be necessary (as well as sufficient) for the energy of a designer gravity theory to be bounded below.« less

Computed potential energy surfaces for chemical reactions

NASA Technical Reports Server (NTRS)

Walch, Stephen P.

1988-01-01

The minimum energy path for the addition of a hydrogen atom to N2 is characterized in CASSCF/CCI calculations using the (4s3p2d1f/3s2p1d) basis set, with additional single point calculations at the stationary points of the potential energy surface using the (5s4p3d2f/4s3p2d) basis set. These calculations represent the most extensive set of ab initio calculations completed to date, yielding a zero point corrected barrier for HN2 dissociation of approx. 8.5 kcal mol/1. The lifetime of the HN2 species is estimated from the calculated geometries and energetics using both conventional Transition State Theory and a method which utilizes an Eckart barrier to compute one dimensional quantum mechanical tunneling effects. It is concluded that the lifetime of the HN2 species is very short, greatly limiting its role in both termolecular recombination reactions and combustion processes.

Charge transfer excitons and image potential states on organic semiconductor surfaces

NASA Astrophysics Data System (ADS)

Yang, Qingxin; Muntwiler, Matthias; Zhu, X.-Y.

2009-09-01

We report two types of excited electronic states on organic semiconductor surfaces: image potential states (IPS) and charge transfer excitons (CTE). In the former, an excited electron is localized in the surface-normal direction by the image potential and delocalized in the surface plane. In the latter, the electron is localized in all directions by both the image potential and the Coulomb potential from a photogenerated hole on an organic molecule. We use crystalline pentacene and tetracene surfaces as model systems, and time- and angle-resolved two-photon photoemission spectroscopy to probe the energetics and dynamics of both the IPS and the CTE states. On either pentacene or tetracene surfaces, we observe delocalized image bands and a series of CT excitons with binding energies <0.5eV below the image-band minimum. The binding energies of these CT excitons agree well with solutions to the atomic-H-like Schrödinger equation based on the image potential and the electron-hole Coulomb potential. We hypothesize that the formation of CT excitons should be general to the surfaces of organic semiconductors where the relatively narrow valance-band width facilitates the localization of the hole and the low dielectric constant ensures strong electron-hole attraction.

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Theis, Daniel; Windus, Theresa L.; Ruedenberg, Klaus

The metastable ring structure of the ozone 1{sup 1}A{sub 1} ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two {sup 1}A{sub 1} states. In the present work, valence correlated energies of the 1{sup 1}A{sub 1} state and the 2{sup 1}A{sub 1} state were calculated at the 1{sup 1}A{sub 1} open minimum, the 1{sup 1}A{sub 1} ring minimum,more » the transition state between these two minima, the minimum of the 2{sup 1}A{sub 1} state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of Correlation Energy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 1{sup 1}A{sub 1} state, the present calculations yield the estimates of (ring minimum—open minimum) ∼45–50 mh and (transition state—open minimum) ∼85–90 mh. For the (2{sup 1}A{sub 1}–{sup 1}A{sub 1}) excitation energy, the estimate of ∼130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2{sup 1}A{sub 1}–{sup 1}A{sub 1}) is found to be between 1 and 10 mh. The geometry of the transition state on the 1{sup 1}A{sub 1} surface and that of the minimum on the 2{sup 1}A{sub 1} surface nearly coincide. More accurate predictions of the energy differences also require CI expansions to at least sextuple excitations with respect to the valence space. For every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

Free energy and hidden barriers of the β-sheet structure of prion protein.

PubMed

Paz, S Alexis; Abrams, Cameron F

2015-10-13

On-the-fly free-energy parametrization is a new collective variable biasing approach akin to metadynamics with one important distinction: rather than acquiring an accelerated distribution via a history-dependent bias potential, sampling on this distribution is achieved from the beginning of the simulation using temperature-accelerated molecular dynamics. In the present work, we compare the performance of both approaches to compute the free-energy profile along a scalar collective variable measuring the H-bond registry of the β-sheet structure of the mouse Prion protein. Both methods agree on the location of the free-energy minimum, but free-energy profiles from well-tempered metadynamics are subject to a much higher degree of statistical noise due to hidden barriers. The sensitivity of metadynamics to hidden barriers is shown to be a consequence of the history dependence of the bias potential, and we detail the nature of these barriers for the prion β-sheet. In contrast, on-the-fly parametrization is much less sensitive to these barriers and thus displays improved convergence behavior relative to that of metadynamics. While hidden barriers are a frequent and central issue in free-energy methods, on-the-fly free-energy parametrization appears to be a robust and preferable method to confront this issue.

Bioelectrochemical system platform for sustainable environmental remediation and energy generation.

PubMed

Wang, Heming; Luo, Haiping; Fallgren, Paul H; Jin, Song; Ren, Zhiyong Jason

2015-01-01

The increasing awareness of the energy-environment nexus is compelling the development of technologies that reduce environmental impacts during energy production as well as energy consumption during environmental remediation. Countries spend billions in pollution cleanup projects, and new technologies with low energy and chemical consumption are needed for sustainable remediation practice. This perspective review provides a comprehensive summary on the mechanisms of the new bioelectrochemical system (BES) platform technology for efficient and low cost remediation, including petroleum hydrocarbons, chlorinated solvents, perchlorate, azo dyes, and metals, and it also discusses the potential new uses of BES approach for some emerging contaminants remediation, such as CO2 in air and nutrients and micropollutants in water. The unique feature of BES for environmental remediation is the use of electrodes as non-exhaustible electron acceptors, or even donors, for contaminant degradation, which requires minimum energy or chemicals but instead produces sustainable energy for monitoring and other onsite uses. BES provides both oxidation (anode) and reduction (cathode) reactions that integrate microbial-electro-chemical removal mechanisms, so complex contaminants with different characteristics can be removed. We believe the BES platform carries great potential for sustainable remediation and hope this perspective provides background and insights for future research and development. Copyright © 2015 Elsevier Inc. All rights reserved.

Guidelines for LTS magnet design based on transient stability

NASA Astrophysics Data System (ADS)

Seo, Kazutaka; Morita, Masao

2006-05-01

Stabilities of low critical temperature superconducting (LTS) magnets and their designs are studied and discussed. There are two contradictory necessities; those are low cost and high performance, in the other words, high magnetic field and large current density. Especially, the maximum magnetic fields of the latest high performance Nb 3Sn magnets are around 20 T. Mentioned necessities result in the small stability margins. Needless to say, the superconducting magnet must produce its nominal field reliably. Therefore, maintaining adequate stability margin, the magnet design to draw out the high potential of the superconductor is required. The transient stability of the superconducting magnet is determined by the relationship between mechanical disturbance energy and stability margin. The minimum quench energy (MQE) is one of the index of stability margin and it is defined as the minimum energy to trigger quenching of a superconductor. MQE should be beyond any possible disturbance energy during the operation. It is difficult to identify the mechanical disturbance energy quantitatively. On the contrary, MQE had been evaluated precisely by means of our developed resistive carbon paste heater (CPH). At the same time, we can predict MQE by numerical simulations. Because the magnet comes to quench if the mechanical disturbance exceeds the MQE, the disturbance energies are suspected to be equivalent to MQEs during the magnet-training. When we achieved somewhat larger MQE, we may exclude numbers of training quenches. In this paper, we discuss the guidelines of LTS magnet design from the standpoint of MQE. We represent some case studies for various superconducting magnets and/or some different winding methods.

A biomimetic, energy-harvesting, obstacle-avoiding, path-planning algorithm for UAVs

NASA Astrophysics Data System (ADS)

Gudmundsson, Snorri

This dissertation presents two new approaches to energy harvesting for Unmanned Aerial Vehicles (UAV). One method is based on the Potential Flow Method (PFM); the other method seeds a wind-field map based on updraft peak analysis and then applies a variant of the Bellman-Ford algorithm to find the minimum-cost path. Both methods are enhanced by taking into account the performance characteristics of the aircraft using advanced performance theory. The combined approach yields five possible trajectories from which the one with the minimum energy cost is selected. The dissertation concludes by using the developed theory and modeling tools to simulate the flight paths of two small Unmanned Aerial Vehicles (sUAV) in the 500 kg and 250 kg class. The results show that, in mountainous regions, substantial energy can be recovered, depending on topography and wind characteristics. For the examples presented, as much as 50% of the energy was recovered for a complex, multi-heading, multi-altitude, 170 km mission in an average wind speed of 9 m/s. The algorithms constitute a Generic Intelligent Control Algorithm (GICA) for autonomous unmanned aerial vehicles that enables an extraction of atmospheric energy while completing a mission trajectory. At the same time, the algorithm. automatically adjusts the flight path in order to avoid obstacles, in a fashion not unlike what one would expect from living organisms, such as birds and insects. This multi-disciplinary approach renders the approach biomimetic, i.e. it constitutes a synthetic system that “mimics the formation and function of biological mechanisms and processes.”.

Floating and Tether-Coupled Adhesion of Bacteria to Hydrophobic and Hydrophilic Surfaces

PubMed Central

2018-01-01

Models for bacterial adhesion to substratum surfaces all include uncertainty with respect to the (ir)reversibility of adhesion. In a model, based on vibrations exhibited by adhering bacteria parallel to a surface, adhesion was described as a result of reversible binding of multiple bacterial tethers that detach from and successively reattach to a surface, eventually making bacterial adhesion irreversible. Here, we use total internal reflection microscopy to determine whether adhering bacteria also exhibit variations over time in their perpendicular distance above surfaces. Streptococci with fibrillar surface tethers showed perpendicular vibrations with amplitudes of around 5 nm, regardless of surface hydrophobicity. Adhering, nonfibrillated streptococci vibrated with amplitudes around 20 nm above a hydrophobic surface. Amplitudes did not depend on ionic strength for either strain. Calculations of bacterial energies from their distances above the surfaces using the Boltzman equation showed that bacteria with fibrillar tethers vibrated as a harmonic oscillator. The energy of bacteria without fibrillar tethers varied with distance in a comparable fashion as the DLVO (Derjaguin, Landau, Verwey, and Overbeek)-interaction energy. Distance variations above the surface over time of bacteria with fibrillar tethers are suggested to be governed by the harmonic oscillations, allowed by elasticity of the tethers, piercing through the potential energy barrier. Bacteria without fibrillar tethers “float” above a surface in the secondary energy minimum, with their perpendicular displacement restricted by their thermal energy and the width of the secondary minimum. The distinction between “tether-coupled” and “floating” adhesion is new, and may have implications for bacterial detachment strategies. PMID:29649869

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

DOE PAGES

Theis, Daniel; Ivanic, Joseph; Windus, Theresa L.; ...

2016-03-10

The metastable ring structure of the ozone 1 1A 1 ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two 1A 1 states. In the present work, valence correlated energies of the 1 1A 1 state and the 2 1A 1 state were calculated at the 1 1A 1 open minimum, the 1 1A 1 ring minimum, themore » transition state between these two minima, the minimum of the 2 1A 1 state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of CorrelationEnergy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 11A1 state, the present calculations yield the estimates of (ring minimum—open minimum) ~45–50 mh and (transition state—open minimum) ~85–90 mh. For the (2 1A 1– 1A 1) excitation energy, the estimate of ~130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2 1A 1– 1A 1) is found to be between 1 and 10 mh. The geometry of the transition state on the 11A1 surface and that of the minimum on the 2 1A 1 surface nearly coincide. More accurate predictions of the energydifferences also require CI expansions to at least sextuple excitations with respect to the valence space. Furthermore, for every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Theis, Daniel; Ivanic, Joseph; Windus, Theresa L.

The metastable ring structure of the ozone 1 1A 1 ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two 1A 1 states. In the present work, valence correlated energies of the 1 1A 1 state and the 2 1A 1 state were calculated at the 1 1A 1 open minimum, the 1 1A 1 ring minimum, themore » transition state between these two minima, the minimum of the 2 1A 1 state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of CorrelationEnergy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 11A1 state, the present calculations yield the estimates of (ring minimum—open minimum) ~45–50 mh and (transition state—open minimum) ~85–90 mh. For the (2 1A 1– 1A 1) excitation energy, the estimate of ~130–170 mh is found at the open minimum and 270–310 mh at the ring minimum. At the transition state, the difference (2 1A 1– 1A 1) is found to be between 1 and 10 mh. The geometry of the transition state on the 11A1 surface and that of the minimum on the 2 1A 1 surface nearly coincide. More accurate predictions of the energydifferences also require CI expansions to at least sextuple excitations with respect to the valence space. Furthermore, for every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences.« less

The reversibility of virus attachment to mineral surfaces

USGS Publications Warehouse

Loveland, J.P.; Ryan, J.N.; Amy, G.L.; Harvey, R.W.

1996-01-01

Virus transport through groundwater is limited by attachment to mineral surfaces and inactivation. Current virus transport models do not consider the implications of the reversibility of virus attachment to minerals. To explore the reversibility of virus attachment to mineral surfaces, we attached PRD1, a bacteriophage considered to be a good model of enteric viruses, to quartz and ferric oxyhydroxide-coated quartz surfaces over a range of pH values in equilibrium 'static columns'. Following attachment, we detached the viruses by replacing the pore solution with solutions of equal and higher pH. The extent of virus attachment followed an attachment 'edge' that occurred at a pH value about 2.5-3.5 pH units above the pH(IEP) of the mineral surfaces. Viruses attached below this edge were irreversibly attached until the pH of the detachment solution exceeded the pH value of the attachment edge. Viruses attached above this edge were reversibly attached. Derjaguin-Landau-Verwey-Overbeek (DEVO) potential energy calculations showed that the attachment edge occurred at the pH at which the potential energy of the primary minimum was near zero, implying that the position of the primary minimum (attractive or repulsive) controlled the equilibrium distribution of the viruses. The results suggest that the reversibility of virus attachment must be considered in virus transport models for accurate predictions of virus travel time.

DLVO, hydrophobic, capillary and hydrodynamic forces acting on bacteria at solid-air-water interfaces: Their relative impact on bacteria deposition mechanisms in unsaturated porous media.

PubMed

Bai, Hongjuan; Cochet, Nelly; Pauss, André; Lamy, Edvina

2017-02-01

Experimental and modeling studies were performed to investigate bacteria deposition behavior in unsaturated porous media. The coupled effect of different forces, acting on bacteria at solid-air-water interfaces and their relative importance on bacteria deposition mechanisms was explored by calculating Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO interactions such as hydrophobic, capillary and hydrodynamic forces. Negatively charged non-motile bacteria and quartz sands were used in packed column experiments. The breakthrough curves and retention profiles of bacteria were simulated using the modified Mobile-IMmobile (MIM) model, to identify physico-chemical attachment or physical straining mechanisms involved in bacteria retention. These results indicated that both mechanisms might occur in both sand. However, the attachment was found to be a reversible process, because attachment coefficients were similar to those of detachment. DLVO calculations supported these results: the primary minimum did not exist, suggesting no permanent retention of bacteria to solid-water and air-water interfaces. Calculated hydrodynamic and resisting torques predicted that bacteria detachment in the secondary minimum might occur. The capillary potential energy was greater than DLVO, hydrophobic and hydrodynamic potential energies, suggesting that film straining by capillary forces might largely govern bacteria deposition under unsaturated conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Spectroscopic determination of the intermolecular potential energy surface for Ar-NH3

NASA Astrophysics Data System (ADS)

Schmuttenmaer, C. A.; Cohen, R. C.; Saykally, R. J.

1994-07-01

The three-dimensional intermolecular potential energy surface (IPS) for Ar-NH3 has been determined from a least-squares fit to 61 far infrared and microwave vibration-rotation-tunneling (VRT) measurements and to temperature-dependent second virial coefficients. The three intermolecular coordinates (R,θ,φ) are treated without invoking any approximations regarding their separability, and the NH3 inversion-tunneling motion is included adiabatically. A surface with 13 variable parameters has been optimized to accurately reproduce the spectroscopic observables, using the collocation method to treat the coupled multidimensional dynamics within a scattering formalism. Anisotropy in the IPS is found to significantly mix the free rotor basis functions. The 149.6 cm-1 global minimum on this surface occurs with the NH3 symmetry axis nearly perpendicular to the van der Waals bond axis (θ=96.6°), at a center-of-mass separation of 3.57 Å, and with the Ar atom midway between two of the NH3 hydrogen atoms (φ=60°). The position of the global minimum is very different from the center-of-mass distance extracted from microwave spectroscopic studies. Long-range (R≳3.8 Å) attractive interactions are greatest when either a N-H bond or the NH3 lone pair is directed toward the argon. Comparisons with ab initio surfaces for this molecule as well as the experimentally determined IPS for Ar-H2O are presented.

Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

NASA Astrophysics Data System (ADS)

Han, Huixian; Li, Anyang; Guo, Hua

2014-12-01

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ˜37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm-1. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm-1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.

Axial propulsion with flapping and rotating wings, a comparison of potential efficiency.

PubMed

Kroninger, Christopher M

2018-04-18

Interest in biological locomotion and what advantages the principles governing it might offer in the design of manmade vehicles prompts one to consider the power requirements of flapping relative to rotary propulsion. The amount of work performed on the fluid surrounding a thrusting surface (wing or blade) is reflected in the kinetic energy of the wake. Consideration of the energy in the wake is sufficient to define absolute minimum limitations on the power requirement to generate a particular thrust. This work applies wake solutions to compare the minimum inviscid propulsive power requirement of wings flapping and in rotation at wing loading conditions reflective of hover through a state of lightly-loaded cruise. It is demonstrated that hovering flapping flight is less efficient than rotary wing propulsion except for the most extreme flap amplitude strokes ([Formula: see text]   >  160°) if operating at large wake wavelength. In cruise, a larger range of flap amplitude kinematics ([Formula: see text]  >  140°) can be aerodynamically more energy efficient for wake wavelengths reflective of biological propulsion. These results imply, based on the observed wing kinematics of continuous steady flight, that flapping propulsion in animals is unlikely to be more efficient than rotary propulsion.

Temporal change in the electromechanical properties of dielectric elastomer minimum energy structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buchberger, G., E-mail: erda.buchberger@jku.at; Hauser, B.; Jakoby, B.

Dielectric elastomer minimum energy structures (DEMES) are soft electronic transducers and energy harvesters with potential for consumer goods. The temporal change in their electromechanical properties is of major importance for engineering tasks. Therefore, we study acrylic DEMES by impedance spectroscopy and by optical methods for a total time period of approx. 4.5 months. We apply either compliant electrodes from carbon black particles only or fluid electrodes from a mixture of carbon black particles and silicone oil. From the measurement data, the equivalent series capacitances and resistances as well as the bending angles of the transducers are obtained. We find thatmore » the equivalent series capacitances change in average between −12 %/1000 h and −4.0 %/1000 h, while the bending angles decrease linearly with slopes ranging from −15 %/1000 h to −7 %/1000 h. Transducers with high initial bending angles and electrodes from carbon black particles show the smallest changes of the electromechanical characteristics. The capacitances decrease faster for DEMES with fluid electrodes. Some DEMES of this type reveal huge and unpredictable fluctuations of the resistances over time due to the ageing of the contacts. Design guidelines for DEMES follow directly from the observed transient changes of their electromechanical performance.« less

Ignition threshold for non-Maxwellian plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hay, Michael J., E-mail: hay@princeton.edu; Fisch, Nathaniel J.; Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543

2015-11-15

An optically thin p-{sup 11}B plasma loses more energy to bremsstrahlung than it gains from fusion reactions, unless the ion temperature can be elevated above the electron temperature. In thermal plasmas, the temperature differences required are possible in small Coulomb logarithm regimes, characterized by high density and low temperature. Ignition could be reached more easily if the fusion reactivity can be improved with nonthermal ion distributions. To establish an upper bound for the potential utility of a nonthermal distribution, we consider a monoenergetic beam with particle energy selected to maximize the beam-thermal reactivity. Comparing deuterium-tritium (DT) and p-{sup 11}B, themore » minimum Lawson criteria and minimum ρR required for inertial confinement fusion (ICF) volume ignition are calculated with and without the nonthermal feature. It turns out that channeling fusion alpha energy to maintain such a beam facilitates ignition at lower densities and ρR, improves reactivity at constant pressure, and could be used to remove helium ash. On the other hand, the reactivity gains that could be realized in DT plasmas are significant, the excess electron density in p-{sup 11}B plasmas increases the recirculated power cost to maintain a nonthermal feature and thereby constrains its utility to ash removal.« less

Energy Efficiency Building Code for Commercial Buildings in Sri Lanka

DOE Office of Scientific and Technical Information (OSTI.GOV)

Busch, John; Greenberg, Steve; Rubinstein, Francis

2000-09-30

1.1.1 To encourage energy efficient design or retrofit of commercial buildings so that they may be constructed, operated, and maintained in a manner that reduces the use of energy without constraining the building function, the comfort, health, or the productivity of the occupants and with appropriate regard for economic considerations. 1.1.2 To provide criterion and minimum standards for energy efficiency in the design or retrofit of commercial buildings and provide methods for determining compliance with them. 1.1.3 To encourage energy efficient designs that exceed these criterion and minimum standards.

The effect of weight and drag on the sinking speed and lift/drag ratio of gliders

NASA Technical Reports Server (NTRS)

Kosin, R

1934-01-01

The most important factors in evaluating performance of gliders are minimum sinking speed and minimum gliding angle. To assure their optimum value the energy necessary for flight, that is, the energy of lift and friction must be kept very low, or in other words, weight and total drag which have a decisive effect on the sinking speed and on the gliding angle, must be kept to a minimum. How great the effect of a reduction of these two quantities will be shown in the following.

An explanation for the tiny value of the cosmological constant and the low vacuum energy density

NASA Astrophysics Data System (ADS)

Nassif, Cláudio

2015-09-01

The paper aims to provide an explanation for the tiny value of the cosmological constant and the low vacuum energy density to represent the dark energy. To accomplish this, we will search for a fundamental principle of symmetry in space-time by means of the elimination of the classical idea of rest, by including an invariant minimum limit of speed in the subatomic world. Such a minimum speed, unattainable by particles, represents a preferred reference frame associated with a background field that breaks down the Lorentz symmetry. The metric of the flat space-time shall include the presence of a uniform vacuum energy density, which leads to a negative pressure at cosmological length scales. Thus, the equation of state for the cosmological constant [ p(pressure) (energy density)] naturally emerges from such a space-time with an energy barrier of a minimum speed. The tiny values of the cosmological constant and the vacuum energy density will be successfully obtained, being in agreement with the observational results of Perlmutter, Schmidt and Riess.

Potential Energy Surface-Based Automatic Deduction of Conformational Transition Networks and Its Application on Quantum Mechanical Landscapes of d-Glucose Conformers.

PubMed

Satoh, Hiroko; Oda, Tomohiro; Nakakoji, Kumiyo; Uno, Takeaki; Tanaka, Hiroaki; Iwata, Satoru; Ohno, Koichi

2016-11-08

This paper describes our approach that is built upon the potential energy surface (PES)-based conformational analysis. This approach automatically deduces a conformational transition network, called a conformational reaction route map (r-map), by using the Scaled Hypersphere Search of the Anharmonic Downward Distortion Following method (SHS-ADDF). The PES-based conformational search has been achieved by using large ADDF, which makes it possible to trace only low transition state (TS) barriers while restraining bond lengths and structures with high free energy. It automatically performs sampling the minima and TS structures by simply taking into account the mathematical feature of PES without requiring any a priori specification of variable internal coordinates. An obtained r-map is composed of equilibrium (EQ) conformers connected by reaction routes via TS conformers, where all of the reaction routes are already confirmed during the process of the deduction using the intrinsic reaction coordinate (IRC) method. The postcalculation analysis of the deduced r-map is interactively carried out using the RMapViewer software we have developed. This paper presents computational details of the PES-based conformational analysis and its application to d-glucose. The calculations have been performed for an isolated glucose molecule in the gas phase at the RHF/6-31G level. The obtained conformational r-map for α-d-glucose is composed of 201 EQ and 435 TS conformers and that for β-d-glucose is composed of 202 EQ and 371 TS conformers. For the postcalculation analysis of the conformational r-maps by using the RMapViewer software program we have found multiple minimum energy paths (MEPs) between global minima of 1 C 4 and 4 C 1 chair conformations. The analysis using RMapViewer allows us to confirm the thermodynamic and kinetic predominance of 4 C 1 conformations; that is, the potential energy of the global minimum of 4 C 1 is lower than that of 1 C 4 (thermodynamic predominance) and that the highest energy of those of all the TS structures along a route from 4 C 1 to 1 C 4 is lower than that of 1 C 4 to 4 C 1 (kinetic predominance).

Prospective Evaluation of the Energy and CO 2 Emissions Impact of China’s 2010 – 2013 Efficiency Standards for Products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khanna, Nina; Zhou, Nan; Fridley, David

Since China introduced its first mandatory minimum energy performance standards (MEPS) for eight major household products in 1989, its MEPS program has expanded significantly to cover nearly 60 residential, industrial and commercial products. In June of 2012, the pace of standards development for new and revised standards was further accelerated with the launch of the national “100 Energy Efficiency Standards.” Initiatives. An unprecedented 21 MEPS were adopted by China from 2012 to 2013, compared to only 7 MEPS adopted from 2010 to 2011. The Chinese MEPS program now covers 15 products in the residential sector, 15 types of commercial andmore » office equipment, 14 types of industrial equipment and 13 lighting products, making it one of the most comprehensive MEPS program in the world. This study provides an updated prospective evaluation of the potential energy and CO 2 impact of 23 of the 28 MEPS adopted by China from 2010 to 2013. This study updates a previous analysis (Zhou et al. 2011) by quantifying the additional potential energy and CO 2 reductions from the newest standards that have been adopted since 2010. The most recent actual and projected sales, usage, and efficiency data were collected for 14 product categories covered under 23 MEPS adopted between 2010 and 2013. Three scenarios are then used to quantify the energy and CO 2 reduction potential of the one-time implementation of these 23 MEPS, including a baseline counterfactual scenario, the actual MEPS scenario and a best available technologies efficiency scenario. The setting of the baseline efficiency is crucial to determining the savings potential of the new and revised MEPS and international best available technology efficiency levels, as it reflects the market average in the absence of MEPS. For this study, the average baseline is based on either the reported 2010 market-average efficiency if sales-weighted efficiency data is available for new product MEPS and selected products with revised MEPS, or the minimum efficiency requirement of the previous MEPS for products with revised MEPS from 2010 to 2013 that do not have sales-weighted efficiency data. Using sales-weighted efficiency data for the baseline help capture market transformation that has already occurred prior to the implementation of the MEPS, and can better differentiate the savings that are attributable to MEPS. The efficiency levels of best available technologies are taken from recent reviews of international commercially available best available technologies.« less

Potential Coastal Pumped Hydroelectric Energy Storage Locations Identified using GIS-based Topographic Analysis

NASA Astrophysics Data System (ADS)

Parsons, R.; Barnhart, C. J.; Benson, S. M.

2013-12-01

Large-scale electrical energy storage could accommodate variable, weather dependent energy resources such as wind and solar. Pumped hydroelectric energy storage (PHS) and compressed energy storage area (CAES) have life cycle energy and financial costs that are an order of magnitude lower than conventional electrochemical storage technologies. However PHS and CAES storage technologies require specific geologic conditions. Conventional PHS requires an upper and lower reservoir separated by at least 100 m of head, but no more than 10 km in horizontal distance. Conventional PHS also impacts fresh water supplies, riparian ecosystems, and hydrologic environments. A PHS facility that uses the ocean as the lower reservoir benefits from a smaller footprint, minimal freshwater impact, and the potential to be located near off shore wind resources and population centers. Although technologically nascent, today one coastal PHS facility exists. The storage potential for coastal PHS is unknown. Can coastal PHS play a significant role in augmenting future power grids with a high faction of renewable energy supply? In this study we employ GIS-based topographic analysis to quantify the coastal PHS potential of several geographic locations, including California, Chile and Peru. We developed automated techniques that seek local topographic minima in 90 m spatial resolution shuttle radar topography mission (SRTM) digital elevation models (DEM) that satisfy the following criteria conducive to PHS: within 10 km from the sea; minimum elevation 150 m; maximum elevation 1000 m. Preliminary results suggest the global potential for coastal PHS could be very significant. For example, in northern Chile we have identified over 60 locations that satisfy the above criteria. Two of these locations could store over 10 million cubic meters of water or several GWh of energy. We plan to report a global database of candidate coastal PHS locations and to estimate their energy storage capacity.

Structure, dynamics, and thermodynamics of a family of potentials with tunable softness

NASA Astrophysics Data System (ADS)

Shi, Zane; Debenedetti, Pablo G.; Stillinger, Frank H.; Ginart, Paul

2011-08-01

We investigate numerically the structure, thermodynamics, and relaxation behavior of a family of (n, 6) Lennard-Jones-like glass-forming binary mixtures interacting via pair potentials with variable softness, fixed well depth, and fixed well depth location. These constraints give rise to progressively more negative attractive tails upon softening, for separations greater than the potential energy minimum. Over the range of conditions examined, we find only modest dependence of structure on softness. In contrast, decreasing the repulsive exponent from n = 12 to n = 7 causes the diffusivity to increase by as much as two orders of magnitude at fixed temperature and density, and produces mechanically stable packings (inherent structures) with cohesive energies that are, on average, ˜1.7 well depths per particle larger than for the corresponding Lennard-Jones (n = 12) case. The softer liquids have markedly higher entropies and lower Kauzmann temperatures than their Lennard-Jones (n = 12) counterparts, and they remain diffusive down to appreciably lower temperatures. We find that softening leads to a modest increase in fragility.

Transient low-barrier hydrogen bond in the photoactive state of green fluorescent protein.

PubMed

Nadal-Ferret, Marc; Gelabert, Ricard; Moreno, Miquel; Lluch, José M

2015-12-14

In this paper, we have analyzed the feasibility of spontaneous proton transfer in GFP at the Franck-Condon region directly after photoexcitation. Computation of a sizeable portion of the potential energy surface at the Franck-Condon region of A the structure shows the process of proton transfer to be unfavorable by 3 kcal mol(-1) in S1 if no further structural relaxation is permitted. The ground vibrational state is found to lie above the potential energy barrier of the proton transfer in both S0 and S1. Expectation values of the geometry reveal that the proton shared between the chromophore and W22, and the proton shared between Ser205 and Glu222 are very close to the center of the respective hydrogen bonds, giving support to the claim that the first transient intermediate detected after photoexcitation (I0*) has characteristics similar to those of a low-barrier hydrogen bond [Di Donato et al., Phys. Chem. Chem. Phys., 2012, 13, 16295]. A quantum dynamical calculation of the evolution in the excited state shows an even larger probability of finding those two protons close to the center compared to in the ground state, but no formation of the proton-transferred product is observed. A QM/MM photoactive state geometry optimization, initiated using a configuration obtained by taking the A minimum and moving the protons to the product side, yields a minimum energy structure with the protons transferred and in which the His148 residue is substantially closer to the now anionic chromophore. These results indicate that: (1) proton transfer is not possible if structural relaxation of the surroundings of the chromophore is prevented; (2) protons H1 and H3 especially are found very close to the point halfway between the donor and acceptor after photoexcitation when the zero-point energy is considered; (3) a geometrical parameter exists (the His148-Cro distance) under which the structure with the protons transferred is not a minimum, and that, if included, should lead to the fluorescing I* structure. The existence of an oscillating stationary state between the reactants and products of the triple proton transfer reaction can explain the dual emission reported for the I0* intermediate of wtGFP.

Evaluation of energy savings potential of variable refrigerant flow (VRF) from variable air volume (VAV) in the U.S. climate locations

DOE PAGES

Kim, Dongsu; Cox, Sam J.; Cho, Heejin; ...

2017-05-22

Variable refrigerant flow (VRF) systems are known for their high energy performance and thus can improve energy efficiency both in residential and commercial buildings. The energy savings potential of this system has been demonstrated in several studies by comparing the system performance with conventional HVAC systems such as rooftop variable air volume systems (RTU-VAV) and central chiller and boiler systems. This paper evaluates the performance of VRF and RTU-VAV systems in a simulation environment using widely-accepted whole building energy modeling software, EnergyPlus. A medium office prototype building model, developed by the U.S. Department of Energy (DOE), is used to assessmore » the performance of VRF and RTU-VAV systems. Each system is placed in 16 different locations, representing all U.S. climate zones, to evaluate the performance variations. Both models are compliant with the minimum energy code requirements prescribed in ASHRAE standard 90.1-2010 — energy standard for buildings except low-rise residential buildings. Finally, a comparison study between the simulation results of VRF and RTU-VAV models is made to demonstrate energy savings potential of VRF systems. The simulation results show that the VRF systems would save around 15–42% and 18–33% for HVAC site and source energy uses compared to the RTU-VAV systems. In addition, calculated results for annual HVAC cost savings point out that hot and mild climates show higher percentage cost savings for the VRF systems than cold climates mainly due to the differences in electricity and gas use for heating sources.« less

Evaluation of energy savings potential of variable refrigerant flow (VRF) from variable air volume (VAV) in the U.S. climate locations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Dongsu; Cox, Sam J.; Cho, Heejin

Variable refrigerant flow (VRF) systems are known for their high energy performance and thus can improve energy efficiency both in residential and commercial buildings. The energy savings potential of this system has been demonstrated in several studies by comparing the system performance with conventional HVAC systems such as rooftop variable air volume systems (RTU-VAV) and central chiller and boiler systems. This paper evaluates the performance of VRF and RTU-VAV systems in a simulation environment using widely-accepted whole building energy modeling software, EnergyPlus. A medium office prototype building model, developed by the U.S. Department of Energy (DOE), is used to assessmore » the performance of VRF and RTU-VAV systems. Each system is placed in 16 different locations, representing all U.S. climate zones, to evaluate the performance variations. Both models are compliant with the minimum energy code requirements prescribed in ASHRAE standard 90.1-2010 — energy standard for buildings except low-rise residential buildings. Finally, a comparison study between the simulation results of VRF and RTU-VAV models is made to demonstrate energy savings potential of VRF systems. The simulation results show that the VRF systems would save around 15–42% and 18–33% for HVAC site and source energy uses compared to the RTU-VAV systems. In addition, calculated results for annual HVAC cost savings point out that hot and mild climates show higher percentage cost savings for the VRF systems than cold climates mainly due to the differences in electricity and gas use for heating sources.« less

Quantum theory of rotational isomerism and Hill equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ugulava, A.; Toklikishvili, Z.; Chkhaidze, S.

2012-06-15

The process of rotational isomerism of linear triatomic molecules is described by the potential with two different-depth minima and one barrier between them. The corresponding quantum-mechanical equation is represented in the form that is a special case of the Hill equation. It is shown that the Hill-Schroedinger equation has a Klein's quadratic group symmetry which, in its turn, contains three invariant subgroups. The presence of these subgroups makes it possible to create a picture of energy spectrum which depends on a parameter and has many merging and branch points. The parameter-dependent energy spectrum of the Hill-Schroedinger equation, like Mathieu-characteristics, containsmore » branch points from the left and from the right of the demarcation line. However, compared to the Mathieu-characteristics, in the Hill-Schroedinger equation spectrum the 'right' points are moved away even further for some distance that is the bigger, the bigger is the less deep well. The asymptotic wave functions of the Hill-Schroedinger equation for the energy values near the potential minimum contain two isolated sharp peaks indicating a possibility of the presence of two stable isomers. At high energy values near the potential maximum, the height of two peaks decreases, and between them there appear chaotic oscillations. This form of the wave functions corresponds to the process of isomerization.« less

Bookending the Opportunity to Lower Wind’s LCOE by Reducing the Uncertainty Surrounding Annual Energy Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolinger, Mark

Reducing the performance risk surrounding a wind project can potentially lead to a lower weighted-average cost of capital (WACC), and hence a lower levelized cost of energy (LCOE), through an advantageous shift in capital structure, and possibly also a reduction in the cost of capital. Specifically, a reduction in performance risk will move the 1-year P99 annual energy production (AEP) estimate closer to the P50 AEP estimate, which in turn reduces the minimum debt service coverage ratio (DSCR) required by lenders, thereby allowing the project to be financed with a greater proportion of low-cost debt. In addition, a reduction inmore » performance risk might also reduce the cost of one or more of the three sources of capital that are commonly used to finance wind projects: sponsor or cash equity, tax equity, and/or debt. Preliminary internal LBNL analysis of the maximum possible LCOE reduction attainable from reducing the performance risk of a wind project found a potentially significant opportunity for LCOE reduction of ~$10/MWh, by reducing the P50 DSCR to its theoretical minimum value of 1.0 (Bolinger 2015b, 2014) and by reducing the cost of sponsor equity and debt by one-third to one-half each (Bolinger 2015a, 2015b). However, with FY17 funding from the U.S. Department of Energy’s Atmosphere to Electrons (A2e) Performance Risk, Uncertainty, and Finance (PRUF) initiative, LBNL has been revisiting this “bookending” exercise in more depth, and now believes that its earlier preliminary assessment of the LCOE reduction opportunity was overstated. This reassessment is based on two new-found understandings: (1) Due to ever-present and largely irreducible inter-annual variability (IAV) in the wind resource, the minimum required DSCR cannot possibly fall to 1.0 (on a P50 basis), and (2) A reduction in AEP uncertainty will not necessarily lead to a reduction in the cost of capital, meaning that a shift in capital structure is perhaps the best that can be expected (perhaps along with a modest decline in the cost of cash equity as new investors enter the market).« less

Performance evaluation of the inverse dynamics method for optimal spacecraft reorientation

NASA Astrophysics Data System (ADS)

Ventura, Jacopo; Romano, Marcello; Walter, Ulrich

2015-05-01

This paper investigates the application of the inverse dynamics in the virtual domain method to Euler angles, quaternions, and modified Rodrigues parameters for rapid optimal attitude trajectory generation for spacecraft reorientation maneuvers. The impact of the virtual domain and attitude representation is numerically investigated for both minimum time and minimum energy problems. Owing to the nature of the inverse dynamics method, it yields sub-optimal solutions for minimum time problems. Furthermore, the virtual domain improves the optimality of the solution, but at the cost of more computational time. The attitude representation also affects solution quality and computational speed. For minimum energy problems, the optimal solution can be obtained without the virtual domain with any considered attitude representation.

From molecule to solid: The prediction of organic crystal structures

NASA Astrophysics Data System (ADS)

Dzyabchenko, A. V.

2008-10-01

A method for predicting the structure of a molecular crystal based on the systematic search for a global potential energy minimum is considered. The method takes into account unequal occurrences of the structural classes of organic crystals and symmetry of the multidimensional configuration space. The programs of global minimization PMC, comparison of crystal structures CRYCOM, and approximation to the distributions of the electrostatic potentials of molecules FitMEP are presented as tools for numerically solving the problem. Examples of predicted structures substantiated experimentally and the experience of author’s participation in international tests of crystal structure prediction organized by the Cambridge Crystallographic Data Center (Cambridge, UK) are considered.

Exponential 6 parameterization for the JCZ3-EOS

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGee, B.C.; Hobbs, M.L.; Baer, M.R.

1998-07-01

A database has been created for use with the Jacobs-Cowperthwaite-Zwisler-3 equation-of-state (JCZ3-EOS) to determine thermochemical equilibrium for detonation and expansion states of energetic materials. The JCZ3-EOS uses the exponential 6 intermolecular potential function to describe interactions between molecules. All product species are characterized by r*, the radius of the minimum pair potential energy, and {var_epsilon}/k, the well depth energy normalized by Boltzmann`s constant. These parameters constitute the JCZS (S for Sandia) EOS database describing 750 gases (including all the gases in the JANNAF tables), and have been obtained by using Lennard-Jones potential parameters, a corresponding states theory, pure liquid shockmore » Hugoniot data, and fit values using an empirical EOS. This database can be used with the CHEETAH 1.40 or CHEETAH 2.0 interface to the TIGER computer program that predicts the equilibrium state of gas- and condensed-phase product species. The large JCZS-EOS database permits intermolecular potential based equilibrium calculations of energetic materials with complex elemental composition.« less

Research requirements for emergency power to permit hover-one-engine-inoperative helicopter operation

NASA Technical Reports Server (NTRS)

Yost, J. H.

1976-01-01

The research and technology demonstration requirements to achieve emergency-power capability for a civil helicopter are documented. The goal for emergency power is the ability to hover with one engine inoperative, transition to minimum-power forward flight, and continue to a safe landing where emergency power may or may not be required. The best method to obtain emergency power is to augment the basic engine power by increasing the engine's speed and turbine-inlet temperature, combined with water-alcohol injection at the engine inlet. Other methods, including turbine boost power and flywheel energy, offer potential for obtaining emergency power for minimum time durations. Costs and schedules are estimated for a research and development program to bring emergency power through a hardware-demonstration test. Interaction of engine emergency-power capability with other helicopter systems is examined.

Standard model false vacuum inflation: correlating the tensor-to-scalar ratio to the top quark and Higgs boson masses.

PubMed

Masina, Isabella; Notari, Alessio

2012-05-11

For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10(16)  GeV, where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0±3.5  GeV, where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, A.M.; Ruzic, D.N.; Powell, R.C.

An analyzer capable of determining the mass as well as the energy (5--200 eV) of neutral and ion species has been developed from a quadrupole mass spectrometer (QMS). The system, which is similar to a retarding grid energy analyzer (RGEA), functions by biasing the rods of a QMS and monitoring the analyzer signal as a function of bias potential. Modulation of the pole bias greatly increases the minimum detectable signal level. Experiments were performed using species generated in a single-grid Kaufman ion gun operated with N{sub 2} or Ar. Results show that the pole bias techniques can provide energy resolutionmore » of 1--2 eV. Ion species from the gun were found to have an energy equal to the sum of the beam and the plasma potentials, with an energy spread between 1 and 3 eV. Fast N{sub 2} and Ar neutral species were measured as a function of discharge voltage (30--80 V), beam acceleration voltage (50--100 V), grid voltage ({minus}20 to +5 V), and pressure (0.5 and 1.5 mTorr). The energy of the fast neutral species was always less than that of the ions. This was consistent with the fast neutrals being formed by a charge-exchange process.« less

Energy and Cost Savings of Retro-Commissioning and Retrofit Measures for Large Office Buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Weimin; Zhang, Jian; Moser, Dave

2012-08-03

This paper evaluates the energy and cost savings of seven retro-commissioning measures and 29 retrofit measures applicable to most large office buildings. The baseline model is for a hypothetical building with characteristics of large office buildings constructed before 1980. Each retro-commissioning measure is evaluated against the original baseline in terms of its potential of energy and cost savings while each retrofit measure is evaluated against the commissioned building. All measures are evaluated in five locations (Miami, Las Vegas, Seattle, Chicago and Duluth) to understand the impact of weather conditions on energy and cost savings. The results show that implementation ofmore » the seven operation and maintenance measures as part of a retro-commissioning process can yield an average of about 22% of energy use reduction and 14% of energy cost reduction. Widening zone temperature deadband, lowering VAV terminal minimum air flow set points and lighting upgrades are effective retrofit measures to be considered.« less

Minimum energy requirements for desalination of brackish groundwater in the United States with comparison to international datasets

USGS Publications Warehouse

Ahdab, Yvana D.; Thiel, Gregory P.; Böhlke, John Karl; Stanton, Jennifer S.; Lienhard, John H.

2018-01-01

This paper uses chemical and physical data from a large 2017 U.S. Geological Surveygroundwater dataset with wells in the U.S. and three smaller international groundwater datasets with wells primarily in Australia and Spain to carry out a comprehensive investigation of brackish groundwater composition in relation to minimum desalinationenergy costs. First, we compute the site-specific least work required for groundwater desalination. Least work of separation represents a baseline for specific energy consumptionof desalination systems. We develop simplified equations based on the U.S. data for least work as a function of water recovery ratio and a proxy variable for composition, either total dissolved solids, specific conductance, molality or ionic strength. We show that the U.S. correlations for total dissolved solids and molality may be applied to the international datasets. We find that total molality can be used to calculate the least work of dilute solutions with very high accuracy. Then, we examine the effects of groundwater solute composition on minimum energy requirements, showing that separation requirements increase from calcium to sodium for cations and from sulfate to bicarbonate to chloride for anions, for any given TDS concentration. We study the geographic distribution of least work, total dissolved solids, and major ions concentration across the U.S. We determine areas with both low least work and high water stress in order to highlight regions holding potential for desalination to decrease the disparity between high water demand and low water supply. Finally, we discuss the implications of the USGS results on water resource planning, by comparing least work to the specific energy consumption of brackish water reverse osmosisplants and showing the scaling propensity of major electrolytes and silica in the U.S. groundwater samples.

Naringenin and quercetin--potential anti-HCV agents for NS2 protease targets.

PubMed

Lulu, S Sajitha; Thabitha, A; Vino, S; Priya, A Mohana; Rout, Madhusmita

2016-01-01

Nonstructural proteins of hepatitis C virus had drawn much attention for the scientific fraternity in drug discovery due to its important role in the disease. 3D structure of the protein was predicted using molecular modelling protocol. Docking studies of 10 medicinal plant compounds and three drugs available in the market (control) with NS2 protease were employed by using rigid docking approach of AutoDock 4.2. Among the molecules tested for docking study, naringenin and quercetin revealed minimum binding energy of - 7.97 and - 7.95 kcal/mol with NS2 protease. All the ligands were docked deeply within the binding pocket region of the protein. The docking study results showed that these compounds are potential inhibitors of the target; and also all these docked compounds have good inhibition constant, vdW+Hbond+desolv energy with best RMSD value.

Research on Buckling State of Prestressed Fiber-Strengthened Steel Pipes

NASA Astrophysics Data System (ADS)

Wang, Ruheng; Lan, Kunchang

2018-01-01

The main restorative methods of damaged oil and gas pipelines include welding reinforcement, fixture reinforcement and fiber material reinforcement. Owing to the severe corrosion problems of pipes in practical use, the research on renovation and consolidation techniques of damaged pipes gains extensive attention by experts and scholars both at home and abroad. The analysis of mechanical behaviors of reinforced pressure pipelines and further studies focusing on “the critical buckling” and intensity of pressure pipeline failure are conducted in this paper, providing theoretical basis to restressed fiber-strengthened steel pipes. Deformation coordination equations and buckling control equations of steel pipes under the effect of prestress is deduced by using Rayleigh Ritz method, which is an approximation method based on potential energy stationary value theory and minimum potential energy principle. According to the deformation of prestressed steel pipes, the deflection differential equation of prestressed steel pipes is established, and the critical value of buckling under prestress is obtained.

Design of Fresnel Lens-Type Multi-Trapping Acoustic Tweezers

PubMed Central

Tu, You-Lin; Chen, Shih-Jui; Hwang, Yean-Ren

2016-01-01

In this paper, acoustic tweezers which use beam forming performed by a Fresnel zone plate are proposed. The performance has been demonstrated by finite element analysis, including the acoustic intensity, acoustic pressure, acoustic potential energy, gradient force, and particle distribution. The acoustic tweezers use an ultrasound beam produced by a lead zirconate titanate (PZT) transducer operating at 2.4 MHz and 100 Vpeak-to-peak in a water medium. The design of the Fresnel lens (zone plate) is based on air reflection, acoustic impedance matching, and the Fresnel half-wave band (FHWB) theory. This acoustic Fresnel lens can produce gradient force and acoustic potential wells that allow the capture and manipulation of single particles or clusters of particles. Simulation results strongly indicate a good trapping ability, for particles under 150 µm in diameter, in the minimum energy location. This can be useful for cell or microorganism manipulation. PMID:27886050

All the adiabatic bound states of NO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salzgeber, R.F.; Mandelshtam, V.; Schlier, C.

1998-07-01

We calculated all 2967 even and odd bound states of the adiabatic ground state of NO{sub 2}, using a modification of the abthinspinitio potential energy surface of Leonardi {ital et al.} [J. Chem. Phys. {bold 105}, 9051 (1996)]. The calculation was performed by harmonic inversion of the Chebyshev correlation function generated by a DVR Hamiltonian in Radau coordinates. The relative error for the computed eigenenergies (measured from the potential minimum), is 10{sup {minus}4} or better, corresponding to an absolute error of less than about 2.5thinspcm{sup {minus}1}. Near the dissociation threshold the average density of states is about 0.2/cm{sup {minus}1} formore » each symmetry. Statistical analysis of the states shows some interesting structure of the rigidity parameter {Delta}{sub 3} as a function of energy. {copyright} {ital 1998 American Institute of Physics.}« less

Classical Optimal Control for Energy Minimization Based On Diffeomorphic Modulation under Observable-Response-Preserving Homotopy.

PubMed

Soley, Micheline B; Markmann, Andreas; Batista, Victor S

2018-06-12

We introduce the so-called "Classical Optimal Control Optimization" (COCO) method for global energy minimization based on the implementation of the diffeomorphic modulation under observable-response-preserving homotopy (DMORPH) gradient algorithm. A probe particle with time-dependent mass m( t;β) and dipole μ( r, t;β) is evolved classically on the potential energy surface V( r) coupled to an electric field E( t;β), as described by the time-dependent density of states represented on a grid, or otherwise as a linear combination of Gaussians generated by the k-means clustering algorithm. Control parameters β defining m( t;β), μ( r, t;β), and E( t;β) are optimized by following the gradients of the energy with respect to β, adapting them to steer the particle toward the global minimum energy configuration. We find that the resulting COCO algorithm is capable of resolving near-degenerate states separated by large energy barriers and successfully locates the global minima of golf potentials on flat and rugged surfaces, previously explored for testing quantum annealing methodologies and the quantum optimal control optimization (QuOCO) method. Preliminary results show successful energy minimization of multidimensional Lennard-Jones clusters. Beyond the analysis of energy minimization in the specific model systems investigated, we anticipate COCO should be valuable for solving minimization problems in general, including optimization of parameters in applications to machine learning and molecular structure determination.

Effect of Electronic Excitation on Hydrogen Atom Transfer (Tautomerization) Reactions for the DNA Base Adenine

NASA Technical Reports Server (NTRS)

Chaban, Galina M.; Salter, Latasha M.; Kwak, Dochan (Technical Monitor)

2002-01-01

Geometrical structures and energetic properties for four different tautomers of adenine are calculated in this study, using multi-configurational wave functions. Both the ground and the lowest single excited state potential energy surface are studied. The energetic order of the tautomers on the ground state potential surface is 9H less than 7H less than 3H less than 1H, while on the excited state surface this order is found to be different: 3H less than 1H less than 9H less than 7H. Minimum energy reaction paths are obtained for hydrogen atom transfer (9 yields 3 tautomerization) reactions in the ground and the lowest excited electronic state. It is found that the barrier heights and the shapes of the reaction paths are different for the ground and the excited electronic state, suggesting that the probability of such tautomerization reaction is higher on the excited state potential energy surface. The barrier for this reaction in the excited state may become very low in the presence of water or other polar solvent molecules, and therefore such tautomerization reaction may play an important role in the solution phase photochemistry of adenine.

Hamilton's Equations with Euler Parameters for Rigid Body Dynamics Modeling. Chapter 3

NASA Technical Reports Server (NTRS)

Shivarama, Ravishankar; Fahrenthold, Eric P.

2004-01-01

A combination of Euler parameter kinematics and Hamiltonian mechanics provides a rigid body dynamics model well suited for use in strongly nonlinear problems involving arbitrarily large rotations. The model is unconstrained, free of singularities, includes a general potential energy function and a minimum set of momentum variables, and takes an explicit state space form convenient for numerical implementation. The general formulation may be specialized to address particular applications, as illustrated in several three dimensional example problems.

Analytical and numerical analysis of the slope of von Mises planar trusses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalina, M.; Frantík, P.

2016-06-08

In the present paper, there are presented post-critical stress states which will occur at loading by vertical shift of the top joint in the direction downwards. The formation of certain stress states depends on the size of the angle formed by a straight beam of the von Mises planar truss with horizontal plane. Numerical and analytical methods and their problems with finding the angle were described. The numerical solution applies the method of searching for a minimum of potential energy.

Vibrational treatment of the formic acid double minimum case in valence coordinates

NASA Astrophysics Data System (ADS)

Richter, Falk; Carbonnière, P.

2018-02-01

One single full dimensional valence coordinate HCOOH ground state potential energy surface accurate for both cis and trans conformers for all levels up to 6000 cm-1 relative to trans zero point energy has been generated at CCSD(T)-F12a/aug-cc-pVTZ level. The fundamentals and a set of eigenfunctions complete up to about 3120 and 2660 cm-1 for trans- and cis-HCOOH, respectively, have been calculated and assigned using the improved relaxation method of the Heidelberg multi-configuration time-dependent Hartree package and an exact expression for the kinetic energy in valence coordinates generated by the TANA program. The calculated trans fundamental transition frequencies agree with experiment to within 5 cm-1. A few reassignments are suggested. Our results discard any cis trans delocalization effects for vibrational eigenfunctions up to 3640 cm-1 relative to trans zero point energy.

Auger electron and characteristic energy loss spectra for electro-deposited americium-241

NASA Astrophysics Data System (ADS)

Varma, Matesh N.; Baum, John W.

1983-07-01

Auger electron energy spectra for electro-deposited americium-241 on platinum substrate were obtained using a cylindrical mirror analyzer. Characteristic energy loss spectra for this sample were also obtained at primary electron beam energies of 990 and 390 eV. From these measurements PI, PII, and PIII energy levels for americium-241 are determined. Auger electron energies are compared with theoretically calculated values. Minimum detectability under the present condition of sample preparation and equipment was estimated at approximately 1.2×10-8 g/cm2 or 3.9×10-8 Ci/cm2. Minimum detectability for plutonium-239 under similar conditions was estimated at about 7.2×10-10 Ci/cm2.

Simultaneous Wireless Power Transfer and Secure Multicasting in Cooperative Decode-and-Forward Relay Networks.

PubMed

Lee, Jong-Ho; Sohn, Illsoo; Kim, Yong-Hwa

2017-05-16

In this paper, we investigate simultaneous wireless power transfer and secure multicasting via cooperative decode-and-forward (DF) relays in the presence of multiple energy receivers and eavesdroppers. Two scenarios are considered under a total power budget: maximizing the minimum harvested energy among the energy receivers under a multicast secrecy rate constraint; and maximizing the multicast secrecy rate under a minimum harvested energy constraint. For both scenarios, we solve the transmit power allocation and relay beamformer design problems by using semidefinite relaxation and bisection technique. We present numerical results to analyze the energy harvesting and secure multicasting performances in cooperative DF relay networks.

Simultaneous Wireless Power Transfer and Secure Multicasting in Cooperative Decode-and-Forward Relay Networks

PubMed Central

Lee, Jong-Ho; Sohn, Illsoo; Kim, Yong-Hwa

2017-01-01

In this paper, we investigate simultaneous wireless power transfer and secure multicasting via cooperative decode-and-forward (DF) relays in the presence of multiple energy receivers and eavesdroppers. Two scenarios are considered under a total power budget: maximizing the minimum harvested energy among the energy receivers under a multicast secrecy rate constraint; and maximizing the multicast secrecy rate under a minimum harvested energy constraint. For both scenarios, we solve the transmit power allocation and relay beamformer design problems by using semidefinite relaxation and bisection technique. We present numerical results to analyze the energy harvesting and secure multicasting performances in cooperative DF relay networks. PMID:28509841

Feasibility of utilizing small diameter southern pine for biomass in the Virginia Coastal Plain

Treesearch

Nathan C. Hanzelka; M. Chad Bolding; Scott M. Barrett; Jay Sullivan

2016-01-01

New or retrofitted wood-fired energy plants have increased demand for woody biomass in the stateof Virginia. Loblolly pine (Pinus taeda) commonly serves as a feedstock for these energy plants. Pulpwood conventionally requires a minimum diameter of 4 inches diameter at breast height (DBH) for merchantability, whereas a minimum merchantable diameter...

The Effect of Minimum Wage Rates on High School Completion

ERIC Educational Resources Information Center

Warren, John Robert; Hamrock, Caitlin

2010-01-01

Does increasing the minimum wage reduce the high school completion rate? Previous research has suffered from (1. narrow time horizons, (2. potentially inadequate measures of states' high school completion rates, and (3. potentially inadequate measures of minimum wage rates. Overcoming each of these limitations, we analyze the impact of changes in…

Universal scaling of potential energy functions describing intermolecular interactions. II. The halide-water and alkali metal-water interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werhahn, Jasper C.; Akase, Dai; Xantheas, Sotiris S.

2014-08-14

The scaled versions of the newly introduced [S. S. Xantheas and J. C. Werhahn, J. Chem. Phys.141, 064117 (2014)] generalized forms of some popular potential energy functions (PEFs) describing intermolecular interactions – Mie, Lennard-Jones, Morse, and Buckingham exponential-6 – have been used to fit the ab initio relaxed approach paths and fixed approach paths for the halide-water, X -(H 2O), X = F, Cl, Br, I, and alkali metal-water, M +(H 2O), M = Li, Na, K, Rb, Cs, interactions. The generalized forms of those PEFs have an additional parameter with respect to the original forms and produce fits tomore » the ab initio data that are between one and two orders of magnitude better in the χ 2 than the original PEFs. They were found to describe both the long-range, minimum and repulsive wall of the respective potential energy surfaces quite accurately. Overall the 4-parameter extended Morse (eM) and generalized Buckingham exponential-6 (gBe-6) potentials were found to best fit the ab initio data for these two classes of ion-water interactions. Finally, the fitted values of the parameter of the (eM) and (gBe-6) PEFs that control the repulsive wall of the potential correlate remarkably well with the ionic radii of the halide and alkali metal ions.« less

Wind and solar energy resources on the 'Roof of the World'

NASA Astrophysics Data System (ADS)

Zandler, Harald; Morche, Thomas; Samimi, Cyrus

2015-04-01

The Eastern Pamirs of Tajikistan, often referred to as 'Roof of the World', are an arid high mountain plateau characterized by severe energy poverty that may have great potential for renewable energy resources due to the prevailing natural conditions. The lack of energetic infrastructure makes the region a prime target for decentralized integration of wind and solar power. However, up to date no scientific attempt to assess the regional potential of these resources has been carried out. In this context, it is particularly important to evaluate if wind and solar energy are able to provide enough power to generate thermal energy, as other thermal energy carriers are scarce or unavailable and the existing alternative, local harvest of dwarf shrubs, is unsustainable due to the slow regeneration in this environment. Therefore, this study examines the feasibility of using wind and solar energy as thermal energy sources. Financial frame conditions were set on a maximum amount of five million Euros. This sum provides a realistic scenario as it is based on the current budget of the KfW development bank to finance the modernization of the local hydropower plant in the regions only city, Murghab, with about 1500 households. The basis for resource assessment is data of four climate stations, erected for this purpose in 2012, where wind speed, wind direction, global radiation and temperature are measured at a half hourly interval. These measurements confirm the expectation of a large photovoltaic potential and high panel efficiency with up to 84 percent of extraterrestrial radiation reaching the surface and only 16 hours of temperatures above 25°C were measured in two years at the village stations on average. As these observations are only point measurements, radiation data and the ASTER GDEM was used to train a GIS based solar radiation model to spatially extrapolate incoming radiation. With mean validation errors ranging from 5% in July (minimum) to 15% in December (maximum) the extrapolation showed sufficient modeling performance to create the first solar atlas of the Eastern Pamirs. This solar atlas, adapted to optimal panel inclination using 5000 random points, was used to compute expected electricity amounts for two scenarios: one for decentralized small scale implementation and one for a larger scale photovoltaic (PV) power plant. Based on the month with the minimum incoming radiation and the expected energy demand for cooking, the cost for the required infrastructure was assessed. The results showed that an implementation of a PV power plant in Murghab would generate enough power for basic cooking within the estimated budget in winter. In summer the power plant would deliver at least as much energy as the planned hydropower plant if latter would continuously deliver its anticipated peak power. The decentralized scenario for a village with 210 households without existing energy grid resulted in higher investment costs of about 8,000 € per household to meet basic cooking demands in winter. Wind energy potential was assessed based on local wind measurements and an assumed installation of small scale wind turbines. Short time scale comparison of wind and solar resources showed that they mainly occur simultaneously and positive synergy effects are negligible. Furthermore, the financial analysis resulted in significantly higher cost for wind energy even in favorable locations making this resource less important for the region. Our results suggest that solar energy could make a substantial contribution to sustainable energy supply and to alleviate energy poverty and environmental degradation in the Eastern Pamirs of Tajikistan.

Photoinduced intramolecular charge transfer (ICT) reaction in trans-methyl p-(dimethylamino) cinnamate: A combined fluorescence measurement and quantum chemical calculations

NASA Astrophysics Data System (ADS)

Chakraborty, Amrita; Kar, Samiran; Guchhait, Nikhil

2006-01-01

The photophysical behaviour of trans-methyl p-(dimethylamino) cinnamate ( t-MDMAC) donor-acceptor system has been investigated by steady-state absorption and emission spectroscopy and quantum chemical calculations. The molecule t-MDMAC shows an emission from the locally excited state in non-polar solvents. In addition to weak local emission, a strong solvent dependent red shifted fluorescence in polar aprotic solvents is attributed to highly polar intramolecular charge transfer state. However, the formation of hydrogen-bonded clusters with polar protic solvents has been suggested from a linear correlation between the observed red shifted fluorescence band maxima with hydrogen bonding parameters ( α). Calculations by ab initio and density functional theory show that the lone pair electron at nitrogen center is out of plane of the benzene ring in the global minimum ground state structure. In the gas phase, a potential energy surface along the twist coordinate at the donor (-NMe 2) and acceptor (-CH = CHCOOMe) sites shows stabilization of S 1 state and destabilization S 2 and S 0 states. A similar potential energy calculation along the twist coordinate in acetonitrile solvent using non-equilibrium polarized continuum model also shows more stabilization of S 1 state relative to other states and supports solvent dependent red shifted emission properties. In all types of calculations it is found that the nitrogen lone pair is delocalized over the benzene ring in the global minimum ground state and is localized on the nitrogen centre at the 90° twisted configuration. The S 1 energy state stabilization along the twist coordinate at the donor site and localized nitrogen lone pair at the perpendicular configuration support well the observed dual fluorescence in terms of proposed twisted intramolecular charge transfer (TICT) model.

Tunneling splitting in double-proton transfer: direct diagonalization results for porphycene.

PubMed

Smedarchina, Zorka; Siebrand, Willem; Fernández-Ramos, Antonio

2014-11-07

Zero-point and excited level splittings due to double-proton tunneling are calculated for porphycene and the results are compared with experiment. The calculation makes use of a multidimensional imaginary-mode Hamiltonian, diagonalized directly by an effective reduction of its dimensionality. Porphycene has a complex potential energy surface with nine stationary configurations that allow a variety of tunneling paths, many of which include classically accessible regions. A symmetry-based approach is used to show that the zero-point level, although located above the cis minimum, corresponds to concerted tunneling along a direct trans - trans path; a corresponding cis - cis path is predicted at higher energy. This supports the conclusion of a previous paper [Z. Smedarchina, W. Siebrand, and A. Fernández-Ramos, J. Chem. Phys. 127, 174513 (2007)] based on the instanton approach to a model Hamiltonian of correlated double-proton transfer. A multidimensional tunneling Hamiltonian is then generated, based on a double-minimum potential along the coordinate of concerted proton motion, which is newly evaluated at the RI-CC2/cc-pVTZ level of theory. To make it suitable for diagonalization, its dimensionality is reduced by treating fast weakly coupled modes in the adiabatic approximation. This results in a coordinate-dependent mass of tunneling, which is included in a unique Hermitian form into the kinetic energy operator. The reduced Hamiltonian contains three symmetric and one antisymmetric mode coupled to the tunneling mode and is diagonalized by a modified Jacobi-Davidson algorithm implemented in the Jadamilu software for sparse matrices. The results are in satisfactory agreement with the observed splitting of the zero-point level and several vibrational fundamentals after a partial reassignment, imposed by recently derived selection rules. They also agree well with instanton calculations based on the same Hamiltonian.

On the ultraviolet photodissociation of H2Te

NASA Astrophysics Data System (ADS)

Alekseyev, Aleksey B.; Liebermann, Heinz-Peter; Wittig, Curt

2004-11-01

The photodissociation of H2Te through excitation in the first absorption band is investigated by means of multireference spin-orbit configuration interaction (CI) calculations. Bending potentials for low-lying electronic states of H2Te are obtained in C2v symmetry for Te-H distances fixed at the ground state equilibrium value of 3.14a0, as well as for the minimum energy path constrained to R1=R2. Asymmetric cuts of potential energy surfaces for excited states (at R1=3.14a0 and θ=90.3°) are obtained for the first time. It is shown that vibrational structure in the 380-400 nm region of the long wavelength absorption tail is due to transitions to 3A', which has a shallow minimum at large HTe-H separations. Transitions to this state are polarized in the molecular plane, and this state converges to the excited TeH(2Π1/2)+H(2S) limit. These theoretical data are in accord with the selectivity toward TeH(2Π1/2) relative to TeH(2Π3/2) that has been found experimentally for 355 nm H2Te photodissociation. The calculated 3A'←X˜A' transition dipole moment increases rapidly with HTe-H distance; this explains the observation of 3A' vibrational structure for low vibrational levels, despite unfavorable Franck-Condon factors. According to the calculated vertical energies and transition moment data, the maximum in the first absorption band at ≈245 nm is caused by excitation to 4A″, which has predominantly 21A″ (1B1 in C2v symmetry) character.

Optimizing Natural Gas Networks through Dynamic Manifold Theory and a Decentralized Algorithm: Belgium Case Study

NASA Astrophysics Data System (ADS)

Koch, Caleb; Winfrey, Leigh

2014-10-01

Natural Gas is a major energy source in Europe, yet political instabilities have the potential to disrupt access and supply. Energy resilience is an increasingly essential construct and begins with transmission network design. This study proposes a new way of thinking about modelling natural gas flow. Rather than relying on classical economic models, this problem is cast into a time-dependent Hamiltonian dynamics discussion. Traditional Natural Gas constraints, including inelastic demand and maximum/minimum pipe flows, are portrayed as energy functions and built into the dynamics of each pipe flow. Doing so allows the constraints to be built into the dynamics of each pipeline. As time progresses in the model, natural gas flow rates find the minimum energy, thus the optimal gas flow rates. The most important result of this study is using dynamical principles to ensure the output of natural gas at demand nodes remains constant, which is important for country to country natural gas transmission. Another important step in this study is building the dynamics of each flow in a decentralized algorithm format. Decentralized regulation has solved congestion problems for internet data flow, traffic flow, epidemiology, and as demonstrated in this study can solve the problem of Natural Gas congestion. A mathematical description is provided for how decentralized regulation leads to globally optimized network flow. Furthermore, the dynamical principles and decentralized algorithm are applied to a case study of the Fluxys Belgium Natural Gas Network.

Theoretical analysis of the time-resolved binary (e, 2e) binding energy spectra on three-body photodissociation of acetone at 195 nm

NASA Astrophysics Data System (ADS)

Yamazaki, M.; Nakayama, S.; Zhu, C. Y.; Takahashi, M.

2017-11-01

We report on theoretical progress in time-resolved (e, 2e) electron momentum spectroscopy of photodissociation dynamics of the deuterated acetone molecule at 195 nm. We have examined the predicted minimum energy reaction path to investigate whether associated (e, 2e) calculations meet the experimental results. A noticeable difference between the experiment and calculations has been found at around binding energy of 10 eV, suggesting that the observed difference may originate, at least partly, in ever-unconsidered non-minimum energy paths.

Molecular mechanism of direct proflavine-DNA intercalation: evidence for drug-induced minimum base-stacking penalty pathway.

PubMed

Sasikala, Wilbee D; Mukherjee, Arnab

2012-10-11

DNA intercalation, a biophysical process of enormous clinical significance, has surprisingly eluded molecular understanding for several decades. With appropriate configurational restraint (to prevent dissociation) in all-atom metadynamics simulations, we capture the free energy surface of direct intercalation from minor groove-bound state for the first time using an anticancer agent proflavine. Mechanism along the minimum free energy path reveals that intercalation happens through a minimum base stacking penalty pathway where nonstacking parameters (Twist→Slide/Shift) change first, followed by base stacking parameters (Buckle/Roll→Rise). This mechanism defies the natural fluctuation hypothesis and provides molecular evidence for the drug-induced cavity formation hypothesis. The thermodynamic origin of the barrier is found to be a combination of entropy and desolvation energy.

Fe/O ratio behavior as an indicator of solar plasma state at different solar activity manifestations and in periods of their absence

NASA Astrophysics Data System (ADS)

Minasyants, Gennady; Minasyants, Tamara; Tomozov, Vladimir

2018-03-01

We report the results of the investigation into plasma physical characteristics at various solar activity manifestations and in periods of their absence. These results have been obtained from quantitative estimates of the relative abundance of Fe/O ions in different energy ranges. Maximum values of the Fe/O ratio is shown to correspond to particle fluxes from impulsive flares for ions with energies <2 MeV/n (the most significant manifestation of the FIP effect). In particle fluxes from gradual flares, the Fe/O value decreases smoothly with ion energy and is noticeably inferior to values of fluxes in impulsive events. We have established that the properties of flares of solar cosmic rays indicate their belonging to a separate subclass in the total population of gradual events. Relying on variations in the abundance of Fe/O ions, we propose an explanation of the solar plasma behavior during the development of flares of both classes. Magnetic clouds (a separate type of coronal mass ejections (CME)), which have regions of turbulent compression and are sources of strong geomagnetic storms, exhibit a relative composition of Fe ions comparable to the abundance of Fe in ion fluxes from gradual flares. We have found out that the Fe/O value can be used to detect penetration of energetic flare plasma into the CME body at the initial phase of their joint development and to estimate its relative contribution. During solar minimum with the complete absence of sunspots, the Fe/O ratio during periods of "quiet" solar wind show absolutely low values of Fe/O=0.004-0.010 in the energy range from 2-5 to 30 MeV/n. This is associated with the manifestation of the cosmic ray anomalous component, which causes an increase in the intensity of ion fluxes with a high first ionization potential, including oxygen (O), and elements with a low first ionization potential (Fe) demonstrate the weakening of the fluxes. As for particles with higher energies (Ek>30 MeV/n), the Fe/O increase is due to the decisive influence of galactic cosmic rays on the composition of impurity elements in the solar wind under solar minimum conditions. The relative content of heavy elements in galactic cosmic rays 30-500 MeV/n is similar to values in fluxes from gradual flares during high solar activity. During solar minimum without sunspots, the behavior of Fe/O for different ion energy ranges in plasma flows from coronal holes (CH) and in the solar wind exhibits only minor deviations. At the same time, plasma flows associated with the disturbed frontal CH region can be sources of moderate geomagnetic storms.

Dependence of Excited State Potential Energy Surfaces on the Spatial Overlap of the Kohn-Sham Orbitals and the Amount of Nonlocal Hartree-Fock Exchange in Time-Dependent Density Functional Theory.

PubMed

Plötner, Jürgen; Tozer, David J; Dreuw, Andreas

2010-08-10

Time-dependent density functional theory (TDDFT) with standard GGA or hybrid exchange-correlation functionals is not capable of describing the potential energy surface of the S1 state of Pigment Yellow 101 correctly; an additional local minimum is observed at a twisted geometry with substantial charge transfer (CT) character. To investigate the influence of nonlocal exact orbital (Hartree-Fock) exchange on the shape of the potential energy surface of the S1 state in detail, it has been computed along the twisting coordinate employing the standard BP86, B3LYP, and BHLYP xc-functionals as well as the long-range separated (LRS) exchange-correlation (xc)-functionals LC-BOP, ωB97X, ωPBE, and CAM-B3LYP and compared to RI-CC2 benchmark results. Additionally, a recently suggested Λ-parameter has been employed that measures the amount of CT in an excited state by calculating the spatial overlap of the occupied and virtual molecular orbitals involved in the transition. Here, the error in the calculated S1 potential energy curves at BP86, B3LYP, and BHLYP can be clearly related to the Λ-parameter, i.e., to the extent of charge transfer. Additionally, it is demonstrated that the CT problem is largely alleviated when the BHLYP xc-functional is employed, although it still exhibits a weak tendency to underestimate the energy of CT states. The situation improves drastically when LRS-functionals are employed within TDDFT excited state calculations. All tested LRS-functionals give qualitatively the correct potential energy curves of the energetically lowest excited states of P. Y. 101 along the twisting coordinate. While LC-BOP and ωB97X overcorrect the CT problem and now tend to give too large excitation energies compared to other non-CT states, ωPBE and CAM-B3LYP are in excellent agreement with the RI-CC2 results, with respect to both the correct shape of the potential energy curve as well as the absolute values of the calculated excitation energies.

Tantalum-based semiconductors for solar water splitting.

PubMed

Zhang, Peng; Zhang, Jijie; Gong, Jinlong

2014-07-07

Solar energy utilization is one of the most promising solutions for the energy crises. Among all the possible means to make use of solar energy, solar water splitting is remarkable since it can accomplish the conversion of solar energy into chemical energy. The produced hydrogen is clean and sustainable which could be used in various areas. For the past decades, numerous efforts have been put into this research area with many important achievements. Improving the overall efficiency and stability of semiconductor photocatalysts are the research focuses for the solar water splitting. Tantalum-based semiconductors, including tantalum oxide, tantalate and tantalum (oxy)nitride, are among the most important photocatalysts. Tantalum oxide has the band gap energy that is suitable for the overall solar water splitting. The more negative conduction band minimum of tantalum oxide provides photogenerated electrons with higher potential for the hydrogen generation reaction. Tantalates, with tunable compositions, show high activities owning to their layered perovskite structure. (Oxy)nitrides, especially TaON and Ta3N5, have small band gaps to respond to visible-light, whereas they can still realize overall solar water splitting with the proper positions of conduction band minimum and valence band maximum. This review describes recent progress regarding the improvement of photocatalytic activities of tantalum-based semiconductors. Basic concepts and principles of solar water splitting will be discussed in the introduction section, followed by the three main categories regarding to the different types of tantalum-based semiconductors. In each category, synthetic methodologies, influencing factors on the photocatalytic activities, strategies to enhance the efficiencies of photocatalysts and morphology control of tantalum-based materials will be discussed in detail. Future directions to further explore the research area of tantalum-based semiconductors for solar water splitting are also discussed.

Low-Lying Energy Isomers and Global Minima of Aqueous Nanoclusters: Structures and Spectroscopic Features of the Pentagonal Dodecahedron (H2O)20 and (H3O)+(H2O)20

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xantheas, Sotiris S.

We rely on a hierarchy of methods to identify the low-lying isomers for the pentagonal dodecahedron (H2O)20 and the H3O+(H2O)20 clusters. Initial screening of isomers was performed with classical potentials [TIP4P, TTM2-F, TTM2.1-F for (H2O)20 and ASP for H3O+(H2O)20] and the networks obtained with those potentials were subsequently reoptimized at the DFT (B3LYP) and MP2 levels of theory. For the pentagonal dodecahedron (H2O)20 it was found that DFT (B3LYP) and MP2 produced the same global minimum. However, this was not the case for the H3O+(H2O)20 cluster, for which MP2 produced a different network for the global minimum when compared tomore » DFT (B3LYP). All low-lying minima of H3O+(H2O)20 correspond to hydrogen bonding networks having 9 ''free'' OH bonds and the hydronium ion on the surface of the cluster. The fact that DFT (B3LYP) and MP2 produce different results and issues related to the use of a smaller basis set, explains the discrepancy between the current results and the structure previously suggested [Science 304, 1137 (2004)] for the global minimum of the H3O+(H2O)20 cluster. Additionally, the IR spectra of the MP2 global minimum are closer to the experimentally measured ones than the spectra of the previously suggested DFT global minimum. The latter exhibit additional bands in the most red-shifted region of the OH stretching vibrations (corresponding to the ''fingerprint'' of the underlying hydrogen bonding network), which are absent from both the experimental as well as the spectra of the new structure suggested for the global minimum of this cluster.« less

Estimation of Leakage Potential of Selected Sites in Interstate and Tri-State Canals Using Geostatistical Analysis of Selected Capacitively Coupled Resistivity Profiles, Western Nebraska, 2004

USGS Publications Warehouse

Vrabel, Joseph; Teeple, Andrew; Kress, Wade H.

2009-01-01

With increasing demands for reliable water supplies and availability estimates, groundwater flow models often are developed to enhance understanding of surface-water and groundwater systems. Specific hydraulic variables must be known or calibrated for the groundwater-flow model to accurately simulate current or future conditions. Surface geophysical surveys, along with selected test-hole information, can provide an integrated framework for quantifying hydrogeologic conditions within a defined area. In 2004, the U.S. Geological Survey, in cooperation with the North Platte Natural Resources District, performed a surface geophysical survey using a capacitively coupled resistivity technique to map the lithology within the top 8 meters of the near-surface for 110 kilometers of the Interstate and Tri-State Canals in western Nebraska and eastern Wyoming. Assuming that leakage between the surface-water and groundwater systems is affected primarily by the sediment directly underlying the canal bed, leakage potential was estimated from the simple vertical mean of inverse-model resistivity values for depth levels with geometrically increasing layer thickness with depth which resulted in mean-resistivity values biased towards the surface. This method generally produced reliable results, but an improved analysis method was needed to account for situations where confining units, composed of less permeable material, underlie units with greater permeability. In this report, prepared by the U.S. Geological Survey in cooperation with the North Platte Natural Resources District, the authors use geostatistical analysis to develop the minimum-unadjusted method to compute a relative leakage potential based on the minimum resistivity value in a vertical column of the resistivity model. The minimum-unadjusted method considers the effects of homogeneous confining units. The minimum-adjusted method also is developed to incorporate the effect of local lithologic heterogeneity on water transmission. Seven sites with differing geologic contexts were selected following review of the capacitively coupled resistivity data collected in 2004. A reevaluation of these sites using the mean, minimum-unadjusted, and minimum-adjusted methods was performed to compare the different approaches for estimating leakage potential. Five of the seven sites contained underlying confining units, for which the minimum-unadjusted and minimum-adjusted methods accounted for the confining-unit effect. Estimates of overall leakage potential were lower for the minimum-unadjusted and minimum-adjusted methods than those estimated by the mean method. For most sites, the local heterogeneity adjustment procedure of the minimum-adjusted method resulted in slightly larger overall leakage-potential estimates. In contrast to the mean method, the two minimum-based methods allowed the least permeable areas to control the overall vertical permeability of the subsurface. The minimum-adjusted method refined leakage-potential estimation by additionally including local lithologic heterogeneity effects.

Topology Trivialization and Large Deviations for the Minimum in the Simplest Random Optimization

NASA Astrophysics Data System (ADS)

Fyodorov, Yan V.; Le Doussal, Pierre

2014-01-01

Finding the global minimum of a cost function given by the sum of a quadratic and a linear form in N real variables over (N-1)-dimensional sphere is one of the simplest, yet paradigmatic problems in Optimization Theory known as the "trust region subproblem" or "constraint least square problem". When both terms in the cost function are random this amounts to studying the ground state energy of the simplest spherical spin glass in a random magnetic field. We first identify and study two distinct large-N scaling regimes in which the linear term (magnetic field) leads to a gradual topology trivialization, i.e. reduction in the total number {N}_{tot} of critical (stationary) points in the cost function landscape. In the first regime {N}_{tot} remains of the order N and the cost function (energy) has generically two almost degenerate minima with the Tracy-Widom (TW) statistics. In the second regime the number of critical points is of the order of unity with a finite probability for a single minimum. In that case the mean total number of extrema (minima and maxima) of the cost function is given by the Laplace transform of the TW density, and the distribution of the global minimum energy is expected to take a universal scaling form generalizing the TW law. Though the full form of that distribution is not yet known to us, one of its far tails can be inferred from the large deviation theory for the global minimum. In the rest of the paper we show how to use the replica method to obtain the probability density of the minimum energy in the large-deviation approximation by finding both the rate function and the leading pre-exponential factor.

Evaluating the DLVO Model for Non-Aqueous Colloidal Suspensions

NASA Astrophysics Data System (ADS)

DeCarlo, Keith Joseph

Application of DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory for suspensions utilizing non-aqueous suspension mediums has been tested. Prediction of suspension stability using DLVO theory requires the calculation of the attractive and repulsive forces between the suspended colloids and that the only significant stabilization mechanism present is electrostatic stabilization which was tested. The van der Waals attractive potential was calculated for 12 different colloids in 11 suspending mediums in accord with Lifshitz's treatment and a new approximation proposing that the material bandgap energy can be used to approximate the Hamaker constant was developed. This treatment requires the complete knowledge of the permittivity as a function of frequency for all the components in the respective suspension. The permittivity data was simplified using a damped oscillator model described by Ninham and Parsegian. All permittivity data was compiled from the literature. Microwave data was tabulated by NIST, infrared parameters were determined from FTIR data, and the ultraviolet/visual parameters were determined via Cauchy plots or estimated by the bandgap. Using the bandgap to approximate the ultraviolet/visual parameters proved to be more accurate than other approximations when compared to the accepted values. It was found that the non-oxide and non-stoichiometric colloids tested had the largest associated van der Waals attractive force. The van der Waals potential calculated for oxide particles was found to follow a direct relationship with the ionic character of the bonding. Repulsive forces were calculated for 12 different colloids in 11 suspending mediums. The calculated repulsive potential generated is a function of both the magnitude of charge generated on each colloid (zeta-potential) and the size of the interacting double-layers. zeta-potential was measured for each suspension using a microelectrophoretic technique and the double-layer thickness was calculated. It was demonstrated that as the polarity of the suspending medium increased, the thickness of the double-layer also increased. A large double-layer thickness was found to directly correlate to the suspension stability. A large double-layer thickness results in a decreased slope of the charge degradation from the colloidal surface to the bulk suspension. This coupled with a large magnitude of surface charge increases the probability of dispersion. Through viscosity measurements, the stability mechanism of each suspension was determined by comparison of the viscosity at a shear rate of 1.0s -1 with the shear thinning exponent. It was determined that, of the suspension mediums tested, heptane, octanoic acid, and poly(ethylene glycol) introduce non-electrostatic stabilization mechanisms significant enough to invalidate the DLVO predictions for suspensions made using those mediums. Consistent with DLVO theory, the total interaction potential was calculated by summation of the repulsive and attractive potentials of each suspension (84 suspensions total) as a function of separation distance. Based upon the results of the summation, the suspension stability can be predicted. 64 of the 84 suspensions were determined to be unstable as the colloids agglomerated in the primary minimum, 11 suspensions were determined to be weakly flocculated, and nine suspensions were found to be stable. Viscosity was used to determine the critical value for the thermal energy barrier and to test the DLVO predictions. The critical value of the thermal energy barrier was found to be 2.0 x 10 -6J/m2. Therefore, for suspensions calculated to have a thermal energy barrier less than the critical value, the Brownian motion of the colloids in suspension at 298K were enough to overcome it, resulting in agglomeration at the primary minimum. For suspensions with a thermal barrier larger than 2.0 x 10-6J/m2, the interacting colloids moved into the secondary energy minimum. All suspensions tested in which the thermal energy barrier was less than 2.0 x 10-6J/m 2 had a specific viscosity at a shear rate of 1.0s-1 greater than the cut-off viscosity for stability. If the colloids moved into the secondary minimum, the resulting suspension was characterized as either being weakly flocculated or stable. Weakly flocculated suspensions had an equilibrium separation distance of colloids less than 40nm resulting in a viscosity at a shear rate of 1.0s-1 larger than the determined specific viscosity cut-off (1.1x 104), but a shear thinning exponent greater than 1.0. Stable suspensions were defined by the colloids as having an equilibrium separation distance greater than 40nm, resulting in viscosity values at a shear rate of 1.0s-1 smaller than that of the determined cut-off viscosity value.

Design for minimum energy in interstellar communication

NASA Astrophysics Data System (ADS)

Messerschmitt, David G.

2015-02-01

Microwave digital communication at interstellar distances is the foundation of extraterrestrial civilization (SETI and METI) communication of information-bearing signals. Large distances demand large transmitted power and/or large antennas, while the propagation is transparent over a wide bandwidth. Recognizing a fundamental tradeoff, reduced energy delivered to the receiver at the expense of wide bandwidth (the opposite of terrestrial objectives) is advantageous. Wide bandwidth also results in simpler design and implementation, allowing circumvention of dispersion and scattering arising in the interstellar medium and motion effects and obviating any related processing. The minimum energy delivered to the receiver per bit of information is determined by cosmic microwave background alone. By mapping a single bit onto a carrier burst, the Morse code invented for the telegraph in 1836 comes closer to this minimum energy than approaches used in modern terrestrial radio. Rather than the terrestrial approach of adding phases and amplitudes increases information capacity while minimizing bandwidth, adding multiple time-frequency locations for carrier bursts increases capacity while minimizing energy per information bit. The resulting location code is simple and yet can approach the minimum energy as bandwidth is expanded. It is consistent with easy discovery, since carrier bursts are energetic and straightforward modifications to post-detection pattern recognition can identify burst patterns. Time and frequency coherence constraints leading to simple signal discovery are addressed, and observations of the interstellar medium by transmitter and receiver constrain the burst parameters and limit the search scope.

On the electrodynamics of moving particles in a quasi flat spacetime with Lorentz violation and its cosmological implications

NASA Astrophysics Data System (ADS)

Cruz, Cláudio Nassif

2016-06-01

This research aims to develop a new approach towards a consistent coupling of electromagnetic and gravitational fields, by using an electron that couples with a weak gravitational potential by means of its electromagnetic field. To accomplish this, we must first build a new model which provides the electromagnetic nature of both the mass and the energy of the electron, and which is implemented with the idea of γ-photon decay into an electron-positron pair. After this, we place the electron (or positron) in the presence of a weak gravitational potential given in the intergalactic medium, so that its electromagnetic field undergoes a very small perturbation, thus leading to a slight increase in the field’s electromagnetic energy density. This perturbation takes place by means of a tiny coupling constant ξ because gravity is a very weak interaction compared with the electromagnetic one. Thus, we realize that ξ is a new dimensionless universal constant, which reminds us of the fine structure constant α; however, ξ is much smaller than α because ξ takes into account gravity, i.e. ξ ∝G. We find ξ = V/c≅1.5302 × 10-22, where c is the speed of light and V ∝G(≅4.5876 × 10-14m/s) is a universal minimum speed that represents the lowest limit of speed for any particle. Such a minimum speed, unattainable by particles, represents a preferred reference frame associated with a background field that breaks the Lorentz symmetry. The metric of the flat spacetime shall include the presence of a uniform vacuum energy density, which leads to a negative pressure at cosmological scales (cosmological anti-gravity). The tiny values of the cosmological constant and the vacuum energy density will be successfully obtained in agreement with the observational data.

Solar-Cycle Variability of Magnetosheath Fluctuations at Earth and Venus

NASA Astrophysics Data System (ADS)

Dwivedi, N. K.; Narita, Y.; Kovacs, P.

2014-12-01

The magnetosheath is a region between the bow-shock and magnetopause and the magnetosheath plasma is mostly in the turbulent state. In the present investigation we put an effort to closely examine the magnetosheath fluctuations dependency on the solar-cycles (solar-maximum and solar minimum) at the magnetized planetary body (Earth) and their comparison with the un-magnetized planetary body (Venus) for the solar minimum. We use the CLUSTER FGM data for the solar-maximum (2001-2002), solar-minimum (2006-2008) and Venus fluxgate magnetometer data for the solar-minimum (2006-2008) to perform a comparative statistical study on the energy spectra and probability density function (PDF) and asses the spectral features of the magnetic fluctuations of the both planetary bodies. In the comparison we study the relation between the inertial ranges of the spectra and the temporal scales of non-Gaussian magnetic fluctuations derived from PDF analyses. The first can refer to turbulent cascade dynamics, while the latter may indicate intermittency. We first transformed the magnetic field data into mean field aligned coordinate system with respect to the large-scale magnetic field direction and then after we compute the power spectral density with the help of Welch algorithm. The computed energy spectra of Earth's magnetosheath show a moderate variability with the solar-cycles and have a broader inertial range. However the estimated energy spectra for the solar-minimum at Venus give the clear evidence of the existence of the break point in the vicinity of the ion gyroradius. After the break-point the energy spectra become steeper and show a distinctive spectral scales which is interpreted as the realization of the begging of the energy cascade. We also briefly address the influence of turbulence on the plasma transport and wave dynamics responsible for the spectral break and predict spectral features of the energy spectra for the solar-maximum at Venus based on the results obtained for the solar-minimum. The research leading to these results has received funding from the European Community's Seventh Framework Programme ([FP7/2007-2013]) under grant agreement number 313038/STORM.

Considerations for NSLS-II Synchrotron Radiation Protection When Operating Damping Wigglers at Low Machine Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seletskiy, S.; Podobedov, B.

2015-12-30

The NSLS-II storage ring vacuum chamber, including frontends (FE) and beamlines (BL), is protected from possible damage from synchrotron radiation (SR) emitted from insertion devices (IDs) by a dedicated active interlock system (AIS). The system monitors electron beam position and angle and triggers a beam dump if the beam orbit is outside of the active interlock envelope (AIE). The AIE was calculated under the assumptions of 3 GeV beam energy and ID gaps set to their minimum operating values (i.e. “fully closed”). Recently it was proposed to perform machine studies that would ramp the stored beam energy significantly below themore » nominal operational value of 3 GeV. These studies may potentially include the use of NSLS-II damping wigglers (DWs) for electron beam emittance reduction and control.« less

An Energy-Efficient Compressive Image Coding for Green Internet of Things (IoT).

PubMed

Li, Ran; Duan, Xiaomeng; Li, Xu; He, Wei; Li, Yanling

2018-04-17

Aimed at a low-energy consumption of Green Internet of Things (IoT), this paper presents an energy-efficient compressive image coding scheme, which provides compressive encoder and real-time decoder according to Compressive Sensing (CS) theory. The compressive encoder adaptively measures each image block based on the block-based gradient field, which models the distribution of block sparse degree, and the real-time decoder linearly reconstructs each image block through a projection matrix, which is learned by Minimum Mean Square Error (MMSE) criterion. Both the encoder and decoder have a low computational complexity, so that they only consume a small amount of energy. Experimental results show that the proposed scheme not only has a low encoding and decoding complexity when compared with traditional methods, but it also provides good objective and subjective reconstruction qualities. In particular, it presents better time-distortion performance than JPEG. Therefore, the proposed compressive image coding is a potential energy-efficient scheme for Green IoT.

Energy sources of polycyclic aromatic hydrocarbons. [Carcinogenicity of PAHs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerin, M. R.

1977-01-01

Combustion is the predominant end-process by which fossil fuels are converted to energy. Combustion, particularly when inefficient, is also the primary technological source of polycyclic aromatic hydrocarbons (PAHs) released into the environment. The need for liquid fuels to supply the transportation industry and for nonpolluting fuels for heat and power generation provide the incentive to commercialize processes to convert coal to substitute natural gas and oil. These processes represent a potentially massive new source of environmental PAHs. Insuring an adequate supply of energy with minimum impact on the environment and on health is one of the most important, urgent, andmore » challenging goals currently facing science and technology. Polycyclic aromatic hydrocarbon related carcinogenesis is among the most important of possible occupational- and environmental-health impacts of much of the current and projected national energy base. An understanding of the relationship of polycyclic aromatic hydrocarbons (PAHs) to human cancer and a continued surveillance of energy sources for PAH content are necessary to minimize this impact.« less

Surface energy effect on nonlinear buckling and postbuckling behavior of functionally graded piezoelectric cylindrical nanoshells under lateral pressure

NASA Astrophysics Data System (ADS)

Fang, Xue-Qian; Zhu, Chang-Song; Liu, Jin-Xi; Zhao, Jing

2018-04-01

In this paper, the surface energy effect on the nonlinear buckling and postbuckling behavior of functionally graded piezoelectric (FGP) cylindrical nanoshells subjected to lateral pressure is studied based on the electro-elastic surface/interface theory together with von-Kármán-Donnell-type kinematics of nonlinearity. The total strain energy of the FGP nanoshell, including surface energy, is derived by considering the constitutive formulations of surface phase. The principle of minimum potential energy is utilized to establish the nonlinear governing differential equations, and the singular perturbation technique is employed to obtain the asymptotic solutions. Then, two sets of comparison are conducted to validate the present work, and some numerical examples are given to study the effects of surface parameters, power law index and aspect ratio on the buckling and postbuckling behavior of FGP nanoshells. The results show that the critical buckling load and postbuckling path of FGP nanoshell are significantly size-dependent.

Guiding Conformation Space Search with an All-Atom Energy Potential

PubMed Central

Brunette, TJ; Brock, Oliver

2009-01-01

The most significant impediment for protein structure prediction is the inadequacy of conformation space search. Conformation space is too large and the energy landscape too rugged for existing search methods to consistently find near-optimal minima. To alleviate this problem, we present model-based search, a novel conformation space search method. Model-based search uses highly accurate information obtained during search to build an approximate, partial model of the energy landscape. Model-based search aggregates information in the model as it progresses, and in turn uses this information to guide exploration towards regions most likely to contain a near-optimal minimum. We validate our method by predicting the structure of 32 proteins, ranging in length from 49 to 213 amino acids. Our results demonstrate that model-based search is more effective at finding low-energy conformations in high-dimensional conformation spaces than existing search methods. The reduction in energy translates into structure predictions of increased accuracy. PMID:18536015

The Optical Flow Technique on the Research of Solar Non-potentiality

NASA Astrophysics Data System (ADS)

Liu, Ji-hong; Zhang, Hong-qi

2010-06-01

Several optical flow techniques, which have being applied to the researches of solar magnetic non-potentiality recently, have been summarized here. And a few new non-potential parameters which can be derived from them have been discussed, too. The main components of the work are presented as follows: (1) The optical flow techniques refers to a series of new image analyzing techniques arisen recently on the researches of solar magnetic non-potentiality. They mainly include LCT (local correlation tracking), ILCT (inductive equation combining with LCT), MEF (minimum energy effect), DAVE (differential affine velocity estimator) and NAVE (nonlinear affine velocity estimator). Their calculating and applying conditions, merits and deficiencies, all have been discussed detailedly in this work. (2) Benefit from the optical flow techniques, the transverse velocity fields of the magnetic features on the solar surface may be determined by a time sequence of high-quality images currently produced by high-resolution observations either from the ground or in space. Consequently, several new non-potential parameters may be acquired, such as the magnetic helicity flux, the induced electric field in the photosphere, the non-potential magnetic stress (whose area integration is the Lorentz force), etc. Then we can determine the energy flux across the photosphere, and subsequently evaluate the energy budget. Former works on them by small or special samples have shown that they are probably related closely to the erupting events, such as flare, filament eruptions and coronal mass ejections.

Characterization and biodegradability of sludge from a high rate A-stage contact tank and B-stage membrane bioreactor of a pilot-scale AB system treating municipal wastewaters.

PubMed

Trzcinski, Antoine Prandota; Ganda, Lily; Kunacheva, Chinagarn; Zhang, Dong Qing; Lin, Li Leonard; Tao, Guihe; Lee, Yingjie; Ng, Wun Jern

2016-10-01

In light of global warming mitigation efforts, increasing sludge disposal costs, and need for reduction in the carbon footprint of wastewater treatment plants, innovation in treatment technology has been tailored towards energy self-sufficiency. The AB process is a promising technology for achieving maximal energy recovery from wastewaters with minimum energy expenditure and therefore inherently reducing excess sludge production. Characterization of this novel sludge and its comparison with the more conventional B-stage sludge are necessary for a deeper understanding of AB treatment process design. This paper presents a case study of a pilot-scale AB system treating municipal wastewaters as well as a bio- (biochemical methane potential and adenosine tri-phosphate analysis) and physico-chemical properties (chemical oxygen demand, sludge volume index, dewaterability, calorific value, zeta potential and particle size distribution) comparison of the organic-rich A-stage against the B-stage activated sludge. Compared to the B-sludge, the A-sludge yielded 1.4 to 4.9 times more methane throughout the 62-week operation.

How Extreme is TRAPPIST-1? A look into the planetary system’s extreme-UV radiation environment

NASA Astrophysics Data System (ADS)

Peacock, Sarah; Barman, Travis; Shkolnik, Evgenya L.

2018-01-01

The ultracool dwarf star TRAPPIST-1 hosts three earth-sized planets at orbital distances where water has the potential to exist in liquid form on the planets’ surface. Close-in exoplanets, such as these, become vulnerable to water loss as stellar XUV radiation heats and expands their upper atmospheres. Currently, little is known about the high-energy radiation environment around TRAPPIST-1. Recent efforts to quantify the XUV radiation rely on empirical relationships based on X-ray or Lyman alpha line observations and yield very different results. The scaling relations used between the X-ray and EUV emission result in high-energy irradiation of the planets 10-1000x greater than present day Earth, stripping atmospheres and oceans in 1 Gyr, while EUV estimated from Lyman alpha flux is much lower. Here we present upper-atmosphere PHOENIX models representing the minimum and maximum potential EUV stellar flux from TRAPPIST-1. We use GALEX FUV and NUV photometry for similar aged M stars to determine the UV flux extrema in an effort to better constrain the high-energy radiation environment around TRAPPIST-1.

A new ab initio potential energy surface of LiClH (1A') system and quantum dynamics calculation for Li + HCl (v = 0, j = 0-2) → LiCl + H reaction

NASA Astrophysics Data System (ADS)

Tan, Rui Shan; Zhai, Huan Chen; Yan, Wei; Gao, Feng; Lin, Shi Ying

2017-04-01

A new ab initio potential energy surface (PES) for the ground state of Li + HCl reactive system has been constructed by three-dimensional cubic spline interpolation of 36 654 ab initio points computed at the MRCI+Q/aug-cc-pV5Z level of theory. The title reaction is found to be exothermic by 5.63 kcal/mol (9 kcal/mol with zero point energy corrections), which is very close to the experimental data. The barrier height, which is 2.99 kcal/mol (0.93 kcal/mol for the vibrationally adiabatic barrier height), and the depth of van der Waals minimum located near the entrance channel are also in excellent agreement with the experimental findings. This study also identified two more van der Waals minima. The integral cross sections, rate constants, and their dependence on initial rotational states are calculated using an exact quantum wave packet method on the new PES. They are also in excellent agreement with the experimental measurements.

On the importance of full-dimensionality in low-energy molecular scattering calculations

PubMed Central

Faure, Alexandre; Jankowski, Piotr; Stoecklin, Thierry; Szalewicz, Krzysztof

2016-01-01

Scattering of H2 on CO is of great importance in astrophysics and also is a benchmark system for comparing theory to experiment. We present here a new 6-dimensional potential energy surface for the ground electronic state of H2-CO with an estimated uncertainty of about 0.6 cm−1 in the global minimum region, several times smaller than achieved earlier. This potential has been used in nearly exact 6-dimensional quantum scattering calculations to compute state-to-state cross-sections measured in low-energy crossed-beam experiments. Excellent agreement between theory and experiment has been achieved in all cases. We also show that the fully 6-dimensional approach is not needed with the current accuracy of experimental data since an equally good agreement with experiment was obtained using only a 4-dimensional treatment, which validates the rigid-rotor approach widely used in scattering calculations. This finding, which disagrees with some literature statements, is important since for larger systems full-dimensional scattering calculations are currently not possible. PMID:27333870

Airy structure in 16O+14C nuclear rainbow scattering

NASA Astrophysics Data System (ADS)

Ohkubo, S.; Hirabayashi, Y.

2015-08-01

The Airy structure in 16 O +14 C rainbow scattering is studied with an extended double-folding (EDF) model that describes all the diagonal and off-diagonal coupling potentials derived from the microscopic realistic wave functions for 16 O by using a density-dependent nucleon-nucleon force. The experimental angular distributions at EL=132 , 281, and 382.2 MeV are well reproduced by the calculations. By studying the energy evolution of the Airy structure, the Airy minimum around θ =76∘ in the angular distribution at EL=132 MeV is assigned as the second-order Airy minimum A 2 in contrast to the recent literature which assigns it as the third order A 3 . The Airy minima in the 90∘ excitation function is investigated in comparison with well-known 16 O +16 O and 12 C +12 C systems. Evolution of the Airy structure into the molecular resonances with the 16 O +14 C cluster structure in the low-energy region around Ec .m .=30 MeV is discussed. It is predicted theoretically for the first time for a non-4 N 16O +14 C system that Airy elephants in the 90∘ excitation function are present.

Photodissociation Dynamics of Phenol: Multistate Trajectory Simulations including Tunneling

DOE PAGES

Xu, Xuefei; Zheng, Jingjing; Yang, Ke R.; ...

2014-10-27

We report multistate trajectory simulations, including coherence, decoherence, and multidimensional tunneling, of phenol photodissociation dynamics. The calculations are based on full-dimensional anchor-points reactive potential surfaces and state couplings fit to electronic structure calculations including dynamical correlation with an augmented correlation-consistent polarized valence double-ζ basis set. The calculations successfully reproduce the experimentally observed bimodal character of the total kinetic energy release spectra and confirm the interpretation of the most recent experiments that the photodissociation process is dominated by tunneling. Analysis of the trajectories uncovers an unexpected dissociation pathway for one quantum excitation of the O–H stretching mode of the S 1more » state, namely, tunneling in a coherent mixture of states starting in a smaller R OH (~0.9–1.0 Å) region than has previously been invoked. The simulations also show that most trajectories do not pass close to the S 1–S 2 conical intersection (they have a minimum gap greater than 0.6 eV), they provide statistics on the out-of-plane angles at the locations of the minimum energy adiabatic gap, and they reveal information about which vibrational modes are most highly activated in the products.« less

Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Huixian; School of Physics, Northwest University, Xi’an, Shaanxi 710069; Li, Anyang

2014-12-28

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S{sub 0}) electronic state has been constructed by fitting ∼37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm{sup −1}. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies upmore » to 12 700 cm{sup −1} above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.« less

A canonical stability-elasticity relationship verified for one million face-centred-cubic structures.

PubMed

Maisel, Sascha B; Höfler, Michaela; Müller, Stefan

2012-11-29

Any thermodynamically stable or metastable phase corresponds to a local minimum of a potentially very complicated energy landscape. But however complex the crystal might be, this energy landscape is of parabolic shape near its minima. Roughly speaking, the depth of this energy well with respect to some reference level determines the thermodynamic stability of the system, and the steepness of the parabola near its minimum determines the system's elastic properties. Although changing alloying elements and their concentrations in a given material to enhance certain properties dates back to the Bronze Age, the systematic search for desirable properties in metastable atomic configurations at a fixed stoichiometry is a very recent tool in materials design. Here we demonstrate, using first-principles studies of four binary alloy systems, that the elastic properties of face-centred-cubic intermetallic compounds obey certain rules. We reach two conclusions based on calculations on a huge subset of the face-centred-cubic configuration space. First, the stiffness and the heat of formation are negatively correlated with a nearly constant Spearman correlation for all concentrations. Second, the averaged stiffness of metastable configurations at a fixed concentration decays linearly with their distance to the ground-state line (the phase diagram of an alloy at zero Kelvin). We hope that our methods will help to simplify the quest for new materials with optimal properties from the vast configuration space available.

How Methylation Modifies the Photophysics of the Native All- trans-Retinal Protonated Schiff Base: A CASPT2/MD Study in Gas Phase and in Methanol.

PubMed

Barata-Morgado, Rute; Sánchez, M Luz; Muñoz-Losa, Aurora; Martín, M Elena; Olivares Del Valle, Francisco J; Aguilar, Manuel A

2018-03-22

A comparison between the free-energy surfaces of the all- trans-retinal protonated Schiff base (RPSB) and its 10-methylated derivative in gas phase and methanol solution is performed at CASSCF//CASSCF and CASPT2//CASSCF levels. Solvent effects were included using the average solvent electrostatic potential from molecular dynamics method. This is a QM/MM (quantum mechanics/molecular mechanics) method that makes use of the mean field approximation. It is found that the methyl group bonded to C10 produces noticeable changes in the solution free-energy profile of the S 1 excited state, mainly in the relative stability of the minimum energy conical intersections (MECIs) with respect to the Franck-Condon (FC) point. The conical intersections yielding the 9- cis and 11- cis isomers are stabilized while that yielding the 13- cis isomer is destabilized; in fact, it becomes inaccessible by excitation to S 1 . Furthermore, the planar S 1 minimum is not present in the methylated compound. The solvent notably stabilizes the S 2 excited state at the FC geometry. Therefore, if the S 2 state has an effect on the photoisomerization dynamics, it must be because it permits the RPSB population to branch around the FC point. All these changes combine to speed up the photoisomerization in the 10-methylated compound with respect to the native compound.

Current-Sheet Formation and Reconnection at a Magnetic X Line in Particle-in-Cell Simulations

NASA Technical Reports Server (NTRS)

Black, C.; Antiochos, S. K.; Hesse, M.; Karpen, J. T.; Kuznetsova, M. M.; Zenitani, S.

2011-01-01

The integration of kinetic effects into macroscopic numerical models is currently of great interest to the heliophysics community, particularly in the context of magnetic reconnection. Reconnection governs the large-scale energy release and topological rearrangement of magnetic fields in a wide variety of laboratory, heliophysical, and astrophysical systems. We are examining the formation and reconnection of current sheets in a simple, two-dimensional X-line configuration using high-resolution particle-in-cell (PIC) simulations. The initial minimum-energy, potential magnetic field is perturbed by excess thermal pressure introduced into the particle distribution function far from the X line. Subsequently, the relaxation of this added stress leads self-consistently to the development of a current sheet that reconnects for imposed stress of sufficient strength. We compare the time-dependent evolution and final state of our PIC simulations with macroscopic magnetohydrodynamic simulations assuming both uniform and localized electrical resistivities (C. R. DeVore et al., this meeting), as well as with force-free magnetic-field equilibria in which the amount of reconnection across the X line can be constrained to be zero (ideal evolution) or optimal (minimum final magnetic energy). We will discuss implications of our results for understanding magnetic-reconnection onset and cessation at kinetic scales in dynamically formed current sheets, such as those occurring in the solar corona and terrestrial magnetotail.

Structure of the effective potential for a spherical wormhole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montelongo Garcia, N.; Zannias, T.

2008-09-15

The structure of the effective potential V describing causal geodesics near the throat of an arbitrary spherical wormhole is analyzed. Einstein's equations relative to a set of regular coordinates covering a vicinity of the throat imply that any spherical wormhole can be constructed from solutions of an effective initial value problem with the throat serving as an initial value surface. The initial data involve matter variables, the area A(0) of the throat, and the gradient {lambda}(0) of the redshift factor on the throat. Whenever {lambda}(0)=0, the effective potential V has a critical point on the throat. Conditions upon the datamore » are derived ensuring that the critical point is a local minimum (respectively maximum). For particular families of quasi-Schwarzschild wormholes, V exhibits a local minimum on the throat independently upon the energy E and angular momentum L{sup 2} of the test particles and thus such wormholes admit stable circular timelike and null geodesics on the throat. For families of Chaplygin wormholes, we show that such geodesics are unstable. Based on a suitable power series representation of the metric, properties of V away from the throat are obtained that are useful for the analysis of accretion disks and radiation processes near the throat of any spherical wormhole.« less

Global minimum profile error (GMPE) - a least-squares-based approach for extracting macroscopic rate coefficients for complex gas-phase chemical reactions.

PubMed

Duong, Minh V; Nguyen, Hieu T; Mai, Tam V-T; Huynh, Lam K

2018-01-03

Master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) has shown to be a powerful framework for modeling kinetic and dynamic behaviors of a complex gas-phase chemical system on a complicated multiple-species and multiple-channel potential energy surface (PES) for a wide range of temperatures and pressures. Derived from the ME time-resolved species profiles, the macroscopic or phenomenological rate coefficients are essential for many reaction engineering applications including those in combustion and atmospheric chemistry. Therefore, in this study, a least-squares-based approach named Global Minimum Profile Error (GMPE) was proposed and implemented in the MultiSpecies-MultiChannel (MSMC) code (Int. J. Chem. Kinet., 2015, 47, 564) to extract macroscopic rate coefficients for such a complicated system. The capability and limitations of the new approach were discussed in several well-defined test cases.

Minimum energy information fusion in sensor networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapline, G

1999-05-11

In this paper we consider how to organize the sharing of information in a distributed network of sensors and data processors so as to provide explanations for sensor readings with minimal expenditure of energy. We point out that the Minimum Description Length principle provides an approach to information fusion that is more naturally suited to energy minimization than traditional Bayesian approaches. In addition we show that for networks consisting of a large number of identical sensors Kohonen self-organization provides an exact solution to the problem of combing the sensor outputs into minimal description length explanations.

Fully invariant wavelet enhanced minimum average correlation energy filter for object recognition in cluttered and occluded environments

NASA Astrophysics Data System (ADS)

Tehsin, Sara; Rehman, Saad; Riaz, Farhan; Saeed, Omer; Hassan, Ali; Khan, Muazzam; Alam, Muhammad S.

2017-05-01

A fully invariant system helps in resolving difficulties in object detection when camera or object orientation and position are unknown. In this paper, the proposed correlation filter based mechanism provides the capability to suppress noise, clutter and occlusion. Minimum Average Correlation Energy (MACE) filter yields sharp correlation peaks while considering the controlled correlation peak value. Difference of Gaussian (DOG) Wavelet has been added at the preprocessing stage in proposed filter design that facilitates target detection in orientation variant cluttered environment. Logarithmic transformation is combined with a DOG composite minimum average correlation energy filter (WMACE), capable of producing sharp correlation peaks despite any kind of geometric distortion of target object. The proposed filter has shown improved performance over some of the other variant correlation filters which are discussed in the result section.

Potential surface for the collinear collision of Ne and H/sub 2//sup +/. [eendoergicity, surface parametrization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, E.F.; Siu, A.K.Q.; Chapman, F.M. Jr.

1976-09-01

A potential energy surface for the Ne--H/sub 2//sup +/ reaction has been obtained in the LCAO--MO--SCF approximation. Analysis of the surface indicates that the reaction Ne+H/sub 2//sup +/..-->..NeH/sup +/+H should proceed with an endoergicity of 12 kcal/mole, in agreement with the experimental results of Chupka and Russell. Several procedures for parameterizing a diatomics-in-molecules (DIM) representation of the NeH/sub 2//sup +/ surface are considered. The results show that an accurate representation of the SCF surface can be obtained from the DIM model using a minimum of diatomic and triatomic data. (AIP)

A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denis-Alpizar, Otoniel, E-mail: otonieldenisalpizar@gmail.com; Departamento de Física, Universidad de Matanzas, Matanzas 40100; Kalugina, Yulia

We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H{sub 2}. Ab initio calculations of the HCN–H{sub 2} van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN–H{sub 2} with the nitrogen pointing towards H{sub 2} at an intermolecular separation of 7.20 a{sub 0}. The corresponding well depth is −195.20 cm{sup −1}. A secondary minimum of −183.59 cm{sup −1}more » was found for a T-shape configuration with the H of HCN pointing to the center of mass of H{sub 2}. We also determine the rovibrational energy levels of the HCN–para-H{sub 2} and HCN–ortho-H{sub 2} complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm{sup −1} and 60.26 cm{sup −1}, respectively. The calculated ro-vibrational transitions in the HCN–H{sub 2} complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.« less

Magnetic energy dissipation in force-free jets

NASA Technical Reports Server (NTRS)

Choudhuri, Arnab Rai; Konigl, Arieh

1986-01-01

It is shown that a magnetic pressure-dominated, supersonic jet which expands or contracts in response to variations in the confining external pressure can dissipate magnetic energy through field-line reconnection as it relaxes to a minimum-energy configuration. In order for a continuous dissipation to occur, the effective reconnection time must be a fraction of the expansion time. The dissipation rate for the axisymmetric minimum-energy field configuration is analytically derived. The results indicate that the field relaxation process could be a viable mechanism for powering the synchrotron emission in extragalactic jets if the reconnection time is substantially shorter than the nominal resistive tearing time in the jet.

Resolving the 180-degree ambiguity in vector magnetic field measurements: The 'minimum' energy solution

NASA Technical Reports Server (NTRS)

Metcalf, Thomas R.

1994-01-01

I present a robust algorithm that resolves the 180-deg ambiguity in measurements of the solar vector magnetic field. The technique simultaneously minimizes both the divergence of the magnetic field and the electric current density using a simulated annealing algorithm. This results in the field orientation with approximately minimum free energy. The technique is well-founded physically and is simple to implement.

Two-body potential model based on cosine series expansion for ionic materials

DOE PAGES

Oda, Takuji; Weber, William J.; Tanigawa, Hisashi

2015-09-23

There is a method to construct a two-body potential model for ionic materials with a Fourier series basis and we examine it. For this method, the coefficients of cosine basis functions are uniquely determined by solving simultaneous linear equations to minimize the sum of weighted mean square errors in energy, force and stress, where first-principles calculation results are used as the reference data. As a validation test of the method, potential models for magnesium oxide are constructed. The mean square errors appropriately converge with respect to the truncation of the cosine series. This result mathematically indicates that the constructed potentialmore » model is sufficiently close to the one that is achieved with the non-truncated Fourier series and demonstrates that this potential virtually provides minimum error from the reference data within the two-body representation. The constructed potential models work appropriately in both molecular statics and dynamics simulations, especially if a two-step correction to revise errors expected in the reference data is performed, and the models clearly outperform two existing Buckingham potential models that were tested. Moreover, the good agreement over a broad range of energies and forces with first-principles calculations should enable the prediction of materials behavior away from equilibrium conditions, such as a system under irradiation.« less

International Experience in Standards and Labeling Programs for Rice Cookers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Nan; Zheng, Nina

China has had an active program on energy efficiency standards for household appliances since the mid-1990s. Rice cooker is among the first to be subject to such mandatory regulation, since it is one of the most prevalent electric appliances in Chinese households. Since first introduced in 1989, the minimum energy efficiency standard for rice cookers has not been revised. Therefore, the potential for energy saving is considerable. Initial analysis from CNIS indicates that potential carbon savings is likely to reach 7.6 million tons of CO2 by the 10th year of the standard implementation. Since September 2007, CNIS has been workingmore » with various groups to develop the new standard for rice cookers. With The Energy Foundation's support, LBNL has assisted CNIS in the revision of the minimum energy efficiency standard for rice cookers that is expected to be effective in 2009. Specifically, work has been in the following areas: assistance in developing consumer survey on usage pattern of rice cookers, review of international standards, review of international test procedures, comparison of the international standards and test procedures, and assessment of technical options of reducing energy use. This report particularly summarizes the findings of reviewing international standards and technical options of reducing energy consumption. The report consists of an overview of rice cooker standards and labeling programs and testing procedures in Hong Kong, South Korea, Japan and Thailand, and Japan's case study in developing energy efficiency rice cooker technologies and rice cooker efficiency programs. The results from the analysis can be summarized as the follows: Hong Kong has a Voluntary Energy Efficiency Labeling scheme for electric rice cookers initiated in 2001, with revision implemented in 2007; South Korea has both MEPS and Mandatory Energy Efficiency Label targeting the same category of rice cookers as Hong Kong; Thailand's voluntary endorsement labeling program is similar to Hong Kong in program design but has 5 efficiency grades; Japan's program is distinct in its adoption of the 'Top Runner' approach, in which, the future efficiency standards is set based on the efficiency levels of the most efficient product in the current domestic market. Although the standards are voluntary, penalties can still be evoked if the average efficiency target is not met. Both Hong Kong and South Korea's tests involve pouring water into the inner pot equal to 80% of its rated volume; however, white rice is used as a load for its tests in Hong Kong whereas no rice is used for tests in South Korea. In Japan's case, water level specified by the manufactures is used and milled rice is used as a load only partially in the tests. Moreover, Japan does not conduct heat efficiency test but its energy consumption measurements tests are much more complex, with 4 different tests are conducted to determine the annual average energy consumption. Hong Kong and Thailand both set Minimum Allowable Heat Efficiency for different rated wattages. The energy efficiency requirements are identical except that the minimum heat efficiency in Thailand is 1 percentage point higher for all rated power categories. In South Korea, MEPS and label's energy efficiency grades are determined by the rice cooker's Rated Energy Efficiency for induction, non-induction, pressure, nonpressure rice cookers. Japan's target standard values are set for electromagnetic induction heating products and non-electromagnetic induction heating products by different size of rice cookers. Specific formulas are used by type and size depending on the mass of water evaporation of the rice cookers. Japan has been the leading country in technology development of various types of rice cookers, and developed concrete energy efficiency standards for rice cookers. However, as consumers in Japan emphasize the deliciousness of cooked rice over other factors, many types of models were developed to improve the taste of cooked rice. Nonetheless, the efficiency of electromagnetic induction heating (IH) rice cookers in warm mode has improved approximately 12 percent from 1993 to 2004 due to the 'low temperature warming method' developed by manufacturers. The Energy Conservation Center of Japan (IEEJ) releases energy saving products database on the web regularly, on which the energy saving performance of each product is listed and ranked. Energy saving in rice cookers mostly rest with insulation of the pot. Technology developed to improve the energy efficiency of the rice cookers includes providing vacuum layers on both side of the pot, using copper-plated materials, and double stainless layer lid that can be heated and steam can run in between the two layers to speed the heating process.« less

Elemental GCR Observations during the 2009-2010 Solar Minimum Period

NASA Technical Reports Server (NTRS)

Lave, K. A.; Israel, M. H.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.;

WindWaveFloat (WWF): Final Scientific Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alla Weinstein; Roddier, Dominique; Banister, Kevin

2012-03-30

Principle Power Inc. and National Renewable Energy Lab (NREL) have completed a contract to assess the technical and economic feasibility of integrating wave energy converters into the WindFloat, resulting in a new concept called the WindWaveFloat (WWF). The concentration of several devices on one platform could offer a potential for both economic and operational advantages. Wind and wave energy converters can share the electrical cable and power transfer equipment to transport the electricity to shore. Access to multiple generation devices could be simplified, resulting in cost saving at the operational level. Overall capital costs may also be reduced, provided thatmore » the design of the foundation can be adapted to multiple devices with minimum modifications. Finally, the WindWaveFloat confers the ability to increase energy production from individual floating support structures, potentially leading to a reduction in levelized energy costs, an increase in the overall capacity factor, and greater stability of the electrical power delivered to the grid. The research conducted under this grant investigated the integration of several wave energy device types into the WindFloat platform. Several of the resulting system designs demonstrated technical feasibility, but the size and design constraints of the wave energy converters (technical and economic) make the WindWaveFloat concept economically unfeasible at this time. Not enough additional generation could be produced to make the additional expense associated with wave energy conversion integration into the WindFloat worthwhile.« less

Neural-network-assisted genetic algorithm applied to silicon clusters

NASA Astrophysics Data System (ADS)

Marim, L. R.; Lemes, M. R.; dal Pino, A.

2003-03-01

Recently, a new optimization procedure that combines the power of artificial neural-networks with the versatility of the genetic algorithm (GA) was introduced. This method, called neural-network-assisted genetic algorithm (NAGA), uses a neural network to restrict the search space and it is expected to speed up the solution of global optimization problems if some previous information is available. In this paper, we have tested NAGA to determine the ground-state geometry of Sin (10⩽n⩽15) according to a tight-binding total-energy method. Our results indicate that NAGA was able to find the desired global minimum of the potential energy for all the test cases and it was at least ten times faster than pure genetic algorithm.

Improved Reweighting of Accelerated Molecular Dynamics Simulations for Free Energy Calculation.

PubMed

Miao, Yinglong; Sinko, William; Pierce, Levi; Bucher, Denis; Walker, Ross C; McCammon, J Andrew

2014-07-08

Accelerated molecular dynamics (aMD) simulations greatly improve the efficiency of conventional molecular dynamics (cMD) for sampling biomolecular conformations, but they require proper reweighting for free energy calculation. In this work, we systematically compare the accuracy of different reweighting algorithms including the exponential average, Maclaurin series, and cumulant expansion on three model systems: alanine dipeptide, chignolin, and Trp-cage. Exponential average reweighting can recover the original free energy profiles easily only when the distribution of the boost potential is narrow (e.g., the range ≤20 k B T) as found in dihedral-boost aMD simulation of alanine dipeptide. In dual-boost aMD simulations of the studied systems, exponential average generally leads to high energetic fluctuations, largely due to the fact that the Boltzmann reweighting factors are dominated by a very few high boost potential frames. In comparison, reweighting based on Maclaurin series expansion (equivalent to cumulant expansion on the first order) greatly suppresses the energetic noise but often gives incorrect energy minimum positions and significant errors at the energy barriers (∼2-3 k B T). Finally, reweighting using cumulant expansion to the second order is able to recover the most accurate free energy profiles within statistical errors of ∼ k B T, particularly when the distribution of the boost potential exhibits low anharmonicity (i.e., near-Gaussian distribution), and should be of wide applicability. A toolkit of Python scripts for aMD reweighting "PyReweighting" is distributed free of charge at http://mccammon.ucsd.edu/computing/amdReweighting/.

Improved Reweighting of Accelerated Molecular Dynamics Simulations for Free Energy Calculation

PubMed Central

2015-01-01

Accelerated molecular dynamics (aMD) simulations greatly improve the efficiency of conventional molecular dynamics (cMD) for sampling biomolecular conformations, but they require proper reweighting for free energy calculation. In this work, we systematically compare the accuracy of different reweighting algorithms including the exponential average, Maclaurin series, and cumulant expansion on three model systems: alanine dipeptide, chignolin, and Trp-cage. Exponential average reweighting can recover the original free energy profiles easily only when the distribution of the boost potential is narrow (e.g., the range ≤20kBT) as found in dihedral-boost aMD simulation of alanine dipeptide. In dual-boost aMD simulations of the studied systems, exponential average generally leads to high energetic fluctuations, largely due to the fact that the Boltzmann reweighting factors are dominated by a very few high boost potential frames. In comparison, reweighting based on Maclaurin series expansion (equivalent to cumulant expansion on the first order) greatly suppresses the energetic noise but often gives incorrect energy minimum positions and significant errors at the energy barriers (∼2–3kBT). Finally, reweighting using cumulant expansion to the second order is able to recover the most accurate free energy profiles within statistical errors of ∼kBT, particularly when the distribution of the boost potential exhibits low anharmonicity (i.e., near-Gaussian distribution), and should be of wide applicability. A toolkit of Python scripts for aMD reweighting “PyReweighting” is distributed free of charge at http://mccammon.ucsd.edu/computing/amdReweighting/. PMID:25061441

10 CFR 905.16 - What are the requirements for the minimum investment report alternative?

Code of Federal Regulations, 2013 CFR

2013-01-01

... report alternative? 905.16 Section 905.16 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT...; renewable energy; efficiency and alternative energy-related research and development; low-income energy... collected for and spent on DSM, renewable energy, efficiency or alternative energy-related research and...

10 CFR 905.16 - What are the requirements for the minimum investment report alternative?

Code of Federal Regulations, 2014 CFR

2014-01-01

... report alternative? 905.16 Section 905.16 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT...; renewable energy; efficiency and alternative energy-related research and development; low-income energy... collected for and spent on DSM, renewable energy, efficiency or alternative energy-related research and...

10 CFR 905.16 - What are the requirements for the minimum investment report alternative?

Code of Federal Regulations, 2011 CFR

2011-01-01

... report alternative? 905.16 Section 905.16 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT...; renewable energy; efficiency and alternative energy-related research and development; low-income energy... collected for and spent on DSM, renewable energy, efficiency or alternative energy-related research and...

10 CFR 905.16 - What are the requirements for the minimum investment report alternative?

Code of Federal Regulations, 2012 CFR

2012-01-01

... report alternative? 905.16 Section 905.16 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT...; renewable energy; efficiency and alternative energy-related research and development; low-income energy... collected for and spent on DSM, renewable energy, efficiency or alternative energy-related research and...

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model.

PubMed

Plotnikov, Nikolay V

2014-08-12

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force.

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model

PubMed Central

2015-01-01

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force. PMID:25136268

A systematic study of posterior cervical lymph node irradiation with electrons: Conventional versus customized planning.

PubMed

Jankowska, Petra J; Kong, Christine; Burke, Kevin; Harrington, Kevin J; Nutting, Christopher

2007-10-01

High dose irradiation of the posterior cervical lymph nodes usually employs applied electron fields to treat the target volume and maintain the spinal cord dose within tolerance. In the light of recent advances in elective lymph node localisation we investigated optimization of field shape and electron energy to treat this target volume. In this study, three sequential hypotheses were tested. Firstly, that customization of the electron fields based on the nodal PTV outlined gives better PTV coverage than conventional field delineation. Using the consensus guidelines, customization of the electron field shape was compared to conventional fields based on bony landmarks. Secondly, that selection of electron energy using DVHs for spinal cord and PTV improves the minimum dose to PTV. Electron dose-volume histograms (DVHs) for the PTV, spinal cord and para-vertebral muscles, were generated using the Monte Carlo electron algorithm. These DVHs were used to compare standard vs optimized electron energy calculations. Finally, that combination of field customization and electron energy optimization improves both the minimum and mean doses to PTV compared with current standard practice. Customized electron beam shaping based on the consensus guidelines led to fewer geographical misses than standard field shaping. Customized electron energy calculation led to higher minimum doses to the PTV. Overall, the customization of field shape and energy resulted in an improved mean dose to the PTV (92% vs 83% p=0.02) and a 27% improvement in the minimum dose delivered to the PTV (45% vs 18% p=0.0009). Optimization of electron field shape and beam energy based on current consensus guidelines led to significant improvement in PTV coverage and may reduce recurrence rates.

The Quantum Dynamics of Chemical Reactions.

DTIC Science & Technology

1983-03-31

of the potential formed by taking a cut perpendicular to the minimum energy path (in Delves coordinates) V (s) = VmeP(s) + Ev(S) (5) ve sn where s is...current density and profiles of the component of jo normal to various straight-line cuts along the streamline field, for the H + H2(0) - H 2 + H...In order to visualize the nature of this topology, we display in Fig. 31 cuts of the equipotentials of V by the XZ. (y. - 0, x) and Y.Z, (’. - n/2, -x

Spacetime dynamics of a Higgs vacuum instability during inflation

DOE PAGES

East, William E.; Kearney, John; Shakya, Bibhushan; ...

2017-01-31

A remarkable prediction of the Standard Model is that, in the absence of corrections lifting the energy density, the Higgs potential becomes negative at large field values. If the Higgs field samples this part of the potential during inflation, the negative energy density may locally destabilize the spacetime. Here, we use numerical simulations of the Einstein equations to study the evolution of inflation-induced Higgs fluctuations as they grow towards the true (negative-energy) minimum. Our simulations show that forming a single patch of true vacuum in our past light cone during inflation is incompatible with the existence of our Universe; themore » boundary of the true vacuum region grows outward in a causally disconnected manner from the crunching interior, which forms a black hole. We also find that these black hole horizons may be arbitrarily elongated—even forming black strings—in violation of the hoop conjecture. Furthermore, by extending the numerical solution of the Fokker-Planck equation to the exponentially suppressed tails of the field distribution at large field values, we derive a rigorous correlation between a future measurement of the tensor-to-scalar ratio and the scale at which the Higgs potential must receive stabilizing corrections in order for the Universe to have survived inflation until today.« less

Three Essays In and Tests of Theoretical Urban Economics

NASA Astrophysics Data System (ADS)

Zhao, Weihua

This dissertation consists of three essays on urban economics. The three essays are related to urban spatial structure change, energy consumption, greenhouse gas emissions, and housing redevelopment. Chapter 1 answers the question: Does the classic Standard Urban Model still describe the growth of cities? Chapter 2 derives the implications of telework on urban spatial structure, energy consumption, and greenhouse gas emissions. Chapter 3 investigates the long run effects of minimum lot size zoning on neighborhood redevelopment. Chapter 1 identifies a new implication of the classic Standard Urban Model, the "unitary elasticity property (UEP)", which is the sum of the elasticity of central density and the elasticity of land area with respect to population change is approximately equal to unity. When this implication of the SUM is tested, it fits US cities fairly well. Further analysis demonstrates that topographic barriers and age of housing stock are the key factors explaining deviation from the UEP. Chapter 2 develops a numerical urban simulation model with households that are able to telework to investigate the urban form, congestion, energy consumption and greenhouse gas emission implications of telework. Simulation results suggest that by reducing transportation costs, telework causes sprawl, with associated longer commutes and consumption of larger homes, both of which increase energy consumption. Overall effects depend on who captures the gains from telework (workers versus firms), urban land use regulation such as height limits or greenbelts, and the fraction of workers participating in telework. The net effects of telework on energy use and GHG emissions are generally negligible. Chapter 3 applies dynamic programming to investigate the long run effects of minimum lot size zoning on neighborhood redevelopment. With numerical simulation, comparative dynamic results show that minimum lot size zoning can delay initial land conversion and slow down demolition and housing redevelopment. Initially, minimum lot size zoning is not binding. However, as city grows, it becomes binding and can effectively distort housing supply. It can lower both floor area ratio and residential density, and reduce aggregate housing supply. Overall, minimum lot size zoning can stabilize the path of structure/land ratios, housing service levels, structure density, and housing prices. In addition, minimum lot size zoning provides more incentive for developer to maintain the building, slow structure deterioration, and raise the minimum level of housing services provided over the life cycle of development.

Development of Low-Carbon, Copper-Strengthened HSLA Steel Plate for Naval Ship Construction

DTIC Science & Technology

1990-06-01

steel plate microstructures, 2% nital etch . ...................................................... 13 2. Charpy V-notch impact energy transition for...met a minimum yield strength requirement of 80 ksi yield strength through 3/4 inch gage, had high Charpy V-notch impact energy at low tempera- tures...tempered HSLA line-pipe steels, which typically could not meet the minimum Charpy V-notch impact toughness requirement of 35 ft-lb at -1 200 F. In 1984

Dynamical correlation effects on photoisomerization: Ab initio multiple spawning dynamics with MS-CASPT2 for a model trans-protonated Schiff base

DOE PAGES

Liu, Lihong; Liu, Jian; Martinez, Todd J.

2015-12-17

Here, we investigate the photoisomerization of a model retinal protonated Schiff base (trans-PSB3) using ab initio multiple spawning (AIMS) based on multi-state second order perturbation theory (MSPT2). Discrepancies between the photodynamical mechanism computed with three-root state-averaged complete active space self-consistent field (SA-3-CASSCF, which does not include dynamic electron correlation effects) and MSPT2 show that dynamic correlation is critical in this photoisomerization reaction. Furthermore, we show that the photodynamics of trans-PSB3 is not well described by predictions based on minimum energy conical intersections (MECIs) or minimum energy conical intersection (CI) seam paths. Instead, most of the CIs involved in the photoisomerizationmore » are far from MECIs and minimum energy CI seam paths. Thus, both dynamical nuclear effects and dynamic electron correlation are critical to understanding the photochemical mechanism.« less

Synthesis of correlation filters: a generalized space-domain approach for improved filter characteristics

NASA Astrophysics Data System (ADS)

Sudharsanan, Subramania I.; Mahalanobis, Abhijit; Sundareshan, Malur K.

1990-12-01

Discrete frequency domain design of Minimum Average Correlation Energy filters for optical pattern recognition introduces an implementational limitation of circular correlation. An alternative methodology which uses space domain computations to overcome this problem is presented. The technique is generalized to construct an improved synthetic discriminant function which satisfies the conflicting requirements of reduced noise variance and sharp correlation peaks to facilitate ease of detection. A quantitative evaluation of the performance characteristics of the new filter is conducted and is shown to compare favorably with the well known Minimum Variance Synthetic Discriminant Function and the space domain Minimum Average Correlation Energy filter, which are special cases of the present design.

Theoretical/best practice energy use in metalcasting operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schifo, J. F.; Radia, J. T.

2004-05-01

This study determined the theoretical minimum energy requirements for melting processes for all ferrous and noferrous engenieering alloys. Also the report details the Best Practice energy consumption for the industry.

Energetic constraints on life in deep marine sediments

NASA Astrophysics Data System (ADS)

Amend, J.; LaRowe, D.

2013-12-01

Microorganisms are abundant in deep-sea sediments, but what percentage of cells is active, how fast do they grow, and what factors control their diversity and population size? Geochemical modelling of redox reaction energetics can help in answering these questions. Calculations of Gibbs energies reveal which reactions are thermodynamically possible, but they also highlight which geochemical variables (e.g., temperature, pressure, pH, composition) may control microbial activity and how the amount and type of biomass are affected by energy limitations. We will discuss recent results from sediment cores collected at the Peru Margin (active continental shelf with high primary productivity and significant organic matter accumulation), the South Pacific Gyre (ultra-slow sedimentation rate and low organic carbon content), and the Juan de Fuca Ridge flank (high rate of sedimentation influenced by hydrothermal circulation). However, this approach to evaluating bioenergetic potential and predicting microbial activity can be applied to any environment where the geochemistry is well characterized, even if microbiology data have not been collected. When Gibbs energies are calculated on a basis of per mole of electrons transferred (as is commonly done), aerobic oxidation of hydrogen and organic matter in South Pacific Gyre sediments is the most exergonic. Based on this, one might posit that the fastest catabolic rates and the largest biomass would be found there. However, cell counts at Juan de Fuca and the Peru Margin are several orders of magnitude higher. When recast as energy densities (in J per cm3 of sediment), we observe far more energy available in sediments at Juan de Fuca and the Peru Margin than at those in the South Pacific Gyre. We also note that the identity of the most exergonic reaction changes with depth, suggesting corresponding changes in the microbial community structure. The thermodynamic approach used here for energy supply can also be used for energy demand, including the often-considered minimum or threshold energy, also referred to as the biological energy quantum. Based on this energetic minimum theory, many reactions cannot support microbial communities because their energy yield is apparently too low. However, we show that when evaluated as energy densities, some energetically ';impossible' catabolisms become ';possible' and vice versa.

Isomers and energy landscapes of micro-hydrated sulfite and chlorate clusters

NASA Astrophysics Data System (ADS)

Hey, John C.; Doyle, Emily J.; Chen, Yuting; Johnston, Roy L.

2018-03-01

We present putative global minima for the micro-hydrated sulfite SO32-(H2O)N and chlorate ClO32(H2O)N systems in the range 3≤N≤15 found using basin-hopping global structure optimization with an empirical potential. We present a structural analysis of the hydration of a large number of minimized structures for hydrated sulfite and chlorate clusters in the range 3≤N≤50. We show that sulfite is a significantly stronger net acceptor of hydrogen bonding within water clusters than chlorate, completely suppressing the appearance of hydroxyl groups pointing out from the cluster surface (dangling OH bonds), in low-energy clusters. We also present a qualitative analysis of a highly explored energy landscape in the region of the global minimum of the eight water hydrated sulfite and chlorate systems. This article is part of the theme issue `Modern theoretical chemistry'.

Size-guided multi-seed heuristic method for geometry optimization of clusters: Application to benzene clusters.

PubMed

Takeuchi, Hiroshi

2018-05-08

Since searching for the global minimum on the potential energy surface of a cluster is very difficult, many geometry optimization methods have been proposed, in which initial geometries are randomly generated and subsequently improved with different algorithms. In this study, a size-guided multi-seed heuristic method is developed and applied to benzene clusters. It produces initial configurations of the cluster with n molecules from the lowest-energy configurations of the cluster with n - 1 molecules (seeds). The initial geometries are further optimized with the geometrical perturbations previously used for molecular clusters. These steps are repeated until the size n satisfies a predefined one. The method locates putative global minima of benzene clusters with up to 65 molecules. The performance of the method is discussed using the computational cost, rates to locate the global minima, and energies of initial geometries. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Isomers and energy landscapes of micro-hydrated sulfite and chlorate clusters.

PubMed

Hey, John C; Doyle, Emily J; Chen, Yuting; Johnston, Roy L

2018-03-13

We present putative global minima for the micro-hydrated sulfite SO 3 2- (H 2 O) N and chlorate ClO 3 - (H 2 O) N systems in the range 3≤ N ≤15 found using basin-hopping global structure optimization with an empirical potential. We present a structural analysis of the hydration of a large number of minimized structures for hydrated sulfite and chlorate clusters in the range 3≤ N ≤50. We show that sulfite is a significantly stronger net acceptor of hydrogen bonding within water clusters than chlorate, completely suppressing the appearance of hydroxyl groups pointing out from the cluster surface (dangling OH bonds), in low-energy clusters. We also present a qualitative analysis of a highly explored energy landscape in the region of the global minimum of the eight water hydrated sulfite and chlorate systems.This article is part of the theme issue 'Modern theoretical chemistry'. © 2018 The Authors.

Variational prediction of the mechanical behavior of shape memory alloys based on thermal experiments

NASA Astrophysics Data System (ADS)

Junker, Philipp; Jaeger, Stefanie; Kastner, Oliver; Eggeler, Gunther; Hackl, Klaus

2015-07-01

In this work, we present simulations of shape memory alloys which serve as first examples demonstrating the predicting character of energy-based material models. We begin with a theoretical approach for the derivation of the caloric parts of the Helmholtz free energy. Afterwards, experimental results for DSC measurements are presented. Then, we recall a micromechanical model based on the principle of the minimum of the dissipation potential for the simulation of polycrystalline shape memory alloys. The previously determined caloric parts of the Helmholtz free energy close the set of model parameters without the need of parameter fitting. All quantities are derived directly from experiments. Finally, we compare finite element results for tension tests to experimental data and show that the model identified by thermal measurements can predict mechanically induced phase transformations and thus rationalize global material behavior without any further assumptions.

Thermal energy storage for the Stirling engine powered automobile

NASA Technical Reports Server (NTRS)

Morgan, D. T. (Editor)

1979-01-01

A thermal energy storage (TES) system developed for use with the Stirling engine as an automotive power system has gravimetric and volumetric storage densities which are competitive with electric battery storage systems, meets all operational requirements for a practical vehicle, and can be packaged in compact sized automobiles with minimum impact on passenger and freight volume. The TES/Stirling system is the only storage approach for direct use of combustion heat from fuel sources not suitable for direct transport and use on the vehicle. The particular concept described is also useful for a dual mode TES/liquid fuel system in which the TES (recharged from an external energy source) is used for short duration trips (approximately 10 miles or less) and liquid fuel carried on board the vehicle used for long duration trips. The dual mode approach offers the potential of 50 percent savings in the consumption of premium liquid fuels for automotive propulsion in the United States.

Vibronic coupling and selectivity of vibrational excitation in the negative ion resonances of ozone

NASA Astrophysics Data System (ADS)

Allan, Michael; Popovic̀, Duška B.

1997-04-01

A recent experimental paper reported two shape resonances in electron impact on ozone, A 1 and B 2, both causing vibrational excitation with a distinct pattern of selectivity. The present Letter attempts to rationalize this selectivity using approximate potential curves, calculated for the A 1 and B 2 resonances by adding the SCF energy of neutral ozone to electron attachment energies calculated from ab initio virtual orbital energies using the Koopmans' theorem and an empirical scaling relation. The slopes of the curves explain the efficient excitation of the symmetric stretch by both resonances and the lack of the bending excitation by the B 2 resonance. The A 1 and B 2 resonances are strongly coupled by the b 2 antisymmetric stretch vibration, causing a double minimum on the lower surface. Nonadiabatic effects caused by the strong vibronic coupling explain the observed excitation of the antisymmetric stretch vibration.

General bounds in Hybrid Natural Inflation

NASA Astrophysics Data System (ADS)

Germán, Gabriel; Herrera-Aguilar, Alfredo; Hidalgo, Juan Carlos; Sussman, Roberto A.; Tapia, José

2017-12-01

Recently we have studied in great detail a model of Hybrid Natural Inflation (HNI) by constructing two simple effective field theories. These two versions of the model allow inflationary energy scales as small as the electroweak scale in one of them or as large as the Grand Unification scale in the other, therefore covering the whole range of possible energy scales. In any case the inflationary sector of the model is of the form V(phi)=V0 (1+a cos(phi/f)) where 0<= a<1 and the end of inflation is triggered by an independent waterfall field. One interesting characteristic of this model is that the slow-roll parameter epsilon(phi) is a non-monotonic function of phi presenting a maximum close to the inflection point of the potential. Because the scalar spectrum Script Ps(k) of density fluctuations when written in terms of the potential is inversely proportional to epsilon(phi) we find that Script Ps(k) presents a minimum at phimin. The origin of the HNI potential can be traced to a symmetry breaking phenomenon occurring at some energy scale f which gives rise to a (massless) Goldstone boson. Non-perturbative physics at some temperature T

Green Energy in New Construction: Maximize Energy Savings and Minimize Cost

ERIC Educational Resources Information Center

Ventresca, Joseph

2010-01-01

People often use the term "green energy" to refer to alternative energy technologies. But green energy doesn't guarantee maximum energy savings at a minimum cost--a common misconception. For school business officials, green energy means getting the lowest energy bills for the lowest construction cost, which translates into maximizing green energy…

Energy balance in high-quality cutting of steel by fiber and CO2 lasers

NASA Astrophysics Data System (ADS)

Fomin, V. M.; Golyshev, A. A.; Orishich, A. M.; Shulyat'ev, V. B.

2017-03-01

The energy balance of laser cutting of low-carbon and stainless steel sheets with the minimum roughness of the cut surface is experimentally studied. Experimental data obtained in wide ranges of cutting parameters are generalized with the use of dimensionless parameters (Peclet number and absorbed laser energy). It is discovered for the first time that the minimum roughness is ensured at a certain value of energy per unit volume of the melt (approximately 26 J/mm3), regardless of the gas type (oxygen or nitrogen) and laser type (fiber laser with a wavelength of 1.07 μm or CO2 laser with a wavelength of 10.6 μm).

TV Energy Consumption Trends and Energy-Efficiency Improvement Options

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Won Young; Phadke, Amol; Shah, Nihar

2011-07-01

The SEAD initiative aims to transform the global market by increasing the penetration of highly efficient equipment and appliances. SEAD is a government initiative whose activities and projects engage the private sector to realize the large global energy savings potential from improved appliance and equipment efficiency. SEAD seeks to enable high-level global action by informing the Clean Energy Ministerial dialogue as one of the initiatives in the Global Energy Efficiency Challenge. In keeping with its goal of achieving global energy savings through efficiency, SEAD was approved as a task within the International Partnership for Energy Efficiency Cooperation (IPEEC) in Januarymore » 2010. SEAD partners work together in voluntary activities to: (1) ?raise the efficiency ceiling? by pulling super-efficient appliances and equipment into the market through cooperation on measures like incentives, procurement, awards, and research and development (R&D) investments; (2) ?raise the efficiency floor? by working together to bolster national or regional policies like minimum efficiency standards; and (3) ?strengthen the efficiency foundations? of programs by coordinating technical work to support these activities. Although not all SEAD partners may decide to participate in every SEAD activity, SEAD partners have agreed to engage actively in their particular areas of interest through commitment of financing, staff, consultant experts, and other resources. In addition, all SEAD partners are committed to share information, e.g., on implementation schedules for and the technical detail of minimum efficiency standards and other efficiency programs. Information collected and created through SEAD activities will be shared among all SEAD partners and, to the extent appropriate, with the global public.As of April 2011, the governments participating in SEAD are: Australia, Brazil, Canada, the European Commission, France, Germany, India, Japan, Korea, Mexico, Russia, South Africa, Sweden, the United Arab Emirates, the United Kingdom, and the United States. More information on SEAD is available from its website at http://www.superefficient.org/.« less

Low energy isomers of (H2O)25 from a hierarchical method based on Monte Carlo Temperature Basin Paving and Molecular Tailoring Approaches benchmarked by full MP2 calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahu, Nityananda; Gadre, Shridhar R.; Bandyopadhyay, Pradipta

We report new global minimum candidate structures for the (H2O)25 cluster that are lower in energy than the ones reported previously and correspond to hydrogen bonded networks with 42 hydrogen bonds and an interior, fully coordinated water molecule. These were obtained as a result of a hierarchical approach based on initial Monte Carlo Temperature Basin Paving (MCTBP) sampling of the cluster’s Potential Energy Surface (PES) with the Effective Fragment Potential (EFP), subsequent geometry optimization using the Molecular Tailoring fragmentation Approach (MTA) and final refinement at the second order Møller Plesset perturbation (MP2) level of theory. The MTA geometry optimizations usedmore » between 14 and 18 main fragments with maximum sizes between 11 and 14 water molecules and average size of 10 water molecules, whose energies and gradients were computed at the MP2 level. The MTA-MP2 optimized geometries were found to be quite close (within < 0.5 kcal/mol) to the ones obtained from the MP2 optimization of the whole cluster. The grafting of the MTA-MP2 energies yields electronic energies that are within < 5×10-4 a.u. from the MP2 results for the whole cluster while preserving their energy order. The MTA-MP2 method was also found to reproduce the MP2 harmonic vibrational frequencies in both the HOH bending and the OH stretching regions.« less

Efficient Online Optimized Quantum Control for Adiabatic Quantum Computation

NASA Astrophysics Data System (ADS)

Quiroz, Gregory

Adiabatic quantum computation (AQC) relies on controlled adiabatic evolution to implement a quantum algorithm. While control evolution can take many forms, properly designed time-optimal control has been shown to be particularly advantageous for AQC. Grover's search algorithm is one such example where analytically-derived time-optimal control leads to improved scaling of the minimum energy gap between the ground state and first excited state and thus, the well-known quadratic quantum speedup. Analytical extensions beyond Grover's search algorithm present a daunting task that requires potentially intractable calculations of energy gaps and a significant degree of model certainty. Here, an in situ quantum control protocol is developed for AQC. The approach is shown to yield controls that approach the analytically-derived time-optimal controls for Grover's search algorithm. In addition, the protocol's convergence rate as a function of iteration number is shown to be essentially independent of system size. Thus, the approach is potentially scalable to many-qubit systems.

Mechanics of tunable helices and geometric frustration in biomimetic seashells

NASA Astrophysics Data System (ADS)

Guo, Qiaohang; Chen, Zi; Li, Wei; Dai, Pinqiang; Ren, Kun; Lin, Junjie; Taber, Larry A.; Chen, Wenzhe

2014-03-01

Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, add to the variety of this family of aesthetic beauty. Here we develop a comprehensive theoretical framework for tunable helical morphologies, and report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves equilibrium. In this work, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessarily be locally optimized. This novel approach can be applied to develop materials and devices of tunable geometries with a range of applications in nano/biotechnology.

Power Controller

NASA Technical Reports Server (NTRS)

1982-01-01

The device called the Power Factor Controller (PFC) offers exceptional energy conservation potential by virtue of its ability to sense shifts in the relationship between voltage and current flow, and to match them with the motor's need. Originating from the solar heating/cooling program, the PFC senses a light load, it cuts the voltage level to the minimum needed which in turn reduces current flow and heat loss. Laboratory tests showed that the PFC could reduce power used by six to eight percent under normal motor loads, and as much as 65 percent when the motor was idling. Over 150 companies have been granted NASA licenses for commercial use of this technology. One system that utilizes this technology is the Vectrol Energy System, (VES) produced by Vectrol, Inc. a subsidiary of Westinghouse. The VES is being used at Woodward & Lothrop, on their escalators. Energy use is regulated according to how many people are on the escalator at any time. It is estimated that the energy savings are between 30 to 40 percent.

GENESIS 1.1: A hybrid-parallel molecular dynamics simulator with enhanced sampling algorithms on multiple computational platforms.

PubMed

Kobayashi, Chigusa; Jung, Jaewoon; Matsunaga, Yasuhiro; Mori, Takaharu; Ando, Tadashi; Tamura, Koichi; Kamiya, Motoshi; Sugita, Yuji

2017-09-30

GENeralized-Ensemble SImulation System (GENESIS) is a software package for molecular dynamics (MD) simulation of biological systems. It is designed to extend limitations in system size and accessible time scale by adopting highly parallelized schemes and enhanced conformational sampling algorithms. In this new version, GENESIS 1.1, new functions and advanced algorithms have been added. The all-atom and coarse-grained potential energy functions used in AMBER and GROMACS packages now become available in addition to CHARMM energy functions. The performance of MD simulations has been greatly improved by further optimization, multiple time-step integration, and hybrid (CPU + GPU) computing. The string method and replica-exchange umbrella sampling with flexible collective variable choice are used for finding the minimum free-energy pathway and obtaining free-energy profiles for conformational changes of a macromolecule. These new features increase the usefulness and power of GENESIS for modeling and simulation in biological research. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Free energy surfaces for the interaction of D-glucose with planar aromatic groups in aqueous solution

NASA Astrophysics Data System (ADS)

Wohlert, Jakob; Schnupf, Udo; Brady, John W.

2010-10-01

Multidimensional potentials of mean force for the interactions in aqueous solution of both anomers of D-glucopyranose with two planar aromatic molecules, indole and para-methyl-phenol, have been calculated using molecular dynamics simulations with umbrella sampling and were subsequently used to estimate binding free energies. Indole and para-methyl-phenol serve as models for the side chains of the amino acids tryptophan and tyrosine, respectively. In all cases, a weak affinity between the glucose molecules and the flat aromatic surfaces was found. The global minimum for these interactions was found to be for the case when the pseudoplanar face of β-D-glucopyranose is stacked against the planar surfaces of the aromatic residues. The calculated binding free energies are in good agreement with both experiment and previous simulations. The multidimensional free energy maps suggest a mechanism that could lend kinetic stability to the complexes formed by sugars bound to sugar-binding proteins.

Two-component, ab initio potential energy surface for CO2—H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both

NASA Astrophysics Data System (ADS)

Wang, Qingfeng Kee; Bowman, Joel M.

2017-10-01

We report an ab initio, full-dimensional, potential energy surface (PES) for CO2—H2O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D0, of 787 cm-1 is obtained using that ZPE, De, and the rigorous ZPEs of the monomers. Using a benchmark De, D0 is 758 cm-1. Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO2 hydrate clathrate CO2(H2O)20(512 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO2.

Two-component, ab initio potential energy surface for CO2-H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both.

PubMed

Wang, Qingfeng Kee; Bowman, Joel M

2017-10-28

We report an ab initio, full-dimensional, potential energy surface (PES) for CO 2 -H 2 O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D 0 , of 787 cm -1 is obtained using that ZPE, D e , and the rigorous ZPEs of the monomers. Using a benchmark D e , D 0 is 758 cm -1 . Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO 2 hydrate clathrate CO 2 (H 2 O) 20 (5 12 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO 2 .

The energy requirements of an aircraft triggered discharge

NASA Astrophysics Data System (ADS)

Bicknell, J. A.; Shelton, R. W.

The corona produced at aircraft surfaces requires an energy input before the corona can develop into a high current discharge and, thus, a possible lightning stroke. This energy must be drawn from the space charge field of the thundercloud and, since this is of low density, the unique propagation characteristics of positive corona streamers may be important. Estimates of the energy made available by the propagation are compared with laboratory measurements of the minimum energy input required to trigger a breakdown. The comparison indicates a minimum streamer range for breakdown of several tens of meters. Also estimated is the energy released as a consequence of streamer-hydrometer interactions; this is shown to be significant so that breakdown could depend upon the precipitation rate within the cloud. Inhibiting streamer production may therefore provide an aircraft with a degree of corona protection.

Stepwise Catalytic Mechanism via Short-Lived Intermediate Inferred from Combined QM/MM MERP and PES Calculations on Retaining Glycosyltransferase ppGalNAcT2

PubMed Central

Trnka, Tomáš; Kozmon, Stanislav; Tvaroška, Igor; Koča, Jaroslav

2015-01-01

The glycosylation of cell surface proteins plays a crucial role in a multitude of biological processes, such as cell adhesion and recognition. To understand the process of protein glycosylation, the reaction mechanisms of the participating enzymes need to be known. However, the reaction mechanism of retaining glycosyltransferases has not yet been sufficiently explained. Here we investigated the catalytic mechanism of human isoform 2 of the retaining glycosyltransferase polypeptide UDP-GalNAc transferase by coupling two different QM/MM-based approaches, namely a potential energy surface scan in two distance difference dimensions and a minimum energy reaction path optimisation using the Nudged Elastic Band method. Potential energy scan studies often suffer from inadequate sampling of reactive processes due to a predefined scan coordinate system. At the same time, path optimisation methods enable the sampling of a virtually unlimited number of dimensions, but their results cannot be unambiguously interpreted without knowledge of the potential energy surface. By combining these methods, we have been able to eliminate the most significant sources of potential errors inherent to each of these approaches. The structural model is based on the crystal structure of human isoform 2. In the QM/MM method, the QM region consists of 275 atoms, the remaining 5776 atoms were in the MM region. We found that ppGalNAcT2 catalyzes a same-face nucleophilic substitution with internal return (SNi). The optimized transition state for the reaction is 13.8 kcal/mol higher in energy than the reactant while the energy of the product complex is 6.7 kcal/mol lower. During the process of nucleophilic attack, a proton is synchronously transferred to the leaving phosphate. The presence of a short-lived metastable oxocarbenium intermediate is likely, as indicated by the reaction energy profiles obtained using high-level density functionals. PMID:25849117

Stepwise catalytic mechanism via short-lived intermediate inferred from combined QM/MM MERP and PES calculations on retaining glycosyltransferase ppGalNAcT2.

PubMed

Trnka, Tomáš; Kozmon, Stanislav; Tvaroška, Igor; Koča, Jaroslav

2015-04-01

The glycosylation of cell surface proteins plays a crucial role in a multitude of biological processes, such as cell adhesion and recognition. To understand the process of protein glycosylation, the reaction mechanisms of the participating enzymes need to be known. However, the reaction mechanism of retaining glycosyltransferases has not yet been sufficiently explained. Here we investigated the catalytic mechanism of human isoform 2 of the retaining glycosyltransferase polypeptide UDP-GalNAc transferase by coupling two different QM/MM-based approaches, namely a potential energy surface scan in two distance difference dimensions and a minimum energy reaction path optimisation using the Nudged Elastic Band method. Potential energy scan studies often suffer from inadequate sampling of reactive processes due to a predefined scan coordinate system. At the same time, path optimisation methods enable the sampling of a virtually unlimited number of dimensions, but their results cannot be unambiguously interpreted without knowledge of the potential energy surface. By combining these methods, we have been able to eliminate the most significant sources of potential errors inherent to each of these approaches. The structural model is based on the crystal structure of human isoform 2. In the QM/MM method, the QM region consists of 275 atoms, the remaining 5776 atoms were in the MM region. We found that ppGalNAcT2 catalyzes a same-face nucleophilic substitution with internal return (SNi). The optimized transition state for the reaction is 13.8 kcal/mol higher in energy than the reactant while the energy of the product complex is 6.7 kcal/mol lower. During the process of nucleophilic attack, a proton is synchronously transferred to the leaving phosphate. The presence of a short-lived metastable oxocarbenium intermediate is likely, as indicated by the reaction energy profiles obtained using high-level density functionals.

Experimental and Modeling Study on Detachment of Silver Nanoparticles in Saturated Granular Media

NASA Astrophysics Data System (ADS)

Kim, I.; Jeon, C. H.; Lawler, D. F.

2017-12-01

The detachment of citrate-capped silver nanoparticles (AgNPs) previously captured in a column packed with 350-μm glass beads was investigated either by increasing the hydrodynamic force (filtration velocity) or by reducing electrosteric attraction. Overall, the physical enforcement showed negligible (0.4 0.7%) release of attached AgNPs while the chemically-driven force resulted in the noticeable release up to 25.5% of attached AgNPs. Among the chemical parameters tested in this study, Na ionic strength reduction clearly demonstrated the reversible deposition in the secondary energy minimum of classical DLVO theory, yielding the most significant release of the attached AgNPs. The immediate and transient AgNP release after the ionic strength reduction further corroborated the weak deposition. However, an insignificant release was observed with Ca ionic strength reduction due to the strong Ca-citrate complexation and the subsequent deposition in the primary energy minimum; calculations indicated that the depth of the secondary energy minimum was only 1/10 that of the Na ion case. The natural organic matter (NOM) coating on both AgNPs and granular media resulted in approximately 6.1% greater AgNP release compared to the case without NOM coating, indicating additional weak deposition due to the reduced steric attraction between AgNPs and granular media. A modified filtration model in agreement with the experimental data provided the estimated detachment coefficient as a transient AgNP releasing capacity independent of the amount of attached AgNPs. The marginal difference between the detachment coefficients from Na ionic strength reduction and NOM coating indicates the release potential by NOM coating was possibly underestimated in the experimental study due to a lesser amount of the initially attached AgNPs. The findings provide insights into chemical factors on possible reentrainment behavior of the engineered nanoparticles in soil and groundwater contamination.

Excited state conformational dynamics in carotenoids: dark intermediates and excitation energy transfer.

PubMed

Beck, Warren F; Bishop, Michael M; Roscioli, Jerome D; Ghosh, Soumen; Frank, Harry A

2015-04-15

A consideration of the excited state potential energy surfaces of carotenoids develops a new hypothesis for the nature of the conformational motions that follow optical preparation of the S2 (1(1)Bu(+)) state. After an initial displacement from the Franck-Condon geometry along bond length alternation coordinates, it is suggested that carotenoids pass over a transition-state barrier leading to twisted conformations. This hypothesis leads to assignments for several dark intermediate states encountered in femtosecond spectroscopic studies. The Sx state is assigned to the structure reached upon the onset of torsional motions near the transition state barrier that divides planar and twisted structures on the S2 state potential energy surface. The X state, detected recently in two-dimensional electronic spectra, corresponds to a twisted structure well past the barrier and approaching the S2 state torsional minimum. Lastly, the S(∗) state is assigned to a low lying S1 state structure with intramolecular charge transfer character (ICT) and a pyramidal conformation. It follows that the bent and twisted structures of carotenoids that are found in photosynthetic light-harvesting proteins yield excited-state structures that favor the development of an ICT character and optimized energy transfer yields to (bacterio)chlorophyll acceptors. Copyright © 2015 Elsevier Inc. All rights reserved.

Ab initio reaction pathways for photodissociation and isomerization of nitromethane on four singlet potential energy surfaces with three roaming paths

NASA Astrophysics Data System (ADS)

Isegawa, Miho; Liu, Fengyi; Maeda, Satoshi; Morokuma, Keiji

2014-06-01

Photodissociation pathways of nitromethane following π → π* electronic excitation are reported. The potential energy surfaces for four lowest singlet states are explored, and structures of many intermediates, dissociation limits, transition states, and minimum energy conical intersections were determined using the automated searching algorism called the global reaction route mapping strategy. Geometries are finally optimized at CASSCF(14e,11o) level and energies are computed at CAS(14o,11e)PT2 level. The calculated preferable pathways and important products qualitatively explain experimental observations. The major photodissociation product CH3 and NO2 (2B2) is formed by direct dissociation from the S1 state. Important pathways involving S1 and S0 states for production of various dissociation products CH3NO + O (1D), CH3O(X2E) + NO (X2Π), CH2NO + OH, and CH2O + HNO, as well as various isomerization pathways have been identified. Three roaming processes also have been identified: the O atom roaming in O dissociation from CH3NO2, the OH radical roaming in OH dissociation from CH2N(O)(OH), and the NO roaming in NO dissociation from CH3ONO.

Ab initio reaction pathways for photodissociation and isomerization of nitromethane on four singlet potential energy surfaces with three roaming paths.

PubMed

Isegawa, Miho; Liu, Fengyi; Maeda, Satoshi; Morokuma, Keiji

2014-06-28

Photodissociation pathways of nitromethane following π → π(*) electronic excitation are reported. The potential energy surfaces for four lowest singlet states are explored, and structures of many intermediates, dissociation limits, transition states, and minimum energy conical intersections were determined using the automated searching algorism called the global reaction route mapping strategy. Geometries are finally optimized at CASSCF(14e,11o) level and energies are computed at CAS(14o,11e)PT2 level. The calculated preferable pathways and important products qualitatively explain experimental observations. The major photodissociation product CH3 and NO2 ((2)B2) is formed by direct dissociation from the S1 state. Important pathways involving S1 and S0 states for production of various dissociation products CH3NO + O ((1)D), CH3O(X(2)E) + NO (X(2)Π), CH2NO + OH, and CH2O + HNO, as well as various isomerization pathways have been identified. Three roaming processes also have been identified: the O atom roaming in O dissociation from CH3NO2, the OH radical roaming in OH dissociation from CH2N(O)(OH), and the NO roaming in NO dissociation from CH3ONO.

Revised estimates of the ocean energy cycle and the key role of the western boundary in the APE to KE conversion due to high latitude cooling

NASA Astrophysics Data System (ADS)

Tailleux, Remi

2014-05-01

The ocean energy cycle is a key aspect of the ocean circulation, and has been traditionally framed in terms of Lorenz (1955) theory of available potential energy. However, the latest available observational estimate of the ocean energy cycle is due to Oort and Peixoto (1994) and is now very dated. Moreover, the latter estimate relies on the so-called Lorenz quasi-geostrophic approximation, which is known to be very inaccurate. Oort and Peixoto also neglected the internal energy contribution to the total available potential energy, which is now understood to be far from negligible, and to account for up to 40 percent of the total APE. The purpose of this work is to revisit observational estimates of the ocean energy cycle by taking advantage of a newly developed APE framework, as well as of the many new available observational products for temperature, salinity and surface buoyancy fluxes. In contrast to previous frameworks, our APE framework (Tailleux, 2013) relies on a physically well defined local APE definition, which is valid for a binary Boussinesq or fully compressible fluid with an arbitrary nonlinear equation of state. As part of our approach, we also developed a new fast and accurate way to construct Lorenz reference state of minimum potential energy, based on using the joint probability distribution function for temperature and salinity. Results will be presented for a variety of observational products, as well as for the ECCO2 ocean state estimate. The role of the deep western boundary as the place where the APE created by high latitude is converted into kinetic energy (KE) as part of driving the Atlantic meridional overturning circulation will be emphasized. References: Tailleux, R., 2013: Available potential energy density for a multicomponent Boussinesq fluid with arbitrary nonlinear equation of state.J. Fluid Mech., 735,499-518. Sijp, W., J.M.Gregory, R. Tailleux, P. Spence, 2012: The key role of the western boundary in linking the AMOC strength to the North South pressure gradient. J. Phys. Oceanogr., 42, 628-643.

Reduced Zeta potential through use of cationic adhesion promoter for improved resist process performance and minimizing material consumption

NASA Astrophysics Data System (ADS)

Hodgson, Lorna; Thompson, Andrew

2012-03-01

This paper presents the results of a non-HMDS (non-silane) adhesion promoter that was used to reduce the zeta potential for very thin (proprietary) polymer on silicon. By reducing the zeta potential, as measured by the minimum sample required to fully coat a wafer, the amount of polymer required to coat silicon substrates was significantly reduced in the manufacture of X-ray windows used for high transmission of low-energy X-rays. Moreover, this approach used aqueous based adhesion promoter described as a cationic surface active agent that has been shown to improve adhesion of photoresists (positive, negative, epoxy [SU8], e-beam and dry film). As well as reducing the amount of polymer required to coat substrates, this aqueous adhesion promoter is nonhazardous, and contains non-volatile solvents.

On the dynamics of superstring compactification

NASA Astrophysics Data System (ADS)

Pollock, M. D.

2018-05-01

Compactification of the ten-dimensional heterotic superstring theory to four dimensions gives rise to two moduli potentials VA, VB, the positive semi-definiteness of which places constraints on the Euler characteristic \\bar{χ} of the internal space \\bar{g}_{μν}(y^{ξ}) and the adiabatic index γ of the effective matter source of energy-density ρ and pressure p = (γ -1)ρ that generates the physical four-space g_{ij}(xk), namely \\bar{χ} < 0, 4/3 ≤ γ ≤ 2, or \\bar{χ} > 0, 1 ≤ γ ≤ 4/3. Here, we show how fermion-bilinear condensation in the internal space, first put forward by Helayël-Neto and Smith, determines the field \\tilde{β} ≡ A_r B_r3, thus reducing the moduli space to a single canonical field \\tilde{σ}=2σB with a potential ˜ , which is positive semi-definite under the same conditions that ensure positive semi-definiteness of VA, VB, and has a minimum at a value of \\tilde{β} that is approximately constant far from the Planck era at t ≫ t_P. The fields σA, σB, which are canonically normalized in the zero-slope limit, are modified by contributions originating from the higher-derivative gravitational terms α^' \\hatR_E2 and α^' 3} \\hatR4, but the associated kinetic energy remains positive for times t ≳ t_P/2, guaranteeing classical stability of the solution, since the generalized indeterminacy principle implies a minimum physically measurable time t0 ≈ 50 t_P for the superstring theory.

Ammonia-water cation and ammonia dimer cation.

PubMed

Kim, Hahn; Lee, Han Myoung

2009-06-25

We have investigated the structure, interaction energy, electronic properties, and IR spectra of the ammonia-water cation (NH(3)H(2)O)(+) using density functional theory (DFT) and high-level ab initio theory. The ammonia-water cation has three minimum-energy structures of (a) H(2)NH(+)...OH(2), (b) H(3)N(+)...OH(2), and (c) H(3)NH(+)...OH. The lowest-energy structure is (a), followed by (c) and (b). The ammonia dimer cation has two minimum-energy structures [the lowest H(3)NH(+)...NH(2) structure and the second lowest (H(3)N...NH(3))(+) structure]. The minimum transition barrier for the interconversion between (a), (b), and (c) is approximately 6 kcal/mol. Most DFT calculations with various functionals, except a few cases, overstabilize the N...O and N...N binding, predicting different structures from Moller-Plesset second-order perturbation (MP2) theory and the most reliable complete basis set (CBS) limit of coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)]. Thus, the validity test of the DFT functionals for these ionized molecular systems would be of importance.

Polymer-induced phase separation and crystallization in immunoglobulin G solutions.

PubMed

Li, Jianguo; Rajagopalan, Raj; Jiang, Jianwen

2008-05-28

We study the effects of the size of polymer additives and ionic strength on the phase behavior of a nonglobular protein-immunoglobulin G (IgG)-by using a simple four-site model to mimic the shape of IgG. The interaction potential between the protein molecules consists of a Derjaguin-Landau-Verwey-Overbeek-type colloidal potential and an Asakura-Oosawa depletion potential arising from the addition of polymer. Liquid-liquid equilibria and fluid-solid equilibria are calculated by using the Gibbs ensemble Monte Carlo technique and the Gibbs-Duhem integration (GDI) method, respectively. Absolute Helmholtz energy is also calculated to get an initial coexisting point as required by GDI. The results reveal a nonmonotonic dependence of the critical polymer concentration rho(PEG) (*) (i.e., the minimum polymer concentration needed to induce liquid-liquid phase separation) on the polymer-to-protein size ratio q (equivalently, the range of the polymer-induced depletion interaction potential). We have developed a simple equation for estimating the minimum amount of polymer needed to induce the liquid-liquid phase separation and show that rho(PEG) (*) approximately [q(1+q)(3)]. The results also show that the liquid-liquid phase separation is metastable for low-molecular weight polymers (q=0.2) but stable at large molecular weights (q=1.0), thereby indicating that small sizes of polymer are required for protein crystallization. The simulation results provide practical guidelines for the selection of polymer size and ionic strength for protein phase separation and crystallization.

10 CFR 429.44 - Commercial water heating equipment.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of minimum thermal efficiency or other measure of energy consumption of a basic model for which... 10 Energy 3 2013-01-01 2013-01-01 false Commercial water heating equipment. 429.44 Section 429.44 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION CERTIFICATION, COMPLIANCE, AND ENFORCEMENT FOR CONSUMER...

Minimum free-energy paths for the self-organization of polymer brushes.

PubMed

Gleria, Ignacio; Mocskos, Esteban; Tagliazucchi, Mario

2017-03-22

A methodology to calculate minimum free-energy paths based on the combination of a molecular theory and the improved string method is introduced and applied to study the self-organization of polymer brushes under poor solvent conditions. Polymer brushes in a poor solvent cannot undergo macroscopic phase separation due to the physical constraint imposed by the grafting points; therefore, they microphase separate forming aggregates. Under some conditions, the theory predicts that the homogeneous brush and the aggregates can exist as two different minima of the free energy. The theoretical methodology introduced in this work allows us to predict the minimum free-energy path connecting these two minima as well as the morphology of the system along the path. It is shown that the transition between the homogeneous brush and the aggregates may involve a free-energy barrier or be barrierless depending on the relative stability of the two morphologies and the chain length and grafting density of the polymer. In the case where a free-energy barrier exists, one of the morphologies is a metastable structure and, therefore, the properties of the brush as the quality of the solvent is cycled are expected to display hysteresis. The theory is also applied to study the adhesion/deadhesion transition between two opposing surfaces modified by identical polymer brushes and it is shown that this process may also require surpassing a free-energy barrier.

A thermodynamic approach to link self-organization, preferential flow and rainfall-runoff behaviour

NASA Astrophysics Data System (ADS)

Zehe, E.; Ehret, U.; Blume, T.; Kleidon, A.; Scherer, U.; Westhoff, M.

2013-11-01

This study investigates whether a thermodynamically optimal hillslope structure can, if existent, serve as a first guess for uncalibrated predictions of rainfall-runoff. To this end we propose a thermodynamic framework to link rainfall-runoff processes and dynamics of potential energy, kinetic energy and capillary binding energy in catchments and hillslopes. The starting point is that hydraulic equilibrium in soil corresponds to local thermodynamic equilibrium (LTE), characterized by a local maximum entropy/minimum of free energy of soil water. Deviations from LTE occur either due to evaporative losses, which increase absolute values of negative capillary binding energy of soil water and reduce its potential energy, or due to infiltration of rainfall, which increases potential energy of soil water and reduces the strength of capillary binding energy. The amplitude and relaxation time of these deviations depend on climate, vegetation, soil hydraulic functions, topography and density of macropores. Based on this framework we analysed the free energy balance of hillslopes within numerical experiments that perturbed model structures with respect to the surface density of macropores. These model structures have been previously shown to allow successful long-term simulations of the water balances of the Weiherbach and the Malalcahuello catchments, which are located in distinctly different pedological and climatic settings. Our findings offer a new perspective on different functions of preferential flow paths depending on the pedological setting. Free energy dynamics of soil water in the cohesive soils of the Weiherbach is dominated by dynamics of capillary binding energy. Macropores act as dissipative wetting structures by enlarging water flows against steep gradients in soil water potential after long dry spells. This implies accelerated depletion of these gradients and faster relaxation back towards LTE. We found two local optima in macropore density that maximize reduction rates of free energy of soil water during rainfall-driven conditions. These two optima exist because reduction rates of free energy are, in this case, a second-order polynomial of the wetting rate, which implicitly depends on macroporosity. An uncalibrated long-term simulation of the water balance of the Weiherbach catchment based on the first optimum macroporosity performed almost as well as the best fit when macroporosity was calibrated to match rainfall-runoff. In the Malalcahuello catchment we did not find an apparent optimum density of macropores, because free energy dynamics of soil water during rainfall-driven conditions is dominated by increases of potential energy. Macropores act as dissipative drainage structures by enhancing export of potential energy. No optimum macropore density exists in this case because potential energy change rates scale linearly with the wetting rate. We found, however, a distinguished macroporosity that assures steady-state conditions of the potential energy balance of the soil, in the sense that average storage of potential energy is compensated by average potential energy export. This distinguished macroporosity was close to the value that yielded the best fit of rainfall-runoff behaviour during a calibration exercise and allowed a robust estimate of the annual runoff coefficient. Our findings are promising for predictions in ungauged catchments (PUB) as the optimal/distinguished model structures can serve as a first guess for uncalibrated predictions of rainfall-runoff. They also offer an alternative for classifying catchments according to their similarity of the free energy balance components.

Ground state of high-density matter

NASA Technical Reports Server (NTRS)

Copeland, ED; Kolb, Edward W.; Lee, Kimyeong

1988-01-01

It is shown that if an upper bound to the false vacuum energy of the electroweak Higgs potential is satisfied, the true ground state of high-density matter is not nuclear matter, or even strange-quark matter, but rather a non-topological soliton where the electroweak symmetry is exact and the fermions are massless. This possibility is examined in the standard SU(3) sub C tensor product SU(2) sub L tensor product U(1) sub Y model. The bound to the false vacuum energy is satisfied only for a narrow range of the Higgs boson masses in the minimal electroweak model (within about 10 eV of its minimum allowed value of 6.6 GeV) and a somewhat wider range for electroweak models with a non-minimal Higgs sector.

Ab initio/DFT/GIAO-CCSD(T) calculational study of the t-butyl cation: comparison of experimental data with structures, energetics, IR vibrational frequencies, and 13C NMR chemical shifts indicating preferred C(s) conformation.

PubMed

Rasul, Golam; Chen, Jonathan L; Prakash, G K Surya; Olah, George A

2009-06-18

The C(s) conformation of the tert-butyl cation 3 was established to be the preferred global energy minimum using a combination of ab initio, DFT, and CCSD(T) methodology with correlation-consistent basis sets. The potential energy surface of methyl rotation involving the C(3v), C(s), and C(3h) forms, however, in accord with previous studies, is quite flat. The computed IR absorptions of 3 indicate that it has the greatest degree of electron donation from C-H bonds into the C(+)-C bonds. The experimental (13)C NMR chemical shifts also agree very well with the experimental data.

Mechanical behavior of cells in microinjection: a minimum potential energy study.

PubMed

Liu, Fei; Wu, Dan; Chen, Ken

2013-08-01

Microinjection is a widely used technique to deliver foreign materials into biological cells. We propose a mathematical model to study the mechanical behavior of a cell in microinjection. Firstly, a cell is modeled by a hyperelastic membrane and interior cytoplasm. Then, based on the fact that the equilibrium configuration of a cell would minimize the potential energy, the energy function during microinjection is analyzed. With Lagrange multiplier and Rayleigh-Ritz technique, we successfully minimize the potential energy and obtain the equilibrium configuration. Upon this model, the injection force, the injection distance, the radius of the microinjector and the membrane stress are studied. The analysis demonstrates that the microinjector radius has a significant influence on the cell mechanical behavior: (1) the larger radius generates larger injection force and larger interior pressure at the same injection distance; (2) the radius determines the place where the membrane is most likely to rupture by governing the membrane stress distribution. For a fine microinjector with radius less than 20% of the cell radius, the most likely rupture point located at the edge of the contact area between the microinjector and the membrane; however, it may move to the middle of the equilibrium configuration as the radius increases. To verify our model, some experiments were conducted on zebrafish egg cells. The results show that the computational analysis agrees with the experimental data, which supports the findings from the theoretical model. Copyright © 2013 Elsevier Ltd. All rights reserved.

Langmuir Probe Measurements in an Inductively Coupled Ar/CF4 Plasmas

NASA Technical Reports Server (NTRS)

Rao, M. V. V. S.; Meyyappan, M.; Sharma, S. P.; Arnold, James O. (Technical Monitor)

2000-01-01

Technological advancement in the microelectronics industry requires an understanding of the physical and chemical processes occurring in plasmas of fluorocarbon gases, such as carbon tetrafluoride (CF4) which is commonly used as an etchant, and their mixtures to optimize various operating parameters. In this paper we report data on electron number density (ne), electron temperature'(Te), electron energy distribution function (EEDF), mean electron energy, ion number density (ni), and plasma potential (Vp) measured by using Langmuir probe in an inductively coupled 13.56 MHz radio frequency plasmas generated in 50%Ar:50%CF4 mixture in the GEC cell. The probe data were recorded at various radial positions providing radial profiles of these plasma parameters at 10-50 mTorr pressures and 200 W and 300 W of RF power. Present measurements indicate that the electron and ion number densities increase with increase in pressure and power. Whereas the plasma potential and electron temperature decrease with increase in pressure, and they weakly depend on RF power. The radial profiles exhibit that the electron and ion number densities and the plasma potential peak at the center of the plasma with an exponential fall away from it, while the electron temperature has a minimum at the center and it increases steadily towards the electrode edge. The EEDFs have a characteristic drop near the low energy end at all pressures and pressures and their shapes represent non-Maxwellian plasma and exhibit more like Druyvesteyn energy distribution.v

Relative Sustainability of Natural Gas Assisted High-Octane Gasoline Blendstock Production from Biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Eric C; Zhang, Yi Min; Cai, Hao

Biomass-derived hydrocarbon fuel technologies are being developed and pursued for better economy, environment, and society benefits underpinning the sustainability of transportation energy. Increasing availability and affordability of natural gas (NG) in the US can play an important role in assisting renewable fuel technology development, primarily in terms of economic feasibility. When a biorefinery is co-processing NG with biomass, the current low cost of NG coupled with the higher NG carbon conversion efficiency potentially allow for cost competitiveness of the fuel while achieving a minimum GHG emission reduction of 50 percent or higher compared to petroleum fuel. This study evaluates themore » relative sustainability of the production of high-octane gasoline blendstock via indirect liquefaction (IDL) of biomass (and with NG co-feed) through methanol/dimethyl ether intermediates. The sustainability metrics considered in this study include minimum fuel selling price (MFSP), carbon conversion efficiency, life cycle GHG emissions, life cycle water consumption, fossil energy return on investment (EROI), GHG emission avoidance cost, and job creation. Co-processing NG can evidently improve the MFSP. Evaluation of the relative sustainability can shed light on the biomass-NG synergistic impacts and sustainability trade-offs associated with the IDL as high-octane gasoline blendstock production.« less

Phase inversion and frequency doubling of reflection high-energy electron diffraction intensity oscillations in the layer-by-layer growth of complex oxides

NASA Astrophysics Data System (ADS)

Mao, Zhangwen; Guo, Wei; Ji, Dianxiang; Zhang, Tianwei; Gu, Chenyi; Tang, Chao; Gu, Zhengbin; Nie*, Yuefeng; Pan, Xiaoqing

In situ reflection high-energy electron diffraction (RHEED) and its intensity oscillations are extremely important for the growth of epitaxial thin films with atomic precision. The RHEED intensity oscillations of complex oxides are, however, rather complicated and a general model is still lacking. Here, we report the unusual phase inversion and frequency doubling of RHEED intensity oscillations observed in the layer-by-layer growth of SrTiO3 using oxide molecular beam epitaxy. In contacts to the common understanding that the maximum(minimum) intensity occurs at SrO(TiO2) termination, respectively, we found that both maximum or minimum intensities can occur at SrO, TiO2, or even incomplete terminations depending on the incident angle of the electron beam, which raises a fundamental question if one can rely on the RHEED intensity oscillations to precisely control the growth of thin films. A general model including surface roughness and termination dependent mean inner potential qualitatively explains the observed phenomena, and provides the answer to the question how to prepare atomically and chemically precise surface/interfaces using RHEED oscillations for complex oxides. We thank National Basic Research Program of China (No. 11574135, 2015CB654901) and the National Thousand-Young-Talents Program.

Conformational analysis of (1. -->. 4)-. beta. -D-mannan triacetate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deslandes, Y.; Marchessault, R.H.; Bluhm, T.L.

1983-01-01

In wood, algae, and tubers, glucomannans have varying mannose-to-glucose ratios (M/G). Since diffraction on glucomannans of widely varying M/G do not show significant change in unit-cell base plane dimensions, the authors have suggested that isomorphous replacement may occur in glucomannans. To further investigate this point, it has been undertaken conformational analysis of glucomannan triacetate in which the X-ray fiber diagram suggests that two nonequivalent residues make up the asymmetric unit. X-ray fiber diagrams of the triacetate of glucomannan from Tubera salep show twofold symmetry along the chain axis with a fiber repeat of 1.6 nm. This implies that the asymmetricmore » unit is composed of two pyranose rings since the virtual bond length of a single pyranose ring cannot be greater than approximately 0.54 nm. By using empirical potential functions, it could be shown that the minimum internal energy of a mannan triacetate chain corresponds to a state where contiguous mannose triacetate units are not conformationally equivalent. This supports the hypothesis of mannobiose hexaacetate as the asymmetric unit. Furthermore, introduction of glucose triacetate into the backbone did not change the minimum energy conformation, thereby lending support to the isomorphous replacement concept in crystalline glucomannans. 19 references, 13 figures, 2 tables.« less

H2 cycling and microbial bioenergetics in anoxic sediments

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

The simple biochemistry of H2 is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, the great majority of microbial redox processes involve H2 as a reactant, product, or potential by-product, and the thermodynamics of these processes are thus highly sensitive to fluctuations in environmental H2 concentrations. In turn, H2 concentrations are controlled by the activity of H2-consuming microorganisms, which efficiently utilize this substrate down to levels which correspond to their bioenergetic limitations. Consequently, any environmental change which impacts the thermodynamics of H2-consuming organisms is mirrored by a corresponding change in H2 concentrations. This phenomenon is illustrated in anoxic sediments from Cape Lookout Bight, NC, USA: H2 concentrations are controlled by a suite of environmental parameters (e.g., temperature, sulfate concentrations) in a fashion which can be quantitatively described by a simple thermodynamic model. These findings allow us to calculate the apparent minimum quantity of biologically useful energy in situ. We find that sulfate reducing bacteria are not active at energy yields below -18 kJ per mole sulfate, while methanogenic archaea exhibit a minimum close to -10 kJ per mole methane.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albis, A.H.A.

This research effort is concerned with the identification and utilization of practical design guidelines to meet the demand for guidance in innovative planning and building design for Egyptian desert conditions. An energy-conscious design can be realized with a minimum expenditure of exhaustible energy resources and maximum utilization of the natural energies for cooling and heating. The energy design guidelines developed will be applied to an Urban Center, on a site selected to alleviate the stress on Cairo, which has been suffering for over two decades from housing shortages due to overpopulation. Design criteria to meet the challenges of this researchmore » include: neighborhood planning; orientation; building details; shading; colors of walls and roofs; materials; and massing configuration. In this research, desert construction and its aspects, use of building materials, approaches to energy conservation, and architectural principles for neighborhood planning are identified. The human requirement for thermal comfort specific to desert environments are analyzed and related to diurnal and annual patterns of outdoor conditions, and to the potential for modifying indoor thermal conditions by designs suitable to prevailing climatic conditions.« less

VizieR Online Data Catalog: Rate coefficients for H2(v,j)+H2(v',j'

NASA Astrophysics Data System (ADS)

Mandy, M. E.

2016-11-01

State-specific rate coefficients for the dissociation of H2 result of collisions with H2 were calculated for all combinations of (v,j) with an internal energy below 1eV. Full-dimensional quasiclassical trajectories were calculated using the BMKP2 interaction potential with a minimum of 80000 trajectories at each translational energy. Additional large batches of trajectories were carried out to calculate the cross sections near the threshold to dissociation to attain the desired precision of the rate coefficients. A piecewise linear excitation function was used to calculate the rate coefficient between 100 and 100000K. The resulting state-specific rate coefficients, γ, were parametrized as a function of temperature over the range 600-10000K using: log10γ(t)=a+bz+cz2-d(1/t-1) where t=T/4500K and z=log10t. The values of the resulting rate coefficients were sensitive to the internal energy of both molecules, with initial vibrational energy having a slightly greater effect than rotational energy. This effect diminished as temperature increased. (15 data files).

Building Energy Simulation Test for Existing Homes (BESTEST-EX) (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Judkoff, R.; Neymark, J.; Polly, B.

2011-12-01

This presentation discusses the goals of NREL Analysis Accuracy R&D; BESTEST-EX goals; what BESTEST-EX is; how it works; 'Building Physics' cases; 'Building Physics' reference results; 'utility bill calibration' cases; limitations and potential future work. Goals of NREL Analysis Accuracy R&D are: (1) Provide industry with the tools and technical information needed to improve the accuracy and consistency of analysis methods; (2) Reduce the risks associated with purchasing, financing, and selling energy efficiency upgrades; and (3) Enhance software and input collection methods considering impacts on accuracy, cost, and time of energy assessments. BESTEST-EX Goals are: (1) Test software predictions of retrofitmore » energy savings in existing homes; (2) Ensure building physics calculations and utility bill calibration procedures perform up to a minimum standard; and (3) Quantify impact of uncertainties in input audit data and occupant behavior. BESTEST-EX is a repeatable procedure that tests how well audit software predictions compare to the current state of the art in building energy simulation. There is no direct truth standard. However, reference software have been subjected to validation testing, including comparisons with empirical data.« less

Phase Transition to Exact Susy

NASA Astrophysics Data System (ADS)

Clavelli, L.

2007-04-01

The anthropic principle is based on the observation that, within narrow bounds, the laws of physics are such as to have allowed the evolution of life. The string theoretic approach to understanding this observation is based on the expectation that the effective potential has an enormous number of local minima with different particle masses and perhaps totally different fundamental couplings and space time topology. The vast majority of these alternative universes are totally inhospitable to life, having, for example, vacuum energies near the natural (Planck) scale. The statistics, however, are assumed to be such that a few of these local minima (and not more) have a low enough vacuum energy and suitable other properties to support life. In the inflationary era, the "multiverse" made successive transitions between the available minima until arriving at our current state of low vacuum energy. String theory, however, also suggests that the absolute minimum of the effective potential is exactly supersymmetric. Questions then arise as to why the inflationary era did not end by a transition to one of these, when will the universe make the phase transition to the exactly supersymmetric ground state, and what will be the properties of this final state.

Light-Ring Stability for Ultracompact Objects.

PubMed

Cunha, Pedro V P; Berti, Emanuele; Herdeiro, Carlos A R

2017-12-22

We prove the following theorem: axisymmetric, stationary solutions of the Einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a light ring) must have at least two light rings, and one of them is stable. It has been argued that stable light rings generally lead to nonlinear spacetime instabilities. Our result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. The proof of the theorem has two parts: (i) We show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. This result follows from a topological argument based on the Brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and, hence, it is applicable to any metric gravity theory where photons follow null geodesics. (ii) Assuming Einstein's equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition.

Light-Ring Stability for Ultracompact Objects

NASA Astrophysics Data System (ADS)

Cunha, Pedro V. P.; Berti, Emanuele; Herdeiro, Carlos A. R.

2017-12-01

We prove the following theorem: axisymmetric, stationary solutions of the Einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a light ring) must have at least two light rings, and one of them is stable. It has been argued that stable light rings generally lead to nonlinear spacetime instabilities. Our result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. The proof of the theorem has two parts: (i) We show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. This result follows from a topological argument based on the Brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and, hence, it is applicable to any metric gravity theory where photons follow null geodesics. (ii) Assuming Einstein's equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition.

Field gradients can control the alignment of nanorods.

PubMed

Ooi, Chinchun; Yellen, Benjamin B

2008-08-19

This work is motivated by the unexpected experimental observation that field gradients can control the alignment of nonmagnetic nanorods immersed inside magnetic fluids. In the presence of local field gradients, nanorods were observed to align perpendicular to the external field at low field strengths, but parallel to the external field at high field strengths. The switching behavior results from the competition between a preference to align with the external field (orientational potential energy) and preference to move into regions of minimum magnetic field (positional potential energy). A theoretical model is developed to explain this experimental behavior by investigating the statistics of nanorod alignment as a function of both the external uniform magnetic field strength and the local magnetic field variation above a periodic array of micromagnets. Computational phase diagrams are developed which indicate that the relative population of nanorods in parallel and perpendicular states can be adjusted through several control parameters. However, an energy barrier to rotation was discovered to influence the rate kinetics and restrict the utility of this assembly technique to nanorods which are slightly shorter than the micromagnet length. Experimental results concerning the orientation of nanorods inside magnetic fluid are also presented and shown to be in strong agreement with the theoretical work.

Building Better: Advanced Energy Design Guides - Continuum Magazine |

Science.gov Websites

NREL Building Better: Advanced Energy Design Guides Building Better: Advanced Energy Design Greensburg be constructed to meet Leadership in Energy and Environmental Design (LEED) Platinum ratings from design needs to incorporate a number of recommendations for achieving energy savings over the minimum

Isometric deformations of unstretchable material surfaces, a spatial variational treatment

NASA Astrophysics Data System (ADS)

Chen, Yi-Chao; Fosdick, Roger; Fried, Eliot

2018-07-01

The stored energy of an unstretchable material surface is assumed to depend only upon the curvature tensor. By control of its edge(s), the surface is deformed isometrically from its planar undistorted reference configuration into an equilibrium shape. That shape is to be determined from a suitably constrained variational problem as a state of relative minimal potential energy. We pose the variational problem as one of relative minimum potential energy in a spatial form, wherein the deformation of a flat, undistorted region D in E2 to its distorted form S in E3 is assumed specified. We then apply the principle that the first variation of the potential energy, expressed as a functional over S ∪ ∂S , must vanish for all admissible variations that correspond to isometric deformations from the distorted configuration S and that also contain the essence of flatness that characterizes the reference configuration D , but is not covered by the single statement that the variation of S correspond to an isometric deformation. We emphasize the commonly overlooked condition that the spatial expression of the variational problem requires an additional variational constraint of zero Gaussian curvature to ensure that variations from S that are isometric deformations also contain the notion of flatness. In this context, it is particularly revealing to observe that the two constraints produce distinct, but essential and complementary, conditions on the first variation of S. The resulting first variation integral condition, together with the constraints, may be applied, for example, to the case of a flat, undistorted, rectangular strip D that is deformed isometrically into a closed ring S by connecting its short edges and specifying that its long edges are free of loading and, therefore, subject to zero traction and couple traction. The elementary example of a closed ring without twist as a state of relative minimum potential energy is discussed in detail, and the bending of the strip by opposing specific bending moments on its short edges is treated as a particular case. Finally, the constrained variational problem, with the introduction of appropriate constraint reactions as Lagrangian multipliers to account for the requirements that the deformation from D to S is isometric and that D is flat, is formulated in the spatial form, and the associated Euler-Lagrange equations are derived. We then solve the Euler-Lagrange equations for two representative problems in which a planar undistorted rectangular material strip is isometrically deformed by applied edge tractions and couple tractions (i.e., specific edge moments) into (i) a bent and twisted circular cylindrical helical state, and (ii) a state conformal with the surface of a right circular conical form.

Dehydrogenation of benzene on Pt(111) surface

NASA Astrophysics Data System (ADS)

Gao, W.; Zheng, W. T.; Jiang, Q.

2008-10-01

The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

Dehydrogenation of benzene on Pt(111) surface.

PubMed

Gao, W; Zheng, W T; Jiang, Q

2008-10-28

The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

Wing flapping with minimum energy. [minimize the drag for a bending moment at the wing root

NASA Technical Reports Server (NTRS)

Jones, R. T.

1980-01-01

For slow flapping motions it is found that the minimum energy loss occurs when the vortex wake moves as a rigid surface that rotates about the wing root - a condition analogous to that determined for a slow-turning propeller. The optimum circulation distribution determined by this condition differs from the elliptic distribution, showing a greater concentration of lift toward the tips. It appears that very high propulsive efficiencies are obtained by flapping.

From brittle to ductile fracture in disordered materials.

PubMed

Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

2010-10-08

We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

Planning Minimum-Energy Paths in an Off-Road Environment with Anisotropic Traversal Costs and Motion Constraints

DTIC Science & Technology

1989-06-01

problems, and (3) weighted-region problems. Since the minimum-energy path-planning problem addressed in this dissertation is a hybrid between the two...contains components that are strictly vehicle dependent, components that are strictly terrain dependent, and components representing a hybrid of...Single Segment Braking/Multiple Segment Hybrid Using Eq. (3.46), the traversal cost U 1,.-1 can be rewritten as Uop- 1 = mgD Itan01 , (4.12a) and the

[The principle of the energy minimum in ontogeny and the channeling of developmental processes].

PubMed

Ozerniuk, N D

1989-01-01

The principle of minimum of energy in ontogenesis has been formulated on the basis of data concerning age changes in energetic metabolism, as well as the influence of ecological factors on this process. According to this principle the smallest expenditures of energy are observed in the zone of the most favorable developmental conditions. The minimal level of energetic metabolism at every developmental stage that corresponds to the most stable state of organism is treated as homeostasis and the developmental stability is treated as homeorrhesis. Regulation mechanisms of energetic metabolism during ontogenesis and under the influence of environmental factors are analyzed.

On the v-representability of ensemble densities of electron systems

NASA Astrophysics Data System (ADS)

Gonis, A.; Däne, M.

2018-05-01

Analogously to the case at zero temperature, where the density of the ground state of an interacting many-particle system determines uniquely (within an arbitrary additive constant) the external potential acting on the system, the thermal average of the density over an ensemble defined by the Boltzmann distribution at the minimum of the thermodynamic potential, or the free energy, determines the external potential uniquely (and not just modulo a constant) acting on a system described by this thermodynamic potential or free energy. The paper describes a formal procedure that generates the domain of a constrained search over general ensembles (at zero or elevated temperatures) that lead to a given density, including as a special case a density thermally averaged at a given temperature, and in the case of a v-representable density determines the external potential leading to the ensemble density. As an immediate consequence of the general formalism, the concept of v-representability is extended beyond the hitherto discussed case of ground state densities to encompass excited states as well. Specific application to thermally averaged densities solves the v-representability problem in connection with the Mermin functional in a manner analogous to that in which this problem was recently settled with respect to the Hohenberg and Kohn functional. The main formalism is illustrated with numerical results for ensembles of one-dimensional, non-interacting systems of particles under a harmonic potential.

On the v-representability of ensemble densities of electron systems

DOE PAGES

Gonis, A.; Dane, M.

2017-12-30

Analogously to the case at zero temperature, where the density of the ground state of an interacting many-particle system determines uniquely (within an arbitrary additive constant) the external potential acting on the system, the thermal average of the density over an ensemble defined by the Boltzmann distribution at the minimum of the thermodynamic potential, or the free energy, determines the external potential uniquely (and not just modulo a constant) acting on a system described by this thermodynamic potential or free energy. The study describes a formal procedure that generates the domain of a constrained search over general ensembles (at zeromore » or elevated temperatures) that lead to a given density, including as a special case a density thermally averaged at a given temperature, and in the case of a v-representable density determines the external potential leading to the ensemble density. As an immediate consequence of the general formalism, the concept of v-representability is extended beyond the hitherto discussed case of ground state densities to encompass excited states as well. Specific application to thermally averaged densities solves the v-representability problem in connection with the Mermin functional in a manner analogous to that in which this problem was recently settled with respect to the Hohenberg and Kohn functional. Finally, the main formalism is illustrated with numerical results for ensembles of one-dimensional, non-interacting systems of particles under a harmonic potential.« less

Home | BEopt

Science.gov Websites

BEopt - Building Energy Optimization BEopt NREL - National Renewable Energy Laboratory Primary Energy Optimization) software provides capabilities to evaluate residential building designs and identify sequential search optimization technique used by BEopt: Finds minimum-cost building designs at different

Why Is Benzene Unique? Screening Magnetic Properties of C6 H6 Isomers.

PubMed

Janda, Tomáš; Foroutan-Nejad, Cina

2018-05-25

Magnetic properties are commonly used to identify new aromatic molecules because it is generally believed that magnetization and energetic stability are correlated. To verify the potential correlation between the energy and magnetic response properties, we examined a set of 198 isomers of C 6 H 6 . The energy and magnetic properties of these molecules can be directly compared with no need to invoke any arbitrary reference state because the studied systems are all isomers. Benzene is the global minimum on the potential energy surface of C 6 H 6 , 35 kcal mol -1 lower in energy than the second most stable isomer, fulvene. Unlike its electronic energy, isotropic magnetizability of benzene is slightly lower than the average magnetizability of its isomers. Altogether, 44 isomers of C 6 H 6 were identified to have more negative magnetic susceptibility than benzene but were between 67.0 to 168.6 kcal mol -1 higher in energy than benzene. However, benzene is unique in two ways. Analyzing the paramagnetic contribution to the magnetic susceptibility as originally suggested by Bilde and Hansen (Mol. Phys., 1997, 92, 237) revealed that 53 molecules have lower paramagnetic susceptibility than benzene but among monocyclic systems benzene has the least paramagnetic susceptibility. Furthermore, benzene has the largest out-of-plane magnetic susceptibility that originates from the strongest ring current among all studied species. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamic Performance and Cost Optimization of a Novel Hybrid Thermal-Compressed Air Energy Storage System Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houssainy, Sammy; Janbozorgi, Mohammad; Kavehpour, Pirouz

Compressed Air Energy Storage (CAES) can potentially allow renewable energy sources to meet electricity demands as reliably as coal-fired power plants. However, conventional CAES systems rely on the combustion of natural gas, require large storage volumes, and operate at high pressures, which possess inherent problems such as high costs, strict geological locations, and the production of greenhouse gas emissions. A novel and patented hybrid thermal-compressed air energy storage (HT-CAES) design is presented which allows a portion of the available energy, from the grid or renewable sources, to operate a compressor and the remainder to be converted and stored in themore » form of heat, through joule heating in a sensible thermal storage medium. The HT-CAES design incudes a turbocharger unit that provides supplementary mass flow rate alongside the air storage. The hybrid design and the addition of a turbocharger have the beneficial effect of mitigating the shortcomings of conventional CAES systems and its derivatives by eliminating combustion emissions and reducing storage volumes, operating pressures, and costs. Storage efficiency and cost are the two key factors, which upon integration with renewable energies would allow the sources to operate as independent forms of sustainable energy. The potential of the HT-CAES design is illustrated through a thermodynamic optimization study, which outlines key variables that have a major impact on the performance and economics of the storage system. The optimization analysis quantifies the required distribution of energy between thermal and compressed air energy storage, for maximum efficiency, and for minimum cost. This study provides a roundtrip energy and exergy efficiency map of the storage system and illustrates a trade off that exists between its capital cost and performance.« less

Improving an Assessment of Tidal Stream Energy Resource for Anchorage, Alaska

NASA Astrophysics Data System (ADS)

Xu, T.; Haas, K. A.

2016-12-01

Increasing global energy demand is driving the pursuit of new and innovative energy sources leading to the need for assessing and utilizing alternative, productive and reliable energy resources. Tidal currents, characterized by periodicity and predictability, have long been explored and studied as a potential energy source, focusing on many different locations with significant tidal ranges. However, a proper resource assessment cannot be accomplished without accurate knowledge of the spatial-temporal distribution and availability of tidal currents. Known for possessing one of the top tidal energy sources along the U.S. coastline, Cook Inlet, Alaska is the area of interest for this project. A previous regional scaled resource assessment has been completed, however, the present study is to focus the assessment on the available power specifically near Anchorage while significantly improving the accuracy of the assessment following IEC guidelines. The Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system is configured to simulate the tidal flows with grid refinement techniques for a minimum of 32 days, encompassing an entire lunar cycle. Simulation results are validated by extracting tidal constituents with harmonic analysis and comparing tidal components with National Oceanic and Atmospheric Administration (NOAA) observations and predictions. Model calibration includes adjustments to bottom friction coefficients and the usage of different tidal database. Differences between NOAA observations and COAWST simulations after applying grid refinement decrease, compared with results from a former study without grid refinement. Also, energy extraction is simulated at potential sites to study the impact on the tidal resources. This study demonstrates the enhancement of the resource assessment using grid refinement to evaluate tidal energy near Anchorage within Cook Inlet, Alaska, the productivity that energy extraction can achieve and the change in tidal currents caused by energy extraction.

Exchange-Hole Dipole Dispersion Model for Accurate Energy Ranking in Molecular Crystal Structure Prediction II: Nonplanar Molecules.

PubMed

Whittleton, Sarah R; Otero-de-la-Roza, A; Johnson, Erin R

2017-11-14

The crystal structure prediction (CSP) of a given compound from its molecular diagram is a fundamental challenge in computational chemistry with implications in relevant technological fields. A key component of CSP is the method to calculate the lattice energy of a crystal, which allows the ranking of candidate structures. This work is the second part of our investigation to assess the potential of the exchange-hole dipole moment (XDM) dispersion model for crystal structure prediction. In this article, we study the relatively large, nonplanar, mostly flexible molecules in the first five blind tests held by the Cambridge Crystallographic Data Centre. Four of the seven experimental structures are predicted as the energy minimum, and thermal effects are demonstrated to have a large impact on the ranking of at least another compound. As in the first part of this series, delocalization error affects the results for a single crystal (compound X), in this case by detrimentally overstabilizing the π-conjugated conformation of the monomer. Overall, B86bPBE-XDM correctly predicts 16 of the 21 compounds in the five blind tests, a result similar to the one obtained using the best CSP method available to date (dispersion-corrected PW91 by Neumann et al.). Perhaps more importantly, the systems for which B86bPBE-XDM fails to predict the experimental structure as the energy minimum are mostly the same as with Neumann's method, which suggests that similar difficulties (absence of vibrational free energy corrections, delocalization error,...) are not limited to B86bPBE-XDM but affect GGA-based DFT-methods in general. Our work confirms B86bPBE-XDM as an excellent option for crystal energy ranking in CSP and offers a guide to identify crystals (organic salts, conjugated flexible systems) where difficulties may appear.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, H; Guerrero, M; Prado, K

Purpose: Building up a TG-71 based electron monitor-unit (MU) calculation protocol usually involves massive measurements. This work investigates a minimum data set of measurements and its calculation accuracy and measurement time. Methods: For 6, 9, 12, 16, and 20 MeV of our Varian Clinac-Series linear accelerators, the complete measurements were performed at different depth using 5 square applicators (6, 10, 15, 20 and 25 cm) with different cutouts (2, 3, 4, 6, 10, 15 and 20 cm up to applicator size) for 5 different SSD’s. For each energy, there were 8 PDD scans and 150 point measurements for applicator factors,more » cutout factors and effective SSDs that were then converted to air-gap factors for SSD 99–110cm. The dependence of each dosimetric quantity on field size and SSD was examined to determine the minimum data set of measurements as a subset of the complete measurements. The “missing” data excluded in the minimum data set were approximated by linear or polynomial fitting functions based on the included data. The total measurement time and the calculated electron MU using the minimum and the complete data sets were compared. Results: The minimum data set includes 4 or 5 PDD’s and 51 to 66 point measurements for each electron energy, and more PDD’s and fewer point measurements are generally needed as energy increases. Using only <50% of complete measurement time, the minimum data set generates acceptable MU calculation results compared to those with the complete data set. The PDD difference is within 1 mm and the calculated MU difference is less than 1.5%. Conclusion: Data set measurement for TG-71 electron MU calculations can be minimized based on the knowledge of how each dosimetric quantity depends on various setup parameters. The suggested minimum data set allows acceptable MU calculation accuracy and shortens measurement time by a few hours.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chen; Perez, Danny; Voter, Arthur F.

Hyperdynamics is a powerful method to significantly extend the time scales amenable to molecular dynamics simulation of infrequent events. One outstanding challenge, however, is the development of the so-called bias potential required by the method. In this work, we design a bias potential using information about all minimum energy pathways (MEPs) out of the current state. While this approach is not suitable for use in an actual hyperdynamics simulation, because the pathways are generally not known in advance, it allows us to show that it is possible to come very close to the theoretical boost limit of hyperdynamics while maintainingmore » high accuracy. We demonstrate this by applying this MEP-based hyperdynamics (MEP-HD) to metallic surface diffusion systems. In most cases, MEP-HD gives boost factors that are orders of magnitude larger than the best existing bias potential, indicating that further development of hyperdynamics bias potentials could have a significant payoff. Lastly, we discuss potential practical uses of MEP-HD, including the possibility of developing MEP-HD into a true hyperdynamics.« less

Relaxation of exciton and photoinduced dimerization in crystalline C60

NASA Astrophysics Data System (ADS)

Suzuki, Masato; Iida, Takeshi; Nasu, Keiichiro

2000-01-01

We numerically investigate the lattice relaxation of photogenerated exciton in crystalline C60 so as to clarify the mechanism of the photoinduced dimerization processes in this material. In our theory, we deal with the π electrons together with the interatomic effective potentials. Calculations are mainly based on the mean-field theory for interelectron interactions but are also reinforced by taking the electron-hole correlation into account, so that we can obtain the exciton effect. Using a cluster model, we calculate the adiabatic potential energy surfaces of the excitons relevant to the photoinduced dimerization processes occurring in a face-centered-cubic crystal of C60. The potential surfaces of the Frenkel excitons turned out to be quite uneven with several energy minimum points during the structural changes from the Franck-Condon state to the dimerized state. This leads to the conclusion that various structural defects exist at low temperatures even in the single crystal, as an intrinsic property of this molecular crystal with a complicated intermolecular interaction. From the analysis of the potential surfaces of the charge-transfer (CT) excitons, it is confirmed that the CT exciton relaxes down to its self-trapped state, wherein the adjacent two molecules get close together. This implies that the CT between adjacent two molecules is one of mechanisms that triggers the photodimerization or the photopolymerization. The oscillator strength distributions are also calculated for various intermediate structures along the lattice relaxation path. As the dimerization reaction proceeds, the oscillator strength grows in the energy region below the fundamental absorption edge, and the lowest-energy peak, originally at about 1.9 eV, finally shifts down to about 1.7 eV in the final dimerized structure. These results clarify the electronic origins of the luminescence observed in the C60 single crystal. Moreover, the origins of the photoinduced absorption spectra observed by Bazhenov, Gorbunov, and Volkodav are elucidated by characteristics of the adiabatic potential energy surfaces obtained here.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, P.; Purdue University, West Lafayette, Indiana 47907; Verma, K.

Borazine is isoelectronic with benzene and is popularly referred to as inorganic benzene. The study of non-covalent interactions with borazine and comparison with its organic counterpart promises to show interesting similarities and differences. The motivation of the present study of the borazine-water interaction, for the first time, stems from such interesting possibilities. Hydrogen-bonded complexes of borazine and water were studied using matrix isolation infrared spectroscopy and quantum chemical calculations. Computations were performed at M06-2X and MP2 levels of theory using 6-311++G(d,p) and aug-cc-pVDZ basis sets. At both the levels of theory, the complex involving an N–H⋯O interaction, where the N–Hmore » of borazine serves as the proton donor to the oxygen of water was found to be the global minimum, in contrast to the benzene-water system, which showed an H–π interaction. The experimentally observed infrared spectra of the complexes corroborated well with our computations for the complex corresponding to the global minimum. In addition to the global minimum, our computations also located two local minima on the borazine-water potential energy surface. Of the two local minima, one corresponded to a structure where the water was the proton donor to the nitrogen of borazine, approaching the borazine ring from above the plane of the ring; a structure that resembled the global minimum in the benzene-water H–π complex. The second local minimum corresponded to an interaction of the oxygen of water with the boron of borazine, which can be termed as the boron bond. Clearly the borazine-water system presents a richer landscape than the benzene-water system.« less

Minimum Energy of Multicomponent Distillation Systems Using Minimum Additional Heat and Mass Integration Sections

DOE PAGES

Jiang, Zheyu; Ramapriya, Gautham Madenoor; Tawarmalani, Mohit; ...

2018-04-20

Heat and mass integration to consolidate distillation columns in a multicomponent distillation configuration can lead to a number of new energy efficient and cost effective configurations. In this paper, we identify a powerful and simple-to-use fact about heat and mass integration. The newly developed heat and mass integrated configurations, which we call as HMP configurations, involve first introducing thermal couplings to all intermediate transfer streams, followed by consolidating columns associated with a lighter pure product reboiler and a heavier pure product condenser. A systematic method of enumerating all HMP configurations is introduced. We compare the energy savings of HMP configurationsmore » with the well-known fully thermally coupled (FTC) configurations. We demonstrate that HMP configurations can have very similar and sometimes even the same minimum total vapor duty requirement as the FTC configuration, while using far less number of column sections, intermediate transfer streams, and thermal couplings than the FTC configurations.« less

Minimum Energy of Multicomponent Distillation Systems Using Minimum Additional Heat and Mass Integration Sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Zheyu; Ramapriya, Gautham Madenoor; Tawarmalani, Mohit

Heat and mass integration to consolidate distillation columns in a multicomponent distillation configuration can lead to a number of new energy efficient and cost effective configurations. In this paper, we identify a powerful and simple-to-use fact about heat and mass integration. The newly developed heat and mass integrated configurations, which we call as HMP configurations, involve first introducing thermal couplings to all intermediate transfer streams, followed by consolidating columns associated with a lighter pure product reboiler and a heavier pure product condenser. A systematic method of enumerating all HMP configurations is introduced. We compare the energy savings of HMP configurationsmore » with the well-known fully thermally coupled (FTC) configurations. We demonstrate that HMP configurations can have very similar and sometimes even the same minimum total vapor duty requirement as the FTC configuration, while using far less number of column sections, intermediate transfer streams, and thermal couplings than the FTC configurations.« less

Mechanisms contributing to seasonal homeostasis of minimum leaf water potential and predawn disequilibrium between soil and plant water potential in Neotropical savanna trees.

Treesearch

Sandra J. Bucci; Guillermo Goldstein; Frederick C. Meinzer; Augusto C. Franco; Paula Campanello; Fabián G. Scholz

2005-01-01

Seasonal regulation of leaf water potential (ΨL) was studied in eight dominant woody savanna species growing in Brazilian savanna (Cerrado) sites that experience a 5-month dry season. Despite marked seasonal variation in precipitation and air saturation deficit (D), seasonal differences in midday minimum Ψ...

Evolved Minimal Frustration in Multifunctional Biomolecules.

PubMed

Röder, Konstantin; Wales, David J

2018-05-25

Protein folding is often viewed in terms of a funnelled potential or free energy landscape. A variety of experiments now indicate the existence of multifunnel landscapes, associated with multifunctional biomolecules. Here, we present evidence that these systems have evolved to exhibit the minimal number of funnels required to fulfil their cellular functions, suggesting an extension to the principle of minimum frustration. We find that minimal disruptive mutations result in additional funnels, and the associated structural ensembles become more diverse. The same trends are observed in an atomic cluster. These observations suggest guidelines for rational design of engineered multifunctional biomolecules.

Bragg x-ray survey spectrometer for ITER.

PubMed

Varshney, S K; Barnsley, R; O'Mullane, M G; Jakhar, S

2012-10-01

Several potential impurity ions in the ITER plasmas will lead to loss of confined energy through line and continuum emission. For real time monitoring of impurities, a seven channel Bragg x-ray spectrometer (XRCS survey) is considered. This paper presents design and analysis of the spectrometer, including x-ray tracing by the Shadow-XOP code, sensitivity calculations for reference H-mode plasma and neutronics assessment. The XRCS survey performance analysis shows that the ITER measurement requirements of impurity monitoring in 10 ms integration time at the minimum levels for low-Z to high-Z impurity ions can largely be met.

Fermion localization on a split brane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chumbes, A. E. R.; Vasquez, A. E. O.; Hott, M. B.

2011-05-15

In this work we analyze the localization of fermions on a brane embedded in five-dimensional, warped and nonwarped, space-time. In both cases we use the same nonlinear theoretical model with a nonpolynomial potential featuring a self-interacting scalar field whose minimum energy solution is a soliton (a kink) which can be continuously deformed into a two-kink. Thus a single brane splits into two branes. The behavior of spin 1/2 fermions wave functions on the split brane depends on the coupling of fermions to the scalar field and on the geometry of the space-time.

Motor Controller

NASA Technical Reports Server (NTRS)

1988-01-01

M.H. Marks Enterprises' Power Factor Controller (PFC) matches voltage with motor's actual need. Plugged into a motor, PFC continuously determines motor load by sensing shifts between voltage and current flow. When it senses a light load, it cuts voltage to the minimum needed. It offers potential energy savings ranging from eight percent up to 65 percent depending on the application. Myles Marks started out with the notion of writing an article for Popular Electronics magazine at the same time offering to furnish kits to readers interested in assembling PFC's. Within two weeks from publication he had orders for 500 kits and orders are still coming three years later.

The C4H7+ cation. A theoretical investigation

NASA Technical Reports Server (NTRS)

Koch, W.; Liu, B.; DeFrees, D. J.

1988-01-01

The potential energy surface of the C4H7+ cation has been investigated with ab initio quantum chemical theory. Extended basis set calculations, including electronic correlation, show that cyclobutyl and cyclopropylcarbinyl cation are equally stable isomers. The saddle point connecting these isomers lies 0.6 kcal/mol above the minima. The global C4H7+ minimum corresponds to the 1-methylallyl cation, which is 9.0 kcal/mol more stable than the cyclobutyl and the cyclopropylcarbinyl cation and 9.5 kcal/mol below the 2-methylallyl cation. These results are in excellent agreement with experimental data.

Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes

DOE PAGES

Jackson, Nicholas E.; Brettmann, Blair K.; Vishwanath, Venkatram; ...

2017-02-03

Here, coarse-grained molecular dynamics enhanced by free-energy sampling methods is used to examine the roles of solvophobicity and multivalent salts on polyelectrolyte brush collapse. Specifically, we demonstrate that while ostensibly similar, solvophobic collapsed brushes and multivalent-ion collapsed brushes exhibit distinct mechanistic and structural features. Notably, multivalent-induced heterogeneous brush collapse is observed under good solvent polymer backbone conditions, demonstrating that the mechanism of multivalent collapse is not contingent upon a solvophobic backbone. Umbrella sampling of the potential of mean-force (PMF) between two individual brush strands confirms this analysis, revealing starkly different PMFs under solvophobic and multivalent conditions, suggesting the role ofmore » multivalent “bridging” as the discriminating feature in trivalent collapse. Structurally, multivalent ions show a propensity for nucleating order within collapsed brushes, whereas poor-solvent collapsed brushes are more disordered; this difference is traced to the existence of a metastable PMF minimum for poor solvent conditions, and a global PMF minimum for trivalent systems, under experimentally relevant conditions.« less

Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Nicholas E.; Brettmann, Blair K.; Vishwanath, Venkatram

Here, coarse-grained molecular dynamics enhanced by free-energy sampling methods is used to examine the roles of solvophobicity and multivalent salts on polyelectrolyte brush collapse. Specifically, we demonstrate that while ostensibly similar, solvophobic collapsed brushes and multivalent-ion collapsed brushes exhibit distinct mechanistic and structural features. Notably, multivalent-induced heterogeneous brush collapse is observed under good solvent polymer backbone conditions, demonstrating that the mechanism of multivalent collapse is not contingent upon a solvophobic backbone. Umbrella sampling of the potential of mean-force (PMF) between two individual brush strands confirms this analysis, revealing starkly different PMFs under solvophobic and multivalent conditions, suggesting the role ofmore » multivalent “bridging” as the discriminating feature in trivalent collapse. Structurally, multivalent ions show a propensity for nucleating order within collapsed brushes, whereas poor-solvent collapsed brushes are more disordered; this difference is traced to the existence of a metastable PMF minimum for poor solvent conditions, and a global PMF minimum for trivalent systems, under experimentally relevant conditions.« less

Computational Role of Tunneling in a Programmable Quantum Annealer

NASA Technical Reports Server (NTRS)

Boixo, Sergio; Smelyanskiy, Vadim; Shabani, Alireza; Isakov, Sergei V.; Dykman, Mark; Amin, Mohammad; Mohseni, Masoud; Denchev, Vasil S.; Neven, Hartmut

2016-01-01

Quantum tunneling is a phenomenon in which a quantum state tunnels through energy barriers above the energy of the state itself. Tunneling has been hypothesized as an advantageous physical resource for optimization. Here we present the first experimental evidence of a computational role of multiqubit quantum tunneling in the evolution of a programmable quantum annealer. We developed a theoretical model based on a NIBA Quantum Master Equation to describe the multi-qubit dissipative cotunneling effects under the complex noise characteristics of such quantum devices.We start by considering a computational primitive, the simplest non-convex optimization problem consisting of just one global and one local minimum. The quantum evolutions enable tunneling to the global minimum while the corresponding classical paths are trapped in a false minimum. In our study the non-convex potentials are realized by frustrated networks of qubit clusters with strong intra-cluster coupling. We show that the collective effect of the quantum environment is suppressed in the critical phase during the evolution where quantum tunneling decides the right path to solution. In a later stage dissipation facilitates the multiqubit cotunneling leading to the solution state. The predictions of the model accurately describe the experimental data from the D-WaveII quantum annealer at NASA Ames. In our computational primitive the temperature dependence of the probability of success in the quantum model is opposite to that of the classical paths with thermal hopping. Specially, we provide an analysis of an optimization problem with sixteen qubits,demonstrating eight qubit cotunneling that increases success probabilities. Furthermore, we report results for larger problems with up to 200 qubits that contain the primitive as subproblems.

How do minimum cigarette price laws affect cigarette prices at the retail level?

PubMed Central

Feighery, E; Ribisl, K; Schleicher, N; Zellers, L; Wellington, N

2005-01-01

Objectives: Half of US states have minimum cigarette price laws that were originally passed to protect small independent retailers from unfair price competition with larger retailers. These laws prohibit cigarettes from being sold below a minimum price that is set by a formula. Many of these laws allow cigarette company promotional incentives offered to retailers, such as buydowns and master-type programmes, to be calculated into the formula. Allowing this provision has the potential to lower the allowable minimum price. This study assesses whether stores in states with minimum price laws have higher cigarette prices and lower rates of retailer participation in cigarette company promotional incentive programmes. Design: Retail cigarette prices and retailer participation in cigarette company incentive programmes in 2001 were compared in eight states with minimum price laws and seven states without them. New York State had the most stringent minimum price law at the time of the study because it excluded promotional incentive programmes in its price setting formula; cigarette prices in New York were compared to all other states included in the study. Results: Cigarette prices were not significantly different in our sample of US states with and without cigarette minimum price laws. Cigarette prices were significantly higher in New York stores than in the 14 other states combined. Conclusions: Most existing minimum cigarette price laws appear to have little impact on the retail price of cigarettes. This may be because they allow the use of promotional programmes, which are used by manufacturers to reduce cigarette prices. New York's strategy to disallow these types of incentive programmes may result in higher minimum cigarette prices, and should also be explored as a potential policy strategy to control cigarette company marketing practices in stores. Strict cigarette minimum price laws may have the potential to reduce cigarette consumption by decreasing demand through increased cigarette prices and reduced promotional activities at retail outlets. PMID:15791016

How do minimum cigarette price laws affect cigarette prices at the retail level?

PubMed

Feighery, E C; Ribisl, K M; Schleicher, N C; Zellers, L; Wellington, N

2005-04-01

Half of US states have minimum cigarette price laws that were originally passed to protect small independent retailers from unfair price competition with larger retailers. These laws prohibit cigarettes from being sold below a minimum price that is set by a formula. Many of these laws allow cigarette company promotional incentives offered to retailers, such as buydowns and master-type programmes, to be calculated into the formula. Allowing this provision has the potential to lower the allowable minimum price. This study assesses whether stores in states with minimum price laws have higher cigarette prices and lower rates of retailer participation in cigarette company promotional incentive programmes. Retail cigarette prices and retailer participation in cigarette company incentive programmes in 2001 were compared in eight states with minimum price laws and seven states without them. New York State had the most stringent minimum price law at the time of the study because it excluded promotional incentive programmes in its price setting formula; cigarette prices in New York were compared to all other states included in the study. Cigarette prices were not significantly different in our sample of US states with and without cigarette minimum price laws. Cigarette prices were significantly higher in New York stores than in the 14 other states combined. Most existing minimum cigarette price laws appear to have little impact on the retail price of cigarettes. This may be because they allow the use of promotional programmes, which are used by manufacturers to reduce cigarette prices. New York's strategy to disallow these types of incentive programmes may result in higher minimum cigarette prices, and should also be explored as a potential policy strategy to control cigarette company marketing practices in stores. Strict cigarette minimum price laws may have the potential to reduce cigarette consumption by decreasing demand through increased cigarette prices and reduced promotional activities at retail outlets.

10 CFR 501.50 - Policy.

Code of Federal Regulations, 2014 CFR

2014-01-01

... energy source or in amounts in excess of the minimum amount necessary to maintain reliability of... 10 Energy 4 2014-01-01 2014-01-01 false Policy. 501.50 Section 501.50 Energy DEPARTMENT OF ENERGY (CONTINUED) ALTERNATE FUELS ADMINISTRATIVE PROCEDURES AND SANCTIONS Prohibition Rules and Orders § 501.50...

10 CFR 501.50 - Policy.

Code of Federal Regulations, 2013 CFR

2013-01-01

... energy source or in amounts in excess of the minimum amount necessary to maintain reliability of... 10 Energy 4 2013-01-01 2013-01-01 false Policy. 501.50 Section 501.50 Energy DEPARTMENT OF ENERGY (CONTINUED) ALTERNATE FUELS ADMINISTRATIVE PROCEDURES AND SANCTIONS Prohibition Rules and Orders § 501.50...

Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period

NASA Technical Reports Server (NTRS)

Lave, K. A.; Wiedenbeck, Mark E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Israel, M. H..; Leske, R. A.; Mewaldt, R. A.;

Investigating the Sensitivity of Model Intraseasonal Variability to Minimum Entrainment

NASA Astrophysics Data System (ADS)

Hannah, W. M.; Maloney, E. D.

2008-12-01

Previous studies have shown that using a Relaxed Arakawa-Schubert (RAS) convective parameterization with appropriate convective triggers and assumptions about rain re-evaporation produces realistic intraseasonal variability. RAS represents convection with an ensemble of clouds detraining at different heights, each with different entrainment rate, the highest clouds having the lowest entrainment rates. If tropospheric temperature gradients are weak and boundary layer moist static energy is relatively constant, then by limiting the minimum entrainment rate deep convection is suppressed in the presence of dry tropospheric air. This allows moist static energy to accumulate and be discharged during strong intraseasonal convective events, which is consistent with the discharge/recharge paradigm. This study will examine the sensitivity of intra-seasonal variability to changes in minimum entrainment rate in the NCAR-CAM3 with the RAS scheme. Simulations using several minimum entrainment rate thresholds will be investigated. A frequency-wavenumber analysis will show the improvement of the MJO signal as minimum entrainment rate is increased. The spatial and vertical structure of MJO-like disturbances will be examined, including an analysis of the time evolution of vertical humidity distribution for each simulation. Simulated results will be compared to observed MJO events in NCEP-1 reanalysis and CMAP precipitation.

Dual Energy Method for Breast Imaging: A Simulation Study.

PubMed

Koukou, V; Martini, N; Michail, C; Sotiropoulou, P; Fountzoula, C; Kalyvas, N; Kandarakis, I; Nikiforidis, G; Fountos, G

2015-01-01

Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in order to overcome the limited kVp range of mammographic units used in previous DE studies, combined with a high resolution CMOS sensor (pixel size of 22.5 μm) for improved resolution. Various filter materials were examined based on their K-absorption edge. Hydroxyapatite (HAp) was used to simulate microcalcifications. The contrast to noise ratio (CNR tc ) of the subtracted images was calculated for both monoenergetic and polyenergetic X-ray beams. The optimum monoenergetic pair was 23/58 keV for the low and high energy, respectively, resulting in a minimum detectable microcalcification thickness of 100 μm. In the polyenergetic X-ray study, the optimal spectral combination was 40/70 kVp filtered with 100 μm cadmium and 1000 μm copper, respectively. In this case, the minimum detectable microcalcification thickness was 150 μm. The proposed dual energy method provides improved microcalcification detectability in breast imaging with mean glandular dose values within acceptable levels.

Turbulence, selective decay, and merging in the SSX plasma wind tunnel

NASA Astrophysics Data System (ADS)

Gray, Tim; Brown, Michael; Flanagan, Ken; Werth, Alexandra; Lukin, V.

2012-10-01

A helical, relaxed plasma state has been observed in a long cylindrical volume. The cylinder has dimensions L = 1 m and R = 0.08 m. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v >=50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. Typical plasma parameters are Ti= 25 eV, ne>=10^15 cm-3, and B = 0.25 T. The relaxed state is rapidly attained in 1--2 axial Alfv'en times after initiation of the plasma. Magnetic data is favorably compared with an analytical model. Magnetic data exhibits broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement to the minimum energy eigenstate of ∇xB = λB. While the global structure roughly corresponds to the minimum energy eigenstate for the wind tunnel geometry, the plasma is high beta (β= 0.5) and does not have a flat λ profile. Merging of two plasmoids in this configuration results in noticeably more dynamic activity compared to a single plasmoid. These episodes of activity exhibit s

Dual Energy Method for Breast Imaging: A Simulation Study

PubMed Central

2015-01-01

Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in order to overcome the limited kVp range of mammographic units used in previous DE studies, combined with a high resolution CMOS sensor (pixel size of 22.5 μm) for improved resolution. Various filter materials were examined based on their K-absorption edge. Hydroxyapatite (HAp) was used to simulate microcalcifications. The contrast to noise ratio (CNRtc) of the subtracted images was calculated for both monoenergetic and polyenergetic X-ray beams. The optimum monoenergetic pair was 23/58 keV for the low and high energy, respectively, resulting in a minimum detectable microcalcification thickness of 100 μm. In the polyenergetic X-ray study, the optimal spectral combination was 40/70 kVp filtered with 100 μm cadmium and 1000 μm copper, respectively. In this case, the minimum detectable microcalcification thickness was 150 μm. The proposed dual energy method provides improved microcalcification detectability in breast imaging with mean glandular dose values within acceptable levels. PMID:26246848

Ion beam probing of electrostatic fields

NASA Technical Reports Server (NTRS)

Persson, H.

1979-01-01

The determination of a cylindrically symmetric, time-independent electrostatic potential V in a magnetic field B with the same symmetry by measurements of the deflection of a primary beam of ions is analyzed and substantiated by examples. Special attention is given to the requirements on canonical angular momentum and total energy set by an arbitrary, nonmonotone V, to scaling laws obtained by normalization, and to the analogy with ionospheric sounding. The inversion procedure with the Abel analysis of an equivalent problem with a one-dimensional fictitious potential is used in a numerical experiment with application to the NASA Lewis Modified Penning Discharge. The determination of V from a study of secondary beams of ions with increased charge produced by hot plasma electrons is also analyzed, both from a general point of view and with application to the NASA Lewis SUMMA experiment. Simple formulas and geometrical constructions are given for the minimum energy necessary to reach the axis, the whole plasma, and any point in the magnetic field. The common, simplifying assumption that V is a small perturbation is critically and constructively analyzed; an iteration scheme for successively correcting the orbits and points of ionization for the electrostatic potential is suggested.

Assessment of C-Type Darrieus Wind Turbine Under Low Wind Speed Condition

NASA Astrophysics Data System (ADS)

Misaran, M. S.; Rahman, Md. M.; Muzammil, W. K.; Ismail, M. A.

2017-07-01

Harvesting wind energy in in a low wind speed region is deem un-economical if not daunting task. Study shows that a minimum cut in speed of 3.5 m/s is required to extract a meaningful wind energy for electricity while a mean speed of 6 m/s is preferred. However, in Malaysia the mean speed is at 2 m/s with certain potential areas having 3 m/s mean speed. Thus, this work aims to develop a wind turbine that able to operate at lower cut-in speed and produce meaningful power for electricity generation. A C-type Darrieus blade is selected as it shows good potential to operate in arbitrary wind speed condition. The wind turbine is designed and fabricated in UMS labs while the performance of the wind turbine is evaluated in a simulated wind condition. Test result shows that the wind turbine started to rotate at 1 m/s compared to a NACA 0012 Darrieus turbine that started to rotate at 3 m/s. The performance of the turbine shows that it have good potential to be used in an intermittent arbitrary wind speed condition as well as low mean wind speed condition.

Droplet squeezing through a narrow constriction: Minimum impulse and critical velocity

NASA Astrophysics Data System (ADS)

Zhang, Zhifeng; Drapaca, Corina; Chen, Xiaolin; Xu, Jie

2017-07-01

Models of a droplet passing through narrow constrictions have wide applications in science and engineering. In this paper, we report our findings on the minimum impulse (momentum change) of pushing a droplet through a narrow circular constriction. The existence of this minimum impulse is mathematically derived and numerically verified. The minimum impulse happens at a critical velocity when the time-averaged Young-Laplace pressure balances the total minor pressure loss in the constriction. Finally, numerical simulations are conducted to verify these concepts. These results could be relevant to problems of energy optimization and studies of chemical and biomedical systems.

Insights into geometries, stabilities, electronic structures, reactivity descriptors, and magnetic properties of bimetallic Nim Cun-m (m = 1, 2; n = 3-13) clusters: Comparison with pure copper clusters.

PubMed

Singh, Raman K; Iwasa, Takeshi; Taketsugu, Tetsuya

2018-05-25

A long-range corrected density functional theory (LC-DFT) was applied to study the geometric structures, relative stabilities, electronic structures, reactivity descriptors and magnetic properties of the bimetallic NiCu n -1 and Ni 2 Cu n -2 (n = 3-13) clusters, obtained by doping one or two Ni atoms to the lowest energy structures of Cu n , followed by geometry optimizations. The optimized geometries revealed that the lowest energy structures of the NiCu n -1 and Ni 2 Cu n -2 clusters favor the Ni atom(s) situated at the most highly coordinated position of the host copper clusters. The averaged binding energy, the fragmentation energies and the second-order energy differences signified that the Ni doped clusters can continue to gain an energy during the growth process. The electronic structures revealed that the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies of the LC-DFT are reliable and can be used to predict the vertical ionization potential and the vertical electron affinity of the systems. The reactivity descriptors such as the chemical potential, chemical hardness and electrophilic power, and the reactivity principle such as the minimum polarizability principle are operative for characterizing and rationalizing the electronic structures of these clusters. Moreover, doping of Ni atoms into the copper clusters carry most of the total spin magnetic moment. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Ab initio molecular dynamics simulations of AlN responding to low energy particle radiation

NASA Astrophysics Data System (ADS)

Xi, Jianqi; Liu, Bin; Zhang, Yanwen; Weber, William J.

2018-01-01

Ab initio molecular dynamics simulations of low energy recoil events in wurtzite AlN have been performed to determine threshold displacement energies, defect production and evolution mechanisms, role of partial charge transfer during the process, and the influence of irradiation-induced defects on the properties of AlN. The results show that the threshold displacement energies, Ed, along the direction parallel to the basal planes are smaller than those perpendicular to the basal planes. The minimum Ed values are determined to be 19 eV and 55 eV for N and Al atom, respectively, which occur along the [ 1 ¯ 1 ¯ 20 ] direction. In general, the threshold displacement energies for N are smaller than those for Al atom, indicating the N defects would be dominant under irradiation. The defect production mechanisms have been analyzed. It is found that charge transfer and redistribution for both the primary knock-on atom and the subsequent recoil atoms play a significant role in defect production and evolution. Similar to the trend in oxide materials, there is a nearly linear relationship between Ed and the total amount of charge transfer at the potential energy peak in AlN, which provides guidance on the development of charge-transfer interatomic potentials for classic molecular dynamics simulations. Finally, the response behavior of AlN to low energy irradiation is qualitatively investigated. The existence of irradiation-induced defects significantly modifies the electronic structure, and thus affects the magnetic, electronic and optical properties of AlN. These findings further enrich the understanding of defects in the wide bandgap semiconductor of AlN.

7 CFR 2902.39 - Floor strippers.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 15 2011-01-01 2011-01-01 false Floor strippers. 2902.39 Section 2902.39 Agriculture Regulations of the Department of Agriculture (Continued) OFFICE OF ENERGY POLICY AND NEW USES, DEPARTMENT OF... mechanical assistance. (b) Minimum biobased content. The preferred procurement product must have a minimum...

40 CFR 600.010 - Vehicle test requirements and minimum data requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Vehicle test requirements and minimum data requirements. 600.010 Section 600.010 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES General...

40 CFR 600.010 - Vehicle test requirements and minimum data requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Vehicle test requirements and minimum data requirements. 600.010 Section 600.010 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES General...

40 CFR 600.010 - Vehicle test requirements and minimum data requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Vehicle test requirements and minimum data requirements. 600.010 Section 600.010 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF MOTOR VEHICLES General...

Phenolic acids potentiate colistin-mediated killing of Acinetobacter baumannii by inducing redox imbalance.

PubMed

Ajiboye, Taofeek O; Skiebe, Evelyn; Wilharm, Gottfried

2018-05-01

Phenolic acids with catechol groups are good prooxidants because of their low redox potential. In this study, we provided data showing that phenolic acids, caffeic acid, gallic acid and protocatechuic acid, enhanced colistin-mediated bacterial death by inducing redox imbalance. The minimum inhibitory concentrations of these phenolic acids against Acinetobacter baumannii AB5075 were considerably lowered for ΔsodB and ΔkatG mutants. Checkerboard assay shows synergistic interactions between colistin and phenolic acids. The phenolic acids exacerbated colistin-induced oxidative stress in A. baumannii AB5075 through increased superoxide anion generation, NAD + /NADH and ADP/ATP ratio. In parallel, the level of reduced glutathione was significantly lowered. We conclude that phenolic acids potentiate colistin-induced oxidative stress in A. baumannii AB5075 by increasing ROS generation, energy metabolism and electron transport chain activity with a concomitant decrease in glutathione. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Observation of a Relaxed Plasma State in a Quasi-Infinite Cylinder

NASA Astrophysics Data System (ADS)

Gray, T.; Brown, M. R.; Dandurand, D.

2013-02-01

A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v≥50km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1-2 axial Alfvén times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement with the minimum energy eigenstate of ∇×B=λB.

Observation of a relaxed plasma state in a quasi-infinite cylinder.

PubMed

Gray, T; Brown, M R; Dandurand, D

2013-02-22

A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v ≥ 50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1-2 axial Alfvén times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement with the minimum energy eigenstate of [Symbol: see text] × B = λB.

Potential of Micro Hydroelectric Generator Embedded at 30,000 PE Effluent Discharge of Sewerage Treatment Plant

NASA Astrophysics Data System (ADS)

Che Munaaim, M. A.; Razali, N.; Ayob, A.; Hamidin, N.; Othuman Mydin, M. A.

2018-03-01

A micro hydroelectric generator is an energy conversion approach to generate electricity from potential (motion) energy to an electrical energy. In this research, it is desired to be implemented by using a micro hydroelectric generator which is desired to be embedded at the continuous flow of effluent discharge point of domestic sewerage treatment plant (STP). This research evaluates the potential of electricity generation from micro hydroelectric generator attached to 30,000 PE sewerage treatment plant. The power output obtained from calculation of electrical power conversion is used to identify the possibility of this system and its ability to provide electrical energy, which can minimize the cost of electric bill especially for the pumping system. The overview of this system on the practical application with the consideration of payback period is summarized. The ultimate aim of the whole application is to have a self-ecosystem electrical power generated for the internal use of STP by using its own flowing water in supporting the sustainable engineering towards renewable energy and energy efficient approach. The results shows that the output power obtained is lower than expected output power (12 kW) and fall beyond of the range of a micro hydro power (5kW - 100kW) since it is only generating 1.58 kW energy by calculation. It is also observed that the estimated payback period is longer which i.e 7 years to recoup the return of investment. A range of head from 4.5 m and above for the case where the flow shall at least have maintained at 0.05 m3/s in the selected plant in order to achieved a feasible power output. In conclusion, wastewater treatment process involves the flowing water (potential energy) especially at the effluent discharge point of STP is possibly harvested for electricity generation by embedding the micro hydroelectric generator. However, the selection of STP needs to have minimum 4.5 meter head with 0.05 m3/s of continuously flowing water to make it feasible to harvest.

Free-end adaptive nudged elastic band method for locating transition states in minimum energy path calculation.

PubMed

Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

2016-09-07

A free-end adaptive nudged elastic band (FEA-NEB) method is presented for finding transition states on minimum energy paths, where the energy barrier is very narrow compared to the whole paths. The previously proposed free-end nudged elastic band method may suffer from convergence problems because of the kinks arising on the elastic band if the initial elastic band is far from the minimum energy path and weak springs are adopted. We analyze the origin of the formation of kinks and present an improved free-end algorithm to avoid the convergence problem. Moreover, by coupling the improved free-end algorithm and an adaptive strategy, we develop a FEA-NEB method to accurately locate the transition state with the elastic band cut off repeatedly and the density of images near the transition state increased. Several representative numerical examples, including the dislocation nucleation in a penta-twinned nanowire, the twin boundary migration under a shear stress, and the cross-slip of screw dislocation in face-centered cubic metals, are investigated by using the FEA-NEB method. Numerical results demonstrate both the stability and efficiency of the proposed method.

Electron affinity and surface states of GaN m -plane facets: Implication for electronic self-passivation

NASA Astrophysics Data System (ADS)

Portz, V.; Schnedler, M.; Eisele, H.; Dunin-Borkowski, R. E.; Ebert, Ph.

2018-03-01

The electron affinity and surface states are of utmost importance for designing the potential landscape within (heterojunction) nanowires and hence for tuning conductivity and carrier lifetimes. Therefore, we determined for stoichiometric nonpolar GaN (10 1 ¯0 ) m -plane facets, i.e., the dominating sidewalls of GaN nanowires, the electron affinity to 4.06 ±0.07 eV and the energy of the empty Ga-derived surface state in the band gap to 0.99 ±0.08 eV below the conduction band minimum using scanning tunneling spectroscopy. These values imply that the potential landscape within GaN nanowires is defined by a surface state-induced Fermi-level pinning, creating an upward band bending at the sidewall facets, which provides an electronic passivation.

Strong localization induced anomalous temperature dependence exciton emission above 300 K from SnO{sub 2} quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, S. S., E-mail: sspan@issp.ac.cn, E-mail: ghli@issp.ac.cn; Li, F. D.; Liu, Q. W.

2015-05-07

SnO{sub 2} quantum dots (QDs) are potential materials for deep ultraviolet (DUV) light emitting devices. In this study, we report the temperature and excitation power-dependent exciton luminescence from SnO{sub 2} QDs. The exciton emission exhibits anomalous blue shift, accompanied with band width reduction with increasing temperature and excitation power above 300 K. The anomalous temperature dependences of the peak energy and band width are well interpreted by the strongly localized carrier thermal hopping process and Gaussian shape of band tails states, respectively. The localized wells and band tails at conduction minimum are considered to be induced by the surface oxygen defectsmore » and local potential fluctuation in SnO{sub 2} QDs.« less

Parametric study of minimum converter loss in an energy-storage dc-to-dc converter

NASA Technical Reports Server (NTRS)

Wong, R. C.; Owen, H. A., Jr.; Wilson, T. G.

1982-01-01

Through a combination of analytical and numerical minimization procedures, a converter design that results in the minimum total converter loss (including core loss, winding loss, capacitor and energy-storage-reactor loss, and various losses in the semiconductor switches) is obtained. Because the initial phase involves analytical minimization, the computation time required by the subsequent phase of numerical minimization is considerably reduced in this combination approach. The effects of various loss parameters on the optimum values of the design variables are also examined.

Roton Minimum as a Fingerprint of Magnon-Higgs Scattering in Ordered Quantum Antiferromagnets.

PubMed

Powalski, M; Uhrig, G S; Schmidt, K P

2015-11-13

A quantitative description of magnons in long-range ordered quantum antiferromagnets is presented which is consistent from low to high energies. It is illustrated for the generic S=1/2 Heisenberg model on the square lattice. The approach is based on a continuous similarity transformation in momentum space using the scaling dimension as the truncation criterion. Evidence is found for significant magnon-magnon attraction inducing a Higgs resonance. The high-energy roton minimum in the magnon dispersion appears to be induced by strong magnon-Higgs scattering.

Simulation of the outdoor energy efficiency of an autonomous solar kit based on meteorological data for a site in Central Europa

NASA Astrophysics Data System (ADS)

Bouzaki, Mohammed Moustafa; Chadel, Meriem; Benyoucef, Boumediene; Petit, Pierre; Aillerie, Michel

2016-07-01

This contribution analyzes the energy provided by a solar kit dedicated to autonomous usage and installed in Central Europa (Longitude 6.10°; Latitude 49.21° and Altitude 160 m) by using the simulation software PVSYST. We focused the analysis on the effect of temperature and solar irradiation on the I-V characteristic of a commercial PV panel. We also consider in this study the influence of charging and discharging the battery on the generator efficiency. Meteorological data are integrated into the simulation software. As expected, the solar kit provides an energy varying all along the year with a minimum in December. In the proposed approach, we consider this minimum as the lowest acceptable energy level to satisfy the use. Thus for the other months, a lost in the available renewable energy exists if no storage system is associated.

Dynamic Mechanism of a Fluorinated Oxime Reactivator Unbinding from AChE Gorge in Polarizable Water.

PubMed

Pathak, Arup K; Bandyopadhyay, Tusar

2018-04-12

A well-tempered metadynamics simulation is performed to study the unbinding process of a fluorinated oxime (FHI-6) drug from the active-site gorge of acetylcholinesterase enzyme in a polarizable water medium. Cation-π interactions and water bridge and hydrogen bridge formations between the protein and the drug molecule are found to strongly influence the unbinding process, forming basins and barriers along the gorge pathway. Distinct unbinding pathways are found when FHI-6 was compared with its recently reported nonfluorinated analogue, HI-6. For example, because of permanent positive charges on both the pyridinium rings of HI-6, it exhibits the minimum in the potential of mean force of the unbinding process in the gorge mouth (where the peripheral anion site, PAS, of the enzyme is located), which is largely caused by cation-π interactions. However, the same interaction, both in the catalytic active-site (CAS) and PAS regions, is found to be greatly enhanced in its lipophilic fluorinated analogue, FHI-6, causing a deep potential energy minimum in the bound state. This may render FHI-6 to be held more firmly in the CAS region of the gorge, as is also evidenced from the microkinetics of unbinding transitions, measured through a combination of metadynamics and hyperdynamics simulations.

Metabolic versatility of a novel N2 -fixing Alphaproteobacterium isolated from a marine oxygen minimum zone.

PubMed

Martínez-Pérez, Clara; Mohr, Wiebke; Schwedt, Anne; Dürschlag, Julia; Callbeck, Cameron M; Schunck, Harald; Dekaezemacker, Julien; Buckner, Caroline R T; Lavik, Gaute; Fuchs, Bernhard M; Kuypers, Marcel M M

2018-02-01

The N 2 -fixing (diazotrophic) community in marine ecosystems is dominated by non-cyanobacterial microorganisms. Yet, very little is known about their identity, function and ecological relevance due to a lack of cultured representatives. Here we report a novel heterotrophic diazotroph isolated from the oxygen minimum zone (OMZ) off Peru. The new species belongs to the genus Sagittula (Rhodobacteraceae, Alphaproteobacteria) and its capability to fix N 2 was confirmed in laboratory experiments. Genome sequencing revealed that it is a strict heterotroph with a high versatility in substrate utilization and energy acquisition mechanisms. Pathways for sulfide oxidation and nitrite reduction to nitrous oxide are encoded in the genome and might explain the presence throughout the Peruvian OMZ. The genome further indicates that this novel organism could be in direct interaction with other microbes or particles. NanoSIMS analyses were used to compare the metabolic potential of S. castanea with single-cell activity in situ; however, N 2 fixation by this diazotroph could not be detected at the isolation site. While the biogeochemical impact of S. castanea is yet to be resolved, its abundance and widespread distribution suggests that its potential to contribute to the marine N input could be significant at a larger geographical scale. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Hydrogen Sulfide as a Scavenger of Sulfur Atomic Cation.

PubMed

Fortenberry, Ryan C; Trabelsi, Tarek; Francisco, Joseph S

2018-06-07

The well-studied hydrogen sulfide molecule is shown here for the first time to form a S-S bond barrierlessly with sulfur atomic cation to produce stable H 2 SS + , a compound for which there is nearly no literature data. Previous work has shown that the reaction of hydrogen sulfide with neutral atomic sulfur will likely only take place at high pressures. Conversely, this work shows that hydrogen sulfide will readily bind with atomic sulfur cation first through the 1 4 A″ state from association of H 2 S with S + ( 4 S) and then will relax to the nearly degenerate 1 2 A' or 1 2 A″ states. S + ( 4 S) + H 2 S lies 29.5 kcal/mol above the 1 4 A″ H 2 SS + minimum. The 1 4 A″ H 2 SS + minimum in the S-S bond is also directly intersected by the doublet potential energy surface. As the S-S bond shortens in the association, the 1 2 A' and 1 2 A″ states split, falling 33.5 and 26.4 kcal/mol, respectively, below the 1 4 A″ state. Hence, this work is opening the door for novel synthesis of S-S bonds or potential removal of the common H 2 S toxin/pollutant through concatenation and subsequent precipitation.

Dynamical approach to the cosmological constant.

PubMed

Mukohyama, Shinji; Randall, Lisa

2004-05-28

We consider a dynamical approach to the cosmological constant. There is a scalar field with a potential whose minimum occurs at a generic, but negative, value for the vacuum energy, and it has a nonstandard kinetic term whose coefficient diverges at zero curvature as well as the standard kinetic term. Because of the divergent coefficient of the kinetic term, the lowest energy state is never achieved. Instead, the cosmological constant automatically stalls at or near zero. The merit of this model is that it is stable under radiative corrections and leads to stable dynamics, despite the singular kinetic term. The model is not complete, however, in that some reheating is required. Nonetheless, our approach can at the very least reduce fine-tuning by 60 orders of magnitude or provide a new mechanism for sampling possible cosmological constants and implementing the anthropic principle.