Absorbing-state phase transitions with extremal dynamics
NASA Astrophysics Data System (ADS)
Dickman, Ronald; Garcia, Guilherme J. M.
2005-06-01
Extremal dynamics represents a path to self-organized criticality in which the order parameter is tuned to a value of zero. The order parameter is associated with a phase transition to an absorbing state. Given a process that exhibits a phase transition to an absorbing state, we define an “extremal absorbing” process, providing the link to the associated extremal (nonabsorbing) process. Stationary properties of the latter correspond to those at the absorbing-state phase transition in the former. Studying the absorbing version of an extremal dynamics model allows to determine certain critical exponents that are not otherwise accessible. In the case of the Bak-Sneppen (BS) model, the absorbing version is closely related to the “ f -avalanche” introduced by Paczuski, Maslov, and Bak [Phys. Rev. E 53, 414 (1996)], or, in spreading simulations to the “BS branching process” also studied by these authors. The corresponding nonextremal process belongs to the directed percolation universality class. We revisit the absorbing BS model, obtaining refined estimates for the threshold and critical exponents in one dimension. We also study an extremal version of the usual contact process, using mean-field theory and simulation. The extremal condition slows the spread of activity and modifies the critical behavior radically, defining an “extremal directed percolation” universality class of absorbing-state phase transitions. Asymmetric updating is a relevant perturbation for this class, even though it is irrelevant for the corresponding nonextremal class.
Absorbing State Phase Transition with Competing Quantum and Classical Fluctuations.
Marcuzzi, Matteo; Buchhold, Michael; Diehl, Sebastian; Lesanovsky, Igor
2016-06-17
Stochastic processes with absorbing states feature examples of nonequilibrium universal phenomena. While the classical regime has been thoroughly investigated in the past, relatively little is known about the behavior of these nonequilibrium systems in the presence of quantum fluctuations. Here, we theoretically address such a scenario in an open quantum spin model which, in its classical limit, undergoes a directed percolation phase transition. By mapping the problem to a nonequilibrium field theory, we show that the introduction of quantum fluctuations stemming from coherent, rather than statistical, spin flips alters the nature of the transition such that it becomes first order. In the intermediate regime, where classical and quantum dynamics compete on equal terms, we highlight the presence of a bicritical point with universal features different from the directed percolation class in a low dimension. We finally propose how this physics could be explored within gases of interacting atoms excited to Rydberg states. PMID:27367395
Absorbing State Phase Transition with Competing Quantum and Classical Fluctuations
NASA Astrophysics Data System (ADS)
Marcuzzi, Matteo; Buchhold, Michael; Diehl, Sebastian; Lesanovsky, Igor
2016-06-01
Stochastic processes with absorbing states feature examples of nonequilibrium universal phenomena. While the classical regime has been thoroughly investigated in the past, relatively little is known about the behavior of these nonequilibrium systems in the presence of quantum fluctuations. Here, we theoretically address such a scenario in an open quantum spin model which, in its classical limit, undergoes a directed percolation phase transition. By mapping the problem to a nonequilibrium field theory, we show that the introduction of quantum fluctuations stemming from coherent, rather than statistical, spin flips alters the nature of the transition such that it becomes first order. In the intermediate regime, where classical and quantum dynamics compete on equal terms, we highlight the presence of a bicritical point with universal features different from the directed percolation class in a low dimension. We finally propose how this physics could be explored within gases of interacting atoms excited to Rydberg states.
Absorbing-state phase transitions on percolating lattices.
Lee, Man Young; Vojta, Thomas
2009-04-01
We study nonequilibrium phase transitions of reaction-diffusion systems defined on randomly diluted lattices, focusing on the transition across the lattice percolation threshold. To develop a theory for this transition, we combine classical percolation theory with the properties of the supercritical nonequilibrium system on a finite-size cluster. In the case of the contact process, the interplay between geometric criticality due to percolation and dynamical fluctuations of the nonequilibrium system leads to a different universality class. The critical point is characterized by ultraslow activated dynamical scaling and accompanied by strong Griffiths singularities. To confirm the universality of this exotic scaling scenario we also study the generalized contact process with several (symmetric) absorbing states and we support our theory by extensive Monte Carlo simulations. PMID:19518178
Hybrid phase transition into an absorbing state: Percolation and avalanches.
Lee, Deokjae; Choi, S; Stippinger, M; Kertész, J; Kahng, B
2016-04-01
Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent β_{m} of the order parameter is 1/2 under general conditions, while the value of the exponent γ_{m} characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, β_{a} and γ_{a}. These two critical behaviors are coupled by a scaling law: 1-β_{m}=γ_{a}. PMID:27176256
Hybrid phase transition into an absorbing state: Percolation and avalanches
NASA Astrophysics Data System (ADS)
Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.
2016-04-01
Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .
de Oliveira, M M; da Luz, M G E; Fiore, C E
2015-12-01
Based on quasistationary distribution ideas, a general finite size scaling theory is proposed for discontinuous nonequilibrium phase transitions into absorbing states. Analogously to the equilibrium case, we show that quantities such as response functions, cumulants, and equal area probability distributions all scale with the volume, thus allowing proper estimates for the thermodynamic limit. To illustrate these results, five very distinct lattice models displaying nonequilibrium transitions-to single and infinitely many absorbing states-are investigated. The innate difficulties in analyzing absorbing phase transitions are circumvented through quasistationary simulation methods. Our findings (allied to numerical studies in the literature) strongly point to a unifying discontinuous phase transition scaling behavior for equilibrium and this important class of nonequilibrium systems. PMID:26764651
Phase transitions of the generalized contact process with two absorbing states.
Lee, Man Young; Vojta, Thomas
2010-06-01
We investigate the generalized contact process with two absorbing states in one space dimension by means of large-scale Monte Carlo simulations. Treating the creation rate of active sites between inactive domains as an independent parameter leads to a rich phase diagram. In addition to the conventional active and inactive phases we find a parameter region where the simple contact process is inactive, but an infinitesimal creation rate at the boundary between inactive domains is sufficient to take the system into the active phase. Thus, the generalized contact process has two different phase transition lines. The point separating them shares some characteristics with a multicritical point. We also study in detail the critical behaviors of these transitions and their universality. PMID:20866399
Lee, Sang Bub
2014-06-01
The critical behavior of absorbing phase transitions for two typical models in the Manna universality class, the conserved Manna model and the conserved lattice gas model, both on a square lattice, was investigated using the natural initial states. Various critical exponents were estimated using the static and dynamic simulations. The exponents characterizing dynamics of active particles differ considerably from the known exponents obtained using the random initial states, whereas those associated with the steady-state quantities remain the same. The critical exponents for both models were consistent with errors of less than 1% and satisfied the known scaling relations; thus, the known violation of scaling relations for models with a conserved field was resolved using the natural initial states. The results differed by 7%∼12% from the directed percolation values. PMID:25019750
Continuous and discontinuous absorbing-state phase transitions on Voronoi-Delaunay random lattices.
de Oliveira, Marcelo M; Alves, Sidiney G; Ferreira, Silvio C
2016-01-01
We study absorbing-state phase transitions (APTs) in two-dimensional Voronoi-Delaunay (VD) random lattices with quenched coordination disorder. Quenched randomness usually changes the criticality and destroys discontinuous transitions in low-dimensional nonequilibrium systems. We performed extensive simulations of the Ziff-Gulari-Barshad model, and verified that the VD disorder does not change the nature of its discontinuous transition. Our results corroborate recent findings of Barghathi and Vojta [H. Barghathi and T. Vojta, Phys. Rev. Lett. 113, 120602 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.120602], stating the irrelevance of topological disorder in a class of random lattices that includes VD, and raise the interesting possibility that disorder in nonequilibrium APT may, under certain conditions, be irrelevant for the phase coexistence. We also verify that the VD disorder is irrelevant for the critical behavior of models belonging to the directed percolation and Manna universality classes. PMID:26871027
Continuous and discontinuous absorbing-state phase transitions on Voronoi-Delaunay random lattices
NASA Astrophysics Data System (ADS)
de Oliveira, Marcelo M.; Alves, Sidiney G.; Ferreira, Silvio C.
2016-01-01
We study absorbing-state phase transitions (APTs) in two-dimensional Voronoi-Delaunay (VD) random lattices with quenched coordination disorder. Quenched randomness usually changes the criticality and destroys discontinuous transitions in low-dimensional nonequilibrium systems. We performed extensive simulations of the Ziff-Gulari-Barshad model, and verified that the VD disorder does not change the nature of its discontinuous transition. Our results corroborate recent findings of Barghathi and Vojta [H. Barghathi and T. Vojta, Phys. Rev. Lett. 113, 120602 (2014), 10.1103/PhysRevLett.113.120602], stating the irrelevance of topological disorder in a class of random lattices that includes VD, and raise the interesting possibility that disorder in nonequilibrium APT may, under certain conditions, be irrelevant for the phase coexistence. We also verify that the VD disorder is irrelevant for the critical behavior of models belonging to the directed percolation and Manna universality classes.
Absorbing phase transition in a four-state predator-prey model in one dimension
NASA Astrophysics Data System (ADS)
Chatterjee, Rakesh; Mohanty, P. K.; Basu, Abhik
2011-05-01
The model of competition between densities of two different species, called predator and prey, is studied on a one-dimensional periodic lattice, where each site can be in one of the four states, say, empty, or occupied by a single predator, or occupied by a single prey, or by both. Along with the pairwise death of predators and growth of prey, we introduce an interaction where the predators can eat one of the neighboring prey and reproduce a new predator there instantly. The model shows a non-equilibrium phase transition into an unusual absorbing state where predators are absent and the lattice is fully occupied by prey. The critical exponents of the system are found to be different from those of the directed percolation universality class and they are robust against addition of explicit diffusion.
Active-to-absorbing-state phase transition in an evolving population with mutation
NASA Astrophysics Data System (ADS)
Sarkar, Niladri
2015-10-01
We study the active to absorbing phase transition (AAPT) in a simple two-component model system for a species and its mutant. We uncover the nontrivial critical scaling behavior and weak dynamic scaling near the AAPT that shows the significance of mutation and highlights the connection of this model with the well-known directed percolation universality class. Our model should be a useful starting point to study how mutation may affect extinction or survival of a species.
Active-to-absorbing-state phase transition in an evolving population with mutation.
Sarkar, Niladri
2015-10-01
We study the active to absorbing phase transition (AAPT) in a simple two-component model system for a species and its mutant. We uncover the nontrivial critical scaling behavior and weak dynamic scaling near the AAPT that shows the significance of mutation and highlights the connection of this model with the well-known directed percolation universality class. Our model should be a useful starting point to study how mutation may affect extinction or survival of a species. PMID:26565171
Diffusion, Absorbing States, and Nonequilibrium Phase Transitions in Range Expansions and Evolution
NASA Astrophysics Data System (ADS)
Lavrentovich, Maxim Olegovich
The spatial organization of a population plays a key role in its evolutionary dynamics and growth. In this thesis, we study the dynamics of range expansions, in which populations expand into new territory. Focussing on microbes, we first consider how nutrients diffuse and are absorbed in a population, allowing it to grow. These nutrients may be absorbed before reaching the population interior, and this "nutrient shielding'' can confine the growth to a thin region on the population periphery. A thin population front implies a small local effective population size and enhanced number fluctuations (or genetic drift). We then study evolutionary dynamics under these growth conditions. In particular, we calculate the survival probability of mutations with a selective advantage occurring at the population front for two-dimensional expansions (e.g., along the surface of an agar plate), and three-dimensional expansions (e.g., an avascular tumor). We also consider the effects of irreversible, deleterious mutations which can lead to the loss of the advantageous mutation in the population via a "mutational meltdown,'' or non-equilibrium phase transition. We examine the effects of an inflating population frontier on the phase transition. Finally, we discuss how spatial dimension and frontier roughness influence range expansions of mutualistic, cross-feeding variants. We find here universal features of the phase diagram describing the onset of a mutualistic phase in which the variants remain mixed at long times.
Fiore, Carlos E
2014-02-01
Motivated by recent findings, we discuss the existence of a direct and robust mechanism providing discontinuous absorbing transitions in short-range systems with single species, with no extra symmetries or conservation laws. We consider variants of the contact process, in which at least two adjacent particles (instead of one, as commonly assumed) are required to create a new species. Many interaction rules are analyzed, including distinct cluster annihilations and a modified version of the original pair contact process. Through detailed time-dependent numerical simulations, we find that for our modified models, the phase transitions are of first order, hence contrasting with their corresponding usual formulations in the literature, which are of second order. By calculating the order-parameter distributions, the obtained bimodal shapes as well as the finite-scale analysis reinforce coexisting phases and thus a discontinuous transition. These findings strongly suggest that the above particle creation requirements constitute a minimum and fundamental mechanism determining the phase coexistence in short-range contact processes. PMID:25353419
Sarkar, Niladri; Basu, Abhik
2012-08-01
We investigate the scaling properties of phase transitions between survival and extinction (active-to-absorbing-state phase transition, AAPT) in a model that by itself belongs to the directed percolation (DP) universality class, interacting with a spatiotemporally fluctuating environment having its own nontrivial dynamics. We model the environment by (i) a randomly stirred fluid, governed by the Navier-Stokes (NS) equation, and (ii) a fluctuating surface, described either by the Kardar-Parisi-Zhang (KPZ) or the Edward-Wilkinson (EW) equations. We show, by using a one-loop perturbative field theoretic setup that, depending upon the spatial scaling of the variance of the external forces that drive the environment (i.e., the NS, KPZ, or EW equations), the system may show weak or strong dynamic scaling at the critical point of active-to-absorbing-state phase transitions. In the former case AAPT displays scaling belonging to the DP universality class, whereas in the latter case the universal behavior is different. PMID:23005737
Hyperuniformity of critical absorbing states.
Hexner, Daniel; Levine, Dov
2015-03-20
The properties of the absorbing states of nonequilibrium models belonging to the conserved directed percolation universality class are studied. We find that, at the critical point, the absorbing states are hyperuniform, exhibiting anomalously small density fluctuations. The exponent characterizing the fluctuations is measured numerically, a scaling relation to other known exponents is suggested, and a new correlation length relating to this ordering is proposed. These results may have relevance to photonic band-gap materials. PMID:25839254
Hyperuniformity of Critical Absorbing States
NASA Astrophysics Data System (ADS)
Hexner, Daniel; Levine, Dov
2015-03-01
The properties of the absorbing states of nonequilibrium models belonging to the conserved directed percolation universality class are studied. We find that, at the critical point, the absorbing states are hyperuniform, exhibiting anomalously small density fluctuations. The exponent characterizing the fluctuations is measured numerically, a scaling relation to other known exponents is suggested, and a new correlation length relating to this ordering is proposed. These results may have relevance to photonic band-gap materials.
Cusps, self-organization, and absorbing states.
Bonachela, Juan A; Alava, Mikko; Muñoz, Miguel A
2009-05-01
Elastic interfaces embedded in (quenched) random media exhibit metastability and stick-slip dynamics. These nontrivial dynamical features have been shown to be associated with cusp singularities of the coarse-grained disorder correlator. Here we show that annealed systems with many absorbing states and a conservation law but no quenched disorder exhibit identical cusps. On the other hand, similar nonconserved systems in the directed percolation class are also shown to exhibit cusps but of a different type. These results are obtained both by a recent method to explicitly measure disorder correlators and by defining an alternative new protocol inspired by self-organized criticality, which opens the door to easily accessible experimental realizations. PMID:19518401
Generalized contact process with two symmetric absorbing states in two dimensions.
Lee, Man Young; Vojta, Thomas
2011-01-01
We explore the two-dimensional generalized contact process with two absorbing states by means of large-scale Monte-Carlo simulations. In part of the phase diagram, an infinitesimal creation rate of active sites between inactive domains is sufficient to take the system from the inactive phase to the active phase. The system, therefore, displays two different nonequilibrium phase transitions. The critical behavior of the generic transition is compatible with the generalized voter universality class, implying that the symmetry-breaking and absorbing transitions coincide. In contrast, the transition at zero domain-boundary activation rate is not critical. PMID:21405668
System size expansion for systems with an absorbing state.
Di Patti, Francesca; Azaele, Sandro; Banavar, Jayanth R; Maritan, Amos
2011-01-01
The well-known van Kampen system size expansion, while of rather general applicability, is shown to fail to reproduce some qualitative features of the time evolution for systems with an absorbing state, apart from a transient initial time interval. We generalize the van Kampen ansatz by introducing a new prescription leading to non-Gaussian fluctuations around the absorbing state. The two expansion predictions are explicitly compared for the infinite range voter model with speciation as a paradigmatic model with an absorbing state. The new expansion, both for a finite size system in the large time limit and at finite time in the large size limit, converges to the exact solution as obtained in a numerical implementation using the Gillespie algorithm. Furthermore, the predicted lifetime distribution is shown to have the correct asymptotic behavior. PMID:21405654
Dynamics of a first-order transition to an absorbing state.
Néel, Baptiste; Rondini, Ignacio; Turzillo, Alex; Mujica, Nicolás; Soto, Rodrigo
2014-04-01
A granular system confined in a quasi-two-dimensional box that is vertically vibrated can transit to an absorbing state in which all particles bounce vertically in phase with the box, with no horizontal motion. In principle, this state can be reached for any density lower than the one corresponding to one complete monolayer, which is then the critical density. Below this critical value, the transition to the absorbing state is of first order, with long metastable periods, followed by rapid transitions driven by homogeneous nucleation. Molecular dynamics simulations and experiments show that there is a dramatic increase on the metastable times far below the critical density; in practice, it is impossible to observe spontaneous transitions close to the critical density. This peculiar feature is a consequence of the nonequilibrium nature of this first-order transition to the absorbing state. A Ginzburg-Landau model, with multiplicative noise, describes qualitatively the observed phenomena and explains the macroscopic size of the critical nuclei. The nuclei become of small size only close to a second critical point where the active phase becomes unstable via a saddle node bifurcation. It is only close to this second critical point that experiments and simulations can evidence spontaneous transitions to the absorbing state while the metastable times grow dramatically moving away from it. PMID:24827240
Noise-induced absorbing phase transition in a model of opinion formation
NASA Astrophysics Data System (ADS)
Vieira, Allan R.; Crokidakis, Nuno
2016-08-01
In this work we study a 3-state (+1, -1, 0) opinion model in the presence of noise and disorder. We consider pairwise competitive interactions, with a fraction p of those interactions being negative (disorder). Moreover, there is a noise q that represents the probability of an individual spontaneously change his opinion to the neutral state. Our aim is to study how the increase/decrease of the fraction of neutral agents affects the critical behavior of the system and the evolution of opinions. We derive analytical expressions for the order parameter of the model, as well as for the stationary fraction of each opinion, and we show that there are distinct phase transitions. One is the usual ferro-paramagnetic transition, that is in the Ising universality class. In addition, there are para-absorbing and ferro-absorbing transitions, presenting the directed percolation universality class. Our results are complemented by numerical simulations.
Hysteresis of transient populations in absorbing-state systems
NASA Astrophysics Data System (ADS)
Kapitanchuk, Oleksiy L.; Marchenko, Oleksij M.; Teslenko, Victor I.
2016-06-01
A nonequilibrium density matrix theory is used in order to explicitly describe the hysteresis interrelation between populations of nonstationary states in an absorbing multi-stage chain system in the one-particle approximation. As an illustrative example, we restrict ourselves to consideration of the 3-stage absorbing case for which we identify three types of the hysteresis; that is, the causal time dependent hysteresis with leaf-like and triangle-like closed loops, the hidden hysteresis with broken-line loops and the true hysteresis with open loops. Furthermore, we observe a common critical threshold for the hysteresis types and ascertain a reciprocal correspondence of this threshold as between the types as well with the experiment.
The analysis of a state-switched absorber design concept
NASA Astrophysics Data System (ADS)
Albanese, Anne-Marie; Cunefare, Kenneth
2002-11-01
A tuned vibration absorber (TVA) is a spring-damper-mass system used in many industries for the suppression of a specific vibration frequency, and has application for the suppression of aircraft fuselage vibration. A state-switched absorber (SSA) is similar to a TVA, except that one or more components in the SSA is able to instantaneously and discretely change properties, thus increasing the effective bandwidth of vibration suppression. In order to design a replacement SSA for the classic TVA, the SSA must operate in the appropriate frequency range, be lightweight, and compact. An optimal SSA will also have a maximal frequency range between which it can switch. This paper discusses the development of a magnetorheological (MR) silicone gel used as the SSA switching element, the shape required to maintain a magnetic flux path, and the contribution of the magnet-mass to frequency shifting. The MR gel is iron-doped silicone, cured in the presence of a magnetic field. During operation, the applied magnetic flux is modified to change the natural frequency. The applied flux requirement forces the SSA to be a small ring. The SSA is designed to operate below 100 Hz.
Random field disorder at an absorbing state transition in one and two dimensions
NASA Astrophysics Data System (ADS)
Barghathi, Hatem; Vojta, Thomas
2016-02-01
We investigate the behavior of nonequilibrium phase transitions under the influence of disorder that locally breaks the symmetry between two symmetrical macroscopic absorbing states. In equilibrium systems such "random-field" disorder destroys the phase transition in low dimensions by preventing spontaneous symmetry breaking. In contrast, we show here that random-field disorder fails to destroy the nonequilibrium phase transition of the one- and two-dimensional generalized contact process. Instead, it modifies the dynamics in the symmetry-broken phase. Specifically, the dynamics in the one-dimensional case is described by a Sinai walk of the domain walls between two different absorbing states. In the two-dimensional case, we map the dynamics onto that of the well studied low-temperature random-field Ising model. We also study the critical behavior of the nonequilibrium phase transition and characterize its universality class in one dimension. We support our results by large-scale Monte Carlo simulations, and we discuss the applicability of our theory to other systems.
CO2 Capture with Liquid-to-Solid Absorbents: CO2 Capture Process Using Phase-Changing Absorbents
2010-10-01
IMPACCT Project: GE and the University of Pittsburgh are developing a unique CO2 capture process in which a liquid absorbent, upon contact with CO2, changes into a solid phase. Once in solid form, the material can be separated and the CO2 can be released for storage by heating. Upon heating, the absorbent returns to its liquid form, where it can be reused to capture more CO2. The approach is more efficient than other solventbased processes because it avoids the heating of extraneous solvents such as water. This ultimately leads to a lower cost of CO2 capture and will lower the additional cost to produce electricity for coal-fired power plants that retrofit their facilities to include this technology.
Cao, Tun; Wei, Chen-wei; Simpson, Robert E; Zhang, Lei; Cryan, Martin J
2014-01-01
We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm(2), owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage. PMID:24492415
Cao, Tun; Wei, Chen-wei; Simpson, Robert E.; Zhang, Lei; Cryan, Martin J.
2014-01-01
We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm2, owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage. PMID:24492415
The Two-Phase, Two-Velocity Ionized Absorber in the Seyfert 1 Galaxy NGC 5548
NASA Astrophysics Data System (ADS)
Andrade-Velázquez, Mercedes; Krongold, Yair; Elvis, Martin; Nicastro, Fabrizio; Brickhouse, Nancy; Binette, Luc; Mathur, Smita; Jiménez-Bailón, Elena
2010-03-01
We present an analysis of X-ray high-quality grating spectra of the Seyfert 1 galaxy NGC 5548 using archival Chandra-High Energy Transmission Grating Spectrometer and Low Energy Transmission Grating Spectrometer observations for a total exposure time of 800 ks. The continuum emission (between 0.2 keV and 8 keV) is well represented by a power law (Γ = 1.6) plus a blackbody component (kT = 0.1 keV). We find that the well-known X-ray warm absorber (WA) in this source consists of two different outflow velocity systems. One absorbing system has a velocity of -1110 ± 150 km s-1 and the other of -490 ± 150 km s-1. Recognizing the presence of these kinematically distinct components allows each system to be fitted independently, each with two absorption components with different ionization levels. The high-velocity system consists of two components, one with a temperature of 2.7 ± 0.6 × 106 K, log U = 1.23, and another with a temperature of 5.8 ± 1.0 × 105 K, log U = 0.67. The high-velocity, high-ionization component produces absorption by charge states Fe XXI-XXIV, while the high-velocity, low-ionization component produces absorption by Ne IX-X, Fe XVII-XX, and O VII-VIII. The low-velocity system also required two absorbing components, one with a temperature of 5.8 ± 0.8 × 105 K, log U = 0.67, producing absorption by Ne IX-X, Fe XVII-XX, and O VII-VIII, and the other with a lower temperature of 3.5 ± 0.35 × 104 K and a lower ionization of log U = -0.49, producing absorption by O VI-VII and the Fe VII-XII M-shell Unresolved Transitions Array. Once these components are considered, the data do not require any further absorbers. In particular, a model consisting of a continuous radial range of ionization structures (as suggested by a previous analysis) is not required. The two absorbing components in each velocity system are in pressure equilibrium with each other. This suggests that each velocity system consists of a multi-phase medium. This is the first time that
THE TWO-PHASE, TWO-VELOCITY IONIZED ABSORBER IN THE SEYFERT 1 GALAXY NGC 5548
Andrade-Velazquez, Mercedes; Krongold, Yair; Binette, Luc; Jimenez-Bailon, Elena; Elvis, Martin; Nicastro, Fabrizio; Brickhouse, Nancy; Mathur, Smita
2010-03-10
We present an analysis of X-ray high-quality grating spectra of the Seyfert 1 galaxy NGC 5548 using archival Chandra-High Energy Transmission Grating Spectrometer and Low Energy Transmission Grating Spectrometer observations for a total exposure time of 800 ks. The continuum emission (between 0.2 keV and 8 keV) is well represented by a power law (GAMMA = 1.6) plus a blackbody component (kT = 0.1 keV). We find that the well-known X-ray warm absorber (WA) in this source consists of two different outflow velocity systems. One absorbing system has a velocity of -1110 +- 150 km s{sup -1} and the other of -490 +- 150 km s{sup -1}. Recognizing the presence of these kinematically distinct components allows each system to be fitted independently, each with two absorption components with different ionization levels. The high-velocity system consists of two components, one with a temperature of 2.7 +- 0.6 x 10{sup 6} K, log U = 1.23, and another with a temperature of 5.8 +- 1.0 x 10{sup 5} K, log U = 0.67. The high-velocity, high-ionization component produces absorption by charge states Fe XXI-XXIV, while the high-velocity, low-ionization component produces absorption by Ne IX-X, Fe XVII-XX, and O VII-VIII. The low-velocity system also required two absorbing components, one with a temperature of 5.8 +- 0.8 x 10{sup 5} K, log U = 0.67, producing absorption by Ne IX-X, Fe XVII-XX, and O VII-VIII, and the other with a lower temperature of 3.5 +- 0.35 x 10{sup 4} K and a lower ionization of log U = -0.49, producing absorption by O VI-VII and the Fe VII-XII M-shell Unresolved Transitions Array. Once these components are considered, the data do not require any further absorbers. In particular, a model consisting of a continuous radial range of ionization structures (as suggested by a previous analysis) is not required. The two absorbing components in each velocity system are in pressure equilibrium with each other. This suggests that each velocity system consists of a multi-phase
Franceschini, Alexandre; Filippidi, Emmanouela; Guazzelli, Elisabeth; Pine, David J
2011-12-16
Shearing solutions of fibers or polymers tends to align fiber or polymers in the flow direction. Here, non-Brownian rods subjected to oscillatory shear align perpendicular to the flow while the system undergoes a nonequilibrium absorbing phase transition. The slow alignment of the fibers can drive the system through the critical point and thus promote the transition to an absorbing state. This picture is confirmed by a universal scaling relation that collapses the data with critical exponents that are consistent with conserved directed percolation. PMID:22243062
Nonlocal effects on the polarization state of a photon, induced by distant absorbers
NASA Technical Reports Server (NTRS)
Ryff, Luis Carlos B.
1994-01-01
A variant of a Franson's two-photon correlation experiment is discussed, in which the linear polarization state of one of the photons depends on the path followed in the interferometer. It is shown that although the path difference is greater than the coherence length, the photon can be found in a polarization state represented by the superposition of the polarization states associated to the paths when there is coincident detection. Since the photons, produced via parametric down-conversion, are fairly well localized in space and time, the situation in which one of the photons is detected before the other can reach the interferometer raises an intriguing point: it seems that in some cases the second photon would have to be described by two wave packets simultaneously. Unlike previous experiments, in which nonlocal effects were induced by means of polarizers of phase shifters, in the proposed experiment nonlocal effects can be induced by means of variable absorbers.
Absorbing states in a catalysis model with anti-Arrhenius behavior.
de Andrade, M F; Figueiredo, W
2012-04-28
We study a model of heterogeneous catalysis with competitive reactions between two monomers A and B. We assume that reactions are dependent on temperature and follow an anti-Arrhenius mechanism. In this model, a monomer A can react with a nearest neighbor monomer A or B, however, reactions between monomers of type B are not allowed. We assume attractive interactions between nearest neighbor monomers as well as between monomers and the catalyst. Through mean-field calculations, at the level of site and pair approximations, and extensive Monte Carlo simulations, we determine the phase diagram of the model in the plane y(A) versus temperature, where y(A) is the probability that a monomer A reaches the catalyst. The model exhibits absorbing and active phases separated by lines of continuous phase transitions. We calculate the static, dynamic, and spreading exponents of the model, and despite the absorbing state be represented by many different microscopic configurations, the model belongs to the directed percolation universality class in two dimensions. Both reaction mechanisms, Arrhenius and anti-Arrhenius, give the same set of critical exponents and do not change the nature of the universality class of the catalytic models. PMID:22559491
Phase diagrams of orientational transitions in absorbing nematic liquid crystals
Zolot’ko, A. S. Ochkin, V. N.; Smayev, M. P.; Shvetsov, S. A.
2015-05-15
A theory of orientational transitions in nematic liquid crystals (NLCs), which employs the expansion of optical torques acting on the NLC director with respect to the rotation angle, has been developed for NLCs with additives of conformationally active compounds under the action of optical and low-frequency electric and magnetic fields. Phase diagrams of NLCs are constructed as a function of the intensity and polarization of the light field, the strength of low-frequency electric field, and a parameter that characterizes the feedback between the rotation of the NLC director and optical torque. Conditions for the occurrence of first- and second-order transitions are determined. The proposed theory agrees with available experimental data.
Modeling electron dynamics coupled to continuum states in finite volumes with absorbing boundaries
NASA Astrophysics Data System (ADS)
De Giovannini, Umberto; Larsen, Ask Hjorth; Rubio, Angel
2015-03-01
Absorbing boundaries are frequently employed in real-time propagation of the Schrödinger equation to remove spurious reflections and efficiently emulate outgoing boundary conditions. These conditions are a fundamental ingredient for the calculation of observables involving infinitely extended continuum states in finite volumes. In the literature, several boundary absorbers have been proposed. They mostly fall into three main families: mask function absorbers, complex absorbing potentials, and exterior complex-scaled potentials. To date none of the proposed absorbers is perfect, and all present a certain degree of reflections. Characterization of such reflections is thus a critical task with strong implications for time-dependent simulations of atoms and molecules. We introduce a method to evaluate the reflection properties of a given absorber and present a comparison of selected samples for each family of absorbers. Further, we discuss the connections between members of each family and show how the same reflection curves can be obtained with very different absorption schemes.
Argolo, C; Quintino, Yan; Siqueira, Y; Gleria, Iram; Lyra, M L
2009-12-01
In this work, we study the critical behavior of a one-dimensional model that mimics the propagation of an epidemic process mediated by a density of diffusive individuals which can infect a static population upon contact. We simulate the above model on linear chains to determine the critical density of the diffusive population, above which the system achieves a statistically stationary active state, as a function of two relevant parameters related to the average lifetimes of the diffusive and nondiffusive populations. A finite-size scaling analysis is employed to determine the order parameter and correlation length critical exponents. For high-recovery rates, the critical exponents are compatible with the usual directed percolation universality class. However, in the opposite regime of low-recovery rates, the diffusion is a relevant mechanism responsible for the propagation of the disease and the absorbing state phase transition is governed by a distinct set of critical exponents. PMID:20365138
Parasitic oscillation suppression in solid state lasers using absorbing thin films
Zapata, L.E.
1994-08-02
A thin absorbing film is bonded onto at least certain surfaces of a solid state laser gain medium. An absorbing metal-dielectric multilayer film is optimized for a broad range of incidence angles, and is resistant to the corrosive/erosive effects of a coolant such as water, used in the forced convection cooling of the film. Parasitic oscillations hamper the operation of solid state lasers by causing the decay of stored energy to amplified rays trapped within the gain medium by total and partial internal reflections off the gain medium facets. Zigzag lasers intended for high average power operation require the ASE absorber. 16 figs.
Parasitic oscillation suppression in solid state lasers using absorbing thin films
Zapata, Luis E.
1994-01-01
A thin absorbing film is bonded onto at least certain surfaces of a solid state laser gain medium. An absorbing metal-dielectric multilayer film is optimized for a broad range of incidence angles, and is resistant to the corrosive/erosive effects of a coolant such as water, used in the forced convection cooling of the film. Parasitic oscillations hamper the operation of solid state lasers by causing the decay of stored energy to amplified rays trapped within the gain medium by total and partial internal reflections off the gain medium facets. Zigzag lasers intended for high average power operation require the ASE absorber.
Peng, Pei; Wang, Wei; Zhang, Li; Su, Shiguang; Wang, Jiahui
2013-12-01
The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas-permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r(2)>0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min(-1), the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC=0.0267c+0.0351 (AU min(-1)), with r(2)=0.9922 within concentrations of 0.5-3.0 mg L(-1). The relative error for 0.5 mg L(-1) benzene (n=6) is 7.4±3.7%, and the LOD is 0.04 mg L(-1). This research can provide theoretical and practical guides for liquid-phase gas sensor design and development based on a
Renormalisation of 2D Cellular Automata with an Absorbing State
NASA Astrophysics Data System (ADS)
Weaver, Iain S.; Prügel-Bennett, Adam
2015-04-01
We describe a real-space renormalisation scheme for non-equilibrium probabilistic cellular automata (PCA) models, and apply it to a two-dimensional binary PCA. An exact renormalisation scheme is rare, and therefore we provide a method for computing the stationary probability distribution of states for such models with which to weight the renormalisation, effectively minimising the error in the scale transformation. While a mean-field approximation is trivial, we use the principle of maximum entropy to incorporate nearest-neighbour spin-correlations in the steady-state probability distribution. In doing so we find the fixed point of the renormalisation is modified by the steady-state approximation order.
Carrillo, Santiago García-Cuevas; Nash, Geoffrey R; Hayat, Hasan; Cryan, Martin J; Klemm, Maciej; Bhaskaran, Harish; Wright, C David
2016-06-13
Phase-change chalcogenide alloys, such as Ge_{2}Sb_{2}Te_{5} (GST), have very different optical properties in their amorphous and crystalline phases. The fact that such alloys can be switched, optically or electrically, between such phases rapidly and repeatedly means that they have much potential for applications as tunable photonic devices. Here we incorporate chalcogenide phase-change films into a metal-dielectric-metal metamaterial electromagnetic absorber structure and design absorbers and modulators for operation at technologically important near-infrared wavelengths, specifically 1550 nm. Our design not only exhibits excellent performance (e.g. a modulation depth of ~77% and an extinction ratio of ~20 dB) but also includes a suitable means for protecting the GST layer from environmental oxidation and is well-suited, as confirmed by electro-thermal and phase-transformation simulations, to in situ electrical switching. We also present a systematic study of design optimization, including the effects of expected manufacturing tolerances on device performance and, by means of a sensitivity analysis, identify the most critical design parameters. PMID:27410372
NASA Astrophysics Data System (ADS)
Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray
2015-08-01
Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing.
Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray
2015-01-01
Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing. PMID:26294085
Nanostructured thin film-based near-infrared tunable perfect absorber using phase-change material
NASA Astrophysics Data System (ADS)
Kocer, Hasan
2015-01-01
Nanostructured thin film absorbers embedded with phase-change thermochromic material can provide a large level of absorption tunability in the near-infrared region. Vanadium dioxide was employed as the phase-change material in the designed structures. The optical absorption properties of the designed structures with respect to the geometric and material parameters were systematically investigated using finite-difference time-domain computations. Absorption level of the resonance wavelength in the near-IR region was tuned from the perfect absorption level to a low level (17%) with a high positive dynamic range of near-infrared absorption intensity tunability (83%). Due to the phase transition of vanadium dioxide, the resonance at the near-infrared region is being turned on and turned off actively and reversibly under the thermal bias, thereby rendering these nanostructures suitable for infrared camouflage, emitters, and sensors.
Phase Operator and Phase State in Thermo Field Dynamics
NASA Astrophysics Data System (ADS)
Fan, Hong-Yi; Jiang, Nian-Quan
We extend the Susskind-Glogower phase operator and phase state in quantum optics to thermo field dynamics (TFD). Based on the thermo entangled state representation, we introduce thermo excitation and de-excitation operators with which the phase operator and phase state in TFD can be constructed. The phase state treated as a limiting case of a new SU(1, 1) coherent states is also exhibited.
Effect of diffusion in one-dimensional discontinuous absorbing phase transitions.
Fiore, Carlos E; Landi, Gabriel T
2014-09-01
It is known that diffusion provokes substantial changes in continuous absorbing phase transitions. Conversely, its effect on discontinuous transitions is much less understood. In order to shed light in this direction, we study the inclusion of diffusion in the simplest one-dimensional model with a discontinuous absorbing phase transition, namely, the long-range contact process (σ-CP). Particles interact as in the usual CP, but the transition rate depends on the length ℓ of inactive sites according to 1+aℓ(-σ), where a and σ are control parameters. The inclusion of diffusion in this model has been investigated by numerical simulations and mean-field calculations. Results show that there exists three distinct regimes. For sufficiently low and large σ's the transition is, respectively, always discontinuous or continuous, independently of the strength of the diffusion. On the other hand, in an intermediate range of σ's, the diffusion causes a suppression of the phase coexistence leading to a continuous transition belonging to the directed percolation universality class. PMID:25314411
Effect of diffusion in one-dimensional discontinuous absorbing phase transitions
NASA Astrophysics Data System (ADS)
Fiore, Carlos E.; Landi, Gabriel T.
2014-09-01
It is known that diffusion provokes substantial changes in continuous absorbing phase transitions. Conversely, its effect on discontinuous transitions is much less understood. In order to shed light in this direction, we study the inclusion of diffusion in the simplest one-dimensional model with a discontinuous absorbing phase transition, namely, the long-range contact process (σ-CP). Particles interact as in the usual CP, but the transition rate depends on the length ℓ of inactive sites according to 1+aℓ-σ, where a and σ are control parameters. The inclusion of diffusion in this model has been investigated by numerical simulations and mean-field calculations. Results show that there exists three distinct regimes. For sufficiently low and large σ's the transition is, respectively, always discontinuous or continuous, independently of the strength of the diffusion. On the other hand, in an intermediate range of σ's, the diffusion causes a suppression of the phase coexistence leading to a continuous transition belonging to the directed percolation universality class.
Influence of competition in minimal systems with discontinuous absorbing phase transitions
NASA Astrophysics Data System (ADS)
Pianegonda, Salete; Fiore, Carlos E.
2016-06-01
Contact processes (CP's) with particle creation requiring a minimal neighborhood (restrictive or threshold CP's) present a novel sort of discontinuous absorbing transitions, that revealed itself robust under the inclusion of different ingredients, such as distinct lattice topologies, particle annihilations and diffusion. Here, we tackle on the influence of competition between restrictive and standard dynamics (that describes the usual CP and a continuous DP transition is presented). Systems have been studied via mean-field theory (MFT) and numerical simulations. Results show partial contrast between MFT and numerical results. While the former predicts that considerable competition rates are required to shift the phase transition, the latter reveals the change occurs for rather limited (small) fractions. Thus, unlike previous ingredients (such as diffusion and others), limited competitive rates suppress the phase coexistence.
NASA Astrophysics Data System (ADS)
Zolotovskii, I. O.; Korobko, D. A.; Gumenyuk, R. V.; Okhotnikov, O. G.
2015-01-01
A numerical model of a soliton fibre laser with a semiconductor saturable absorber mirror (SESAM), characterised by the complex dynamics of absorption relaxation, is considered. It is shown that stationary bound states of pulses can be formed in this laser as a result of their interaction via the dispersion-wave field. The stability of stationary bound states of several pulses is analysed. It is shown that an increase in the number of pulses in a stationary bound state leads eventually to its decay and formation of a random bunch. It is found that the bunch stability is caused by the manifestation of nonlinear self-phase modulation, which attracts pulses to the bunch centre. The simulation results are in qualitative agreement with experimental data.
Zolotovskii, I O; Korobko, D A; Okhotnikov, O G; Gumenyuk, R V
2015-01-31
A numerical model of a soliton fibre laser with a semiconductor saturable absorber mirror (SESAM), characterised by the complex dynamics of absorption relaxation, is considered. It is shown that stationary bound states of pulses can be formed in this laser as a result of their interaction via the dispersion-wave field. The stability of stationary bound states of several pulses is analysed. It is shown that an increase in the number of pulses in a stationary bound state leads eventually to its decay and formation of a random bunch. It is found that the bunch stability is caused by the manifestation of nonlinear self-phase modulation, which attracts pulses to the bunch centre. The simulation results are in qualitative agreement with experimental data. (nonlinear optical phenomena)
Wang, Hao; Yang, Yue; Wang, Liping
2014-08-18
We numerically demonstrate a switchable metamaterial absorber/emitter by thermally turning on or off the excitation of magnetic resonance upon the phase transition of vanadium dioxide (VO{sub 2}). Perfect absorption peak exists around the wavelength of 5 μm when the excitation of magnetic resonance is supported with the insulating VO{sub 2} spacer layer. The wavelength-selective absorption is switched off when the magnetic resonance is disabled with metallic VO{sub 2} that shorts the top and bottom metallic structures. The resonance wavelength can be tuned with different geometry, and the switchable metamaterial exhibits diffuse behaviors at oblique angles. The results would facilitate the design of switchable metamaterials for active control in energy and sensing applications.
NASA Astrophysics Data System (ADS)
Wang, Hao; Yang, Yue; Wang, Liping
2014-08-01
We numerically demonstrate a switchable metamaterial absorber/emitter by thermally turning on or off the excitation of magnetic resonance upon the phase transition of vanadium dioxide (VO2). Perfect absorption peak exists around the wavelength of 5 μm when the excitation of magnetic resonance is supported with the insulating VO2 spacer layer. The wavelength-selective absorption is switched off when the magnetic resonance is disabled with metallic VO2 that shorts the top and bottom metallic structures. The resonance wavelength can be tuned with different geometry, and the switchable metamaterial exhibits diffuse behaviors at oblique angles. The results would facilitate the design of switchable metamaterials for active control in energy and sensing applications.
Experimental evidence for an absorbing phase transition underlying yielding of a soft glass
NASA Astrophysics Data System (ADS)
Nagamanasa, K. Hima; Gokhale, Shreyas; Sood, A. K.; Ganapathy, Rajesh
2014-03-01
A characteristic feature of solids ranging from foams to atomic crystals is the existence of a yield point, which marks the threshold stress beyond which a material undergoes plastic deformation. In hard materials, it is well-known that local yield events occur collectively in the form of intermittent avalanches. The avalanche size distributions exhibit power-law scaling indicating the presence of self-organized criticality. These observations led to predictions of a non-equilibrium phase transition at the yield point. By contrast, for soft solids like gels and dense suspensions, no such predictions exist. In the present work, by combining particle scale imaging with bulk rheology, we provide a direct evidence for a non-equilibrium phase transition governing yielding of an archetypal soft solid - a colloidal glass. The order parameter and the relaxation time exponents revealed that yielding is an absorbing phase transition that belongs to the conserved directed percolation universality class. We also identified a growing length scale associated with clusters of particles with high Debye-Waller factor. Our findings highlight the importance of correlations between local yield events and may well stimulate the development of a unified description of yielding of soft solids.
Limit pulses in passive nonlinear absorbers. [solid-state laser materials
NASA Technical Reports Server (NTRS)
Lee, C. T.
1974-01-01
The propagation of coherent pulses in absorbers with nonlinear refractive index is investigated. It is shown that a term neglected by previous authors places an upper limit on the attainable field strength in steady-state pulses. In ruby with a Cr(3+) doping density of 10 to the 17th power per cu cm, for example, this limit is less than 2,000,000 V/cm.
NASA Astrophysics Data System (ADS)
Monjushiro, Hideaki; Tanaka, Makiko; Watarai, Hitoshi
2005-08-01
Laser-photophretic behavior of the micrometer-sized single droplets of photo-absorbing microemulsion was observed in water by irradiating a cw Ar+ ion laser. We have made an unexpected observation that the droplets repeated the expansion and the sudden contraction motion during the laser photophoretic migration. The period of the expansion-contraction cycle was decreased as the irradiated laser power was increased and was independent of the initial size of the droplet. The origin of the cyclical motion is the temperature rise of the droplet due to the photo-thermal conversion. The three-step mechanism for the periodic motion of the droplet was proposed. The first step is the phase separation of the bicontinuous microemulsion droplet into the normal w/o microemulsion outer phase and the aqueous inner phase in the droplet, which was caused by the laser-induced temperature gradient inside the droplet. In the second step, an expansion of the inner aqueous phase was induced by the percolation of the external water by thermo-osmosis, which was caused by the laser-induced temperature gradient between inside and outside of the microemulsion liquid membrane of the droplet. In the third step, the liquid membrane became thinner to a critical thickness which induced its break and the droplet shrank into the original shape. The proposed mechanism for the expansion process was confirmed by the numerical simulation of the volume change of the droplet during the laser irradiation, taking account of the heat evolution in the droplet, the heat transfer from the droplet, and the percolation of the external water by thermo-osmosis and by the high-speed CCD imaging of the contraction motion of the droplet.
A partial eclipse of the heart: the absorbed X-ray low state in Mrk 1048
NASA Astrophysics Data System (ADS)
Parker, M. L.; Schartel, N.; Komossa, S.; Grupe, D.; Santos-Lleó, M.; Fabian, A. C.; Mathur, S.
2014-11-01
We present two new XMM-Newton observations of an unprecedented low-flux state in the Seyfert 1 Mrk 1048 (NGC 985), taken in 2013. The X-ray flux below 1 keV drops by a factor of 4-5, whereas the spectrum above 5 keV is essentially unchanged. This points towards an absorption origin for the low state, and we confirm this with spectral fitting, finding that the spectral differences can be well modelled by the addition of a partial covering neutral absorber, with a column density of ˜3 × 1022 cm-2 and a covering fraction of ˜0.6. The optical and UV fluxes are not affected, and indeed are marginally brighter in the more recent observations, suggesting that only the inner regions of the disc are affected by the absorption event. This indicates either that the absorption is due to a cloud passing over the inner disc, obscuring the X-ray source but leaving the outer disc untouched, or that the absorber is dust-free so the UV continuum is unaffected. We use arguments based on the duration of the event and the physical properties of the absorber to constrain its size and location, and conclude that it is most likely a small cloud at ˜1018 cm from the source.
Nonadditive Mixed State Phases in Neutron Optics
Klepp, J.; Sponar, S.; Filipp, S.; Lettner, M.; Badurek, G.; Hasegawa, Y.
2009-03-10
In a neutron polarimetry experiment mixed neutron spin phases are determined. We consider evolutions leading to purely geometric, purely dynamical and combined phases. It is experimentally demonstrated that the sum of the geometric and dynamical phases--both obtained in separate measurements--is not equal to the associated total phase as obtained from a third measurement, unless the system is in a pure state. In this sense, mixed state phases are not additive.
Femtosecond solid-state laser based on a few-layered black phosphorus saturable absorber.
Su, Xiancui; Wang, Yiran; Zhang, Baitao; Zhao, Ruwei; Yang, Kejian; He, Jingliang; Hu, Qiangqiang; Jia, Zhitai; Tao, Xutang
2016-05-01
In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers. PMID:27128045
Photoexcited singlet and triplet states of a UV absorber ethylhexyl methoxycrylene.
Kikuchi, Azusa; Hata, Yuki; Kumasaka, Ryo; Nanbu, Yuichi; Yagi, Mikio
2013-01-01
The excited states of UV absorber, ethylhexyl methoxycrylene (EHMCR) have been studied through measurements of UV absorption, fluorescence, phosphorescence and electron paramagnetic resonance (EPR) spectra in ethanol. The energy levels of the lowest excited singlet (S1) and triplet (T1) states of EHMCR were determined. The energy levels of the S1 and T1 states of EHMCR are much lower than those of photolabile 4-tert-butyl-4'-methoxydibenzoylmethane. The energy levels of the S1 and T1 states of EHMCR are lower than those of octyl methoxycinnamate. The weak phosphorescence and EPR B(min) signals were observed and the lifetime was estimated to be 93 ms. These facts suggest that the significant proportion of the S1 molecules undergoes intersystem crossing to the T1 state, and the deactivation process from the T1 state is predominantly radiationless. The photostability of EHMCR arises from the (3)ππ* character in the T1 state. The zero-field splitting (ZFS) parameter in the T1 state is D** = 0.113 cm(-1). PMID:23136952
Graphene saturable absorber mirror for ultra-fast-pulse solid-state laser.
Xu, Jin-Long; Li, Xian-Lei; Wu, Yong-Zhong; Hao, Xiao-Peng; He, Jing-Liang; Yang, Ke-Jian
2011-05-15
High-quality graphene sheets with lateral size over 20 μm have been obtained by bath sonicating after subjecting the wormlike graphite marginally to mixed oxidizer. To date, to our knowledge, they are the largest graphene sheets prepared by exfoliation in the liquid phase. A saturable absorber mirror was fabricated based on these sheets. We exploited it to realize mode-locking operation in a diode-pumped Nd:GdVO(4) laser. A pulse duration of 16 ps was produced with an average power of 360 mW and a highest pulse energy of 8.4 nJ for a graphene mode-locked laser. PMID:21593945
Entanglement of phase-random states
NASA Astrophysics Data System (ADS)
Nakata, Yoshifumi; Turner, Peter; Murao, Mio
2014-12-01
In order to study generic properties of time-evolving states by time-independent Hamiltonian dynamics, we introduce phase-random states, an ensemble of pure states with fixed amplitudes and uniformly distributed phases in a fixed basis. We compute the average amount of entanglement of phase-random states analytically, and show that the average can be extremely large when the amplitudes are equal and the basis is separable. We also study implications on Hamiltonian dynamics, in particular the realization of the canonical state in a subsystem.
NASA Astrophysics Data System (ADS)
Xu, S. C.; Man, B. Y.; Jiang, S. Z.; Chen, C. S.; Liu, M.; Yang, C.; Gao, S. B.; Feng, D. J.; Hu, G. D.; Huang, Q. J.; Chen, X. F.; Zhang, C.
2014-08-01
We present a novel method for the direct metal-free growth of graphene on quartz substrate. The direct-grown graphene yields excellent nonlinear saturable absorption properties and is demonstrated to be suitable as a saturable absorber (SA) for an ultrafast solid-state laser. Nearly Fourier-limited 367 fs was obtained at a central wavelength of 1048 nm with a repetition rate of 105.7 MHz. At a pump power of 7.95 W, the average output power was 1.93 W and the highest pulse energy reached 18.3 nJ, with a peak power of 49.8 kW. Our work opens an easy route for making a reliable graphene SA with a mode-locking technique and also displays an exciting prospect in making low-cost and ultrafast lasers.
Solid state saturable absorbers for Q-switching at 1 and 1.3μm: investigation and modeling
NASA Astrophysics Data System (ADS)
Šulc, Jan; Arátor, Pavel; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav; Kokta, Milan R.
2008-02-01
Yttrium and Lutecium garnets (YAG and LuAG) doped by Chromium or Vanadium ions (Cr 4+ or V 3+) were investigated as saturable absorbers potentially useful for passive Q-switching at wavelengths 1 μm and/or 1.3 μm. For comparison also color center saturable absorber LiF:F - II and Cobalt doped spinel (Co:MALO) were studied. Firstly, low power absorption spectra were recorded for all samples. Next, absorbers transmission in dependence on incident energy/power density was measured using the z-scan method. Crystals Cr:YAG, Cr:LuAG, V:YAG, and LiF:F - II were tested at wavelength 1064 nm. Therefore Alexandrite laser pumped Q-switched Nd:YAG laser was used as a radiation source (pulse length 6.9 ns, energy up to 1.5 mJ). Crystals V:YAG, V:LuAG, and Co:MALO were tested at wavelength 1338 nm. So diode pumped Nd:YAG/V:YAG microchip laser was used as a radiation source (pulse length 6.2 ns, energy up to 0.1 mJ). Using measured data fitting, and by their comparison with numerical model of a "thick" saturable absorber transmission for Q-switched Gaussian laser beam, following parameters were estimated: saturable absorber initial transmission T 0, saturation energy density w s, ground state absorption cross-section σ GSA, saturated absorber transmission T s, excited state absorption cross-section σ ESA, ratio γ = σ GSA/σ ESA, and absorbing ions density. For V:YAG crystal, a polarization dependence of T s was also investigated. With the help of rate equation numerical solution, an impact of saturable absorber parameters on generated Q-switched pulse properties was studied in plane wave approximation. Selected saturable absorbers were also investigated as a Q-switch and results were compared with the model.
Cornilescu, Gabriel; Ulijasz, Andrew T; Cornilescu, Claudia C; Markley, John L; Vierstra, Richard D
2008-11-01
The unique photochromic absorption behavior of phytochromes (Phys) depends on numerous reversible interactions between the bilin chromophore and the associated polypeptide. To help define these dynamic interactions, we determined by NMR spectroscopy the first solution structure of the chromophore-binding cGMP phosphodiesterase/adenylcyclase/FhlA (GAF) domain from a cyanobacterial Phy assembled with phycocyanobilin (PCB). The three-dimensional NMR structure of Synechococcus OS-B' cyanobacterial Phy 1 in the red-light-absorbing state of Phy (Pr) revealed that PCB is bound to Cys138 of the GAF domain via the A-ring ethylidene side chain and is buried within the GAF domain in a ZZZsyn,syn,anti configuration. The D ring of the chromophore sits within a hydrophobic pocket and is tilted by approximately 80 degrees relative to the B/C rings by contacts with Lys52 and His169. The solution structure revealed remarkable flexibility for PCB and several adjacent amino acids, indicating that the Pr chromophore has more freedom in the binding pocket than anticipated. The propionic acid side chains of rings B and C and Arg101 and Arg133 nearby are especially mobile and can assume several distinct and energetically favorable conformations. Mutagenic studies on these arginines, which are conserved within the Phy superfamily, revealed that they have opposing roles, with Arg101 and Arg133 helping stabilize and destabilize the far-red-light-absorbing state of Phy (Pfr), respectively. Given the fact that the Synechococcus OS-B' GAF domain can, by itself, complete the Pr --> Pfr photocycle, it should now be possible to determine the solution structure of the Pfr chromophore and surrounding pocket using this Pr structure as a framework. PMID:18762196
Felhofer, Jessica L; Scida, Karen; Penick, Mark; Willis, Peter A; Garcia, Carlos D
2013-10-15
To overcome the problem of poor sensitivity of capillary electrophoresis-UV absorbance for the detection of aliphatic amines, a solid phase extraction and derivatization scheme was developed. This work demonstrates successful coupling of amines to a chromophore immobilized on a solid phase and subsequent cleavage and analysis. Although the analysis of many types of amines is relevant for myriad applications, this paper focuses on the derivatization and separation of amines with environmental relevance. This work aims to provide the foundations for future developments of an integrated sample preparation microreactor capable of performing simultaneous derivatization, preconcentration, and sample cleanup for sensitive analysis of primary amines. PMID:24054648
Felhofer, Jessica L.; Scida, Karen; Penick, Mark; Willis, Peter A.; Garcia, Carlos D.
2013-01-01
To overcome the problem of poor sensitivity of capillary electrophoresis-UV absorbance for the detection of aliphatic amines, a solid phase extraction and derivatization scheme was developed. This work demonstrates successful coupling of amines to a chromophore immobilized on a solid phase and subsequent cleavage and analysis. Although the analysis of many types of amines is relevant for myriad applications, this paper focuses on the derivatization and separation of amines with environmental relevance. This work aims to provide the foundations for future developments of an integrated sample preparation microreactor capable of performing simultaneous derivatization, preconcentration, and sample cleanup for sensitive analysis of primary amines. PMID:24054648
Super-absorbency and phase transition of gels in physiological salt solutions
NASA Astrophysics Data System (ADS)
Zhang, Yong-Qing; Tanaka, Toyoichi; Shibayama, Mitsuhiro
1992-11-01
IONIC gels with the ability to absorb many times their dry weight of water have found widespread use as absorbents in medical, chemical and agricultural applications1. The dramatic swelling power of these super-absorbent gels results from both the electrostatic repulsion between the charges on the polymer chains, and the osmotic pressure of the counter-ions2. In salt solutions such as saline, urine or blood, however, excess Na+ and Cl- ions screen the polymer charges and eliminate the osmotic imbalance, effectively changing the properties of the material to that of a non-ionic gel3: this greatly diminishes the swelling power, and hence the utility of these materials under physiological conditions. Here we report the development of a system combining a non-ionic gel with ionized surfactants, which shows super-absorbent behaviour even in the presence of salt. In water, the hydrophobic gel facilitates the formation of spherical surfactant micelles, which mimic the charged sites of an ionic gel. As the salt concentration is increased, the micelles become rod-like, maintaining the electrostatic repulsion along the polymer chains and thereby preserving the swelling power of the gel.
Mode-locking of solid-state lasers by single-walled carbon-nanotube based saturable absorbers
Rotermund, F; Cho, W B; Choi, S Y; Baek, I H; Yim, J H; Lee, S; Schmidt, A; Steinmeyer, G; Griebner, U; Yeom, D I; Kim, K; Petrov, V
2012-08-31
Universal use of single-walled carbon-nanotube based saturable absorber devices for mode-locking of bulk solid-state lasers between 0.8 and 2 {mu}m is discussed. The advantages in comparison to semiconductor saturable absorbers are emphasised. We briefly describe the manufacturing process and the essential optical properties, and review experimental results obtained with various types of femtosecond and picosecond solid-state lasers in the steady-state regime. We also demonstrate that a single hybrid saturable absorber used in transmission can be used to mode-lock four different types of lasers operating between 1 and 2 {mu}m. (control of laser radiation parameters)
Particle Rebound and Phase State of Secondary Organic Material
NASA Astrophysics Data System (ADS)
Bateman, A.; Bertram, A. K.; Martin, S. T.
2014-12-01
Secondary organic material (SOM) is produced in the atmosphere from the oxidation of volatile organic compounds emitted from anthropogenic and biogenic sources. Aerosol particles, composed in part of SOM, play important roles in climate and air quality by scattering/absorbing radiation and serving as cloud condensation nuclei (CCN). The magnitude of climate-relevant perturbations depends on particle chemical composition, hygroscopic growth, and phase state, among other factors. Herein, the hygroscopic influence on particle rebound and the phase state of particles composed of isoprene, toluene, and α-pinene secondary organic material (SOM) was studied. Particle rebound measurements were obtained from 5 to 95% RH using a three-arm impaction apparatus. The experimentally determined rebound fractions were compared with results from a model of the rebound process that took into account the particle kinetic energy, van der Waals forces, and RH-dependent capillary forces. Comparison of the experimental and modeled indicated particles softened due to water uptake. For low RH values, the model explained the rebound behavior for all studied SOMs. At higher RH values specific to each SOM, however, particle rebound was no longer observed, and the model did not capture this behavior. Calibration experiments using sucrose particles of variable known viscosities showed the transition from non-rebounding to rebounding particles occurred for viscosity values from 100 to 1 Pa s, corresponding to a transition from semisolid to liquid material. The implication of the differing RH-dependent behaviors among the SOMs is that each SOM has a specific and quantitatively different interaction with water. A linear correlation between rebound fraction and hygroscopic growth factor was demonstrated, implying that absorbed water volume is the governing factor of viscosity for the studied classes of SOM. The findings of this study suggest that both the chemical composition and the ambient
Phase Transfer-Catalyzed Fast CO2 Absorption by MgO-Based Absorbents with High Cycling Capacity
Zhang, Keling; Li, Xiaohong S.; Li, Weizhen; Rohatgi, Aashish; Duan, Yuhua; Singh, Prabhakar; Li, Liyu; King, David L.
2014-06-01
CO2 capture from pre-combustion syngas in the temperature range of 250-400°C is highly desirable from an energy efficiency perspective. Thermodynamically, MgO is a promising material for CO2 capture, but the gas-solid reaction to produce MgCO3 is kinetically slow due to high lattice energy. We report here fast CO2 absorption over a solid MgO-molten nitrate/nitrite aggregate through phase transfer catalysis, in which the molten phase serves as both a catalyst and reaction medium. Reaction with CO2 at the gas-solid-liquid triple phase boundary results in formation of MgCO3 with significant reaction rate and a high conversion of MgO. This methodology is also applicable to other alkaline earth oxides, inspiring the design of absorbents which require activation of the bulk material.
Myoplasmic binding of fura-2 investigated by steady-state fluorescence and absorbance measurements.
Konishi, M; Olson, A; Hollingworth, S; Baylor, S M
1988-01-01
Binding of the fluorescent Ca2+ indicator dye fura-2 by intracellular constituents has been investigated by steady-state optical measurements. Fura-2's (a) fluorescence intensity, (b) fluorescence emission anisotropy, (c) fluorescence emission spectrum, and (d) absorbance spectra were measured in glass capillary tubes containing solutions of purified myoplasmic proteins; properties b and c were also measured in frog skeletal muscle fibers microinjected with fura-2. The results indicate that more than half, and possibly as much as 85%, of fura-2 molecules in myoplasm are in a protein-bound form, and that the binding changes many properties of the dye. For example, in vitro characterization of the Ca2+-dye reaction indicates that when fura-2 is bound to aldolase (a large and abundant myoplasmic protein), the dissociation constant of the dye for Ca2+ is three- to fourfold larger than that measured in the absence of protein. The problems raised by intracellular binding of fura-2 to cytoplasmic proteins may well apply to cells other than skeletal muscle fibers. PMID:3266079
Propagating confined states in phase dynamics
NASA Technical Reports Server (NTRS)
Brand, Helmut R.; Deissler, Robert J.
1992-01-01
Theoretical treatment is given to the possibility of the existence of propagating confined states in the nonlinear phase equation by generalizing stationary confined states. The nonlinear phase equation is set forth for the case of propagating patterns with long wavelengths and low-frequency modulation. A large range of parameter values is shown to exist for propagating confined states which have spatially localized regions which travel on a background with unique wavelengths. The theoretical phenomena are shown to correspond to such physical systems as spirals in Taylor instabilities, traveling waves in convective systems, and slot-convection phenomena for binary fluid mixtures.
Vahed, H.; Kheradmand, R.; Tajalli, H.; Tissoni, G.; Lugiato, L. A.; Prati, F.
2011-12-15
We numerically study the dynamics of pairs of cavity solitons in a laser. We show that the solitons interact even at distances much greater than their sizes in the intensity and carrier-densities profile. The interaction is mediated by the phase. In a certain range of initial values of the distance, the solitons adjust their position until they form bound states. There are two such bound states, corresponding to different equilibrium distances, in which the solitons display partial phase locking, that is, their relative phase slowly oscillates as in a phase-entrained state. In those states, the two solitons can be switched on and off independently. For smaller initial distances, only one soliton survives. For larger initial distances, the solitons lock in phase and repel each other up to a distance of about ten soliton diameters.
Hydration states of AFm cement phases
Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Wadsö, Lars
2015-07-15
The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.
Protected boundary states in gapless topological phases
NASA Astrophysics Data System (ADS)
Matsuura, Shunji; Chang, Po-Yao; Schnyder, Andreas P.; Ryu, Shinsei
2013-06-01
We systematically study gapless topological phases of (semi-)metals and nodal superconductors described by Bloch and Bogoliubov-de Gennes Hamiltonians. Using K-theory, a classification of topologically stable Fermi surfaces in (semi-)metals and nodal lines in superconductors is derived. We discuss a generalized bulk-boundary correspondence that relates the topological features of the Fermi surfaces and superconducting nodal lines to the presence of protected zero-energy states at the boundary of the system. Depending on the case, the boundary states are either linearly dispersing (i.e. Dirac or Majorana states) or dispersionless, forming two-dimensional surface flat bands or one-dimensional arc surface states. We study examples of gapless topological phases in symmetry classes AIII and DIII, focusing in particular on nodal superconductors, such as nodal noncentrosymmetric superconductors. For some cases we explicitly compute the surface spectrum and examine the signatures of the topological boundary states in the surface density of states. We also discuss the robustness of the surface states against disorder.
Lee, Sang Bub
2015-12-01
The absorbing phase transition of the modified conserved lattice gas (m-CLG) model was investigated in one dimension. The m-CLG model was modified from the conserved lattice gas (CLG) model in such a way that each active particle hops to one of the nearest-neighbor and next-nearest-neighbor empty sites. The order parameter exponent, the dynamic exponent, and the correlation length exponent were estimated from the power-law behavior and finite-size scaling of the active particle densities. The exponents were found to differ considerably from those of the ordinary CLG model and were also distinct from those of the Manna model, suggesting that next-nearest-neighbor hopping is a relevant factor that alters the critical behavior in the one-dimensional CLG model. PMID:26764627
Bench-Scale Process for Low-Cost Carbon Dioxide (CO2) Capture Using a Phase-Changing Absorbent
Westendorf, Tiffany; Caraher, Joel; Chen, Wei; Farnum, Rachael; Perry, Robert; Spiry, Irina; Wilson, Paul; Wood, Benjamin
2015-03-31
The objective of this project is to design and build a bench-scale process for a novel phase-changing aminosilicone-based CO2-capture solvent. The project will establish scalability and technical and economic feasibility of using a phase-changing CO2-capture absorbent for post-combustion capture of CO2 from coal-fired power plants with 90% capture efficiency and 95% CO2 purity at a cost of $40/tonne of CO2 captured by 2025 and a cost of <$10/tonne of CO2 captured by 2035. In the first budget period of this project, the bench-scale phase-changing CO2 capture process was designed using data and operating experience generated under a previous project (ARPA-e project DE-AR0000084). Sizing and specification of all major unit operations was completed, including detailed process and instrumentation diagrams. The system was designed to operate over a wide range of operating conditions to allow for exploration of the effect of process variables on CO2 capture performance.
Note: Gratings on low absorbing substrates for x-ray phase contrast imaging
NASA Astrophysics Data System (ADS)
Koch, F. J.; Schröter, T. J.; Kunka, D.; Meyer, P.; Meiser, J.; Faisal, A.; Khalil, M. I.; Birnbacher, L.; Viermetz, M.; Walter, M.; Schulz, J.; Pfeiffer, F.; Mohr, J.
2015-12-01
Grating based X-ray phase contrast imaging is on the verge of being applied in clinical settings. To achieve this goal, compact setups with high sensitivity and dose efficiency are necessary. Both can be increased by eliminating unwanted absorption in the beam path, which is mainly due to the grating substrates. Fabrication of gratings via deep X-ray lithography can address this issue by replacing the commonly used silicon substrate with materials with lower X-ray absorption that fulfill certain boundary conditions. Gratings were produced on both graphite and polymer substrates without compromising on structure quality. These gratings were tested in a three-grating setup with a source operated at 40 kVp and lead to an increase in the detector photon count rate of almost a factor of 4 compared to a set of gratings on silicon substrates. As the visibility was hardly affected, this corresponds to a significant increase in sensitivity and therefore dose efficiency.
Note: Gratings on low absorbing substrates for x-ray phase contrast imaging
Koch, F. J. Schröter, T. J.; Kunka, D.; Meyer, P.; Meiser, J.; Faisal, A.; Khalil, M. I.; Mohr, J.; Birnbacher, L.; Viermetz, M.; Pfeiffer, F.; Walter, M.; Schulz, J.
2015-12-15
Grating based X-ray phase contrast imaging is on the verge of being applied in clinical settings. To achieve this goal, compact setups with high sensitivity and dose efficiency are necessary. Both can be increased by eliminating unwanted absorption in the beam path, which is mainly due to the grating substrates. Fabrication of gratings via deep X-ray lithography can address this issue by replacing the commonly used silicon substrate with materials with lower X-ray absorption that fulfill certain boundary conditions. Gratings were produced on both graphite and polymer substrates without compromising on structure quality. These gratings were tested in a three-grating setup with a source operated at 40 kVp and lead to an increase in the detector photon count rate of almost a factor of 4 compared to a set of gratings on silicon substrates. As the visibility was hardly affected, this corresponds to a significant increase in sensitivity and therefore dose efficiency.
New Co-containing glass ceramics saturable absorbers for 1.5-μm solid state lasers
NASA Astrophysics Data System (ADS)
Malyarevich, Alexander M.; Denisov, Igor A.; Yumashev, Konstantin V.; Chuvaeva, Tamara I.; Dymshits, Olga S.; Onushchenko, Alexei A.; Zhilin, Alexander A.
2001-03-01
New saturable absorber Q-switch for 1.54 %mum Er: glass laser is present. The saturable absorber is transparent glass ceramic containing magnesium-aluminum spinel nanocrystallites doped with tetrahedrally coordinated Co2+ ions. Q-switched pulses of up to 5.5 mJ in energy and 80 ns in duration at 1.54 micrometers were achieved. Relaxation time of the 4A2 to 4T1(4F) transition bleaching was measured to be (450+/- 150)ns. Ground-state absorption cross-sections at 1.54 micrometers wavelength were estimated to be (3.2+/- 0.4)*10-19 cm2 and (5.0+/- 0.6)X10-20 cm2, respectively. Results of study absorption and luminescence spectra of different glass ceramics on the base of magnesium-aluminum, zinc-aluminum, lithium-aluminum spinel nanocrystallites doped with tetrahedrally coordinated Co2+ ions are also analyzed.
Phase diagram of two interacting helical states
NASA Astrophysics Data System (ADS)
Santos, Raul A.; Gutman, D. B.; Carr, Sam T.
2016-06-01
We consider two coupled time-reversal-invariant helical edge modes of the same helicity, such as would occur on two stacked quantum spin Hall insulators. In the presence of interaction, the low-energy physics is described by two collective modes, one corresponding to the total current flowing around the edge and the other one describing relative fluctuations between the two edges. We find that quite generically, the relative mode becomes gapped at low temperatures, but only when tunneling between the two helical modes is nonzero. There are two distinct possibilities for the gapped state depending on the relative size of different interactions. If the intraedge interaction is stronger than the interedge interaction, the state is characterized as a spin-nematic phase. However, in the opposite limit, when the interaction between the helical edge modes is strong compared to the interaction within each mode, a spin-density wave forms, with emergent topological properties. First, the gap protects the conducting phase against localization by weak nonmagnetic impurities; second, the protected phase hosts localized zero modes on the ends of the edge that may be created by sufficiently strong nonmagnetic impurities.
Galois algebras of squeezed quantum phase states
NASA Astrophysics Data System (ADS)
Planat, Michel; Saniga, Metod
2005-12-01
Coding, transmission and recovery of quantum states with high security and efficiency, and with as low fluctuations as possible, is the main goal of quantum information protocols and their proper technical implementations. The paper deals with this topic, focusing on the quantum states related to Galois algebras. We first review the constructions of complete sets of mutually unbiased bases in a Hilbert space of dimension q = pm, with p being a prime and m a positive integer, employing the properties of Galois fields Fq (for p>2) and/or Galois rings of characteristic four R4m (for p = 2). We then discuss the Gauss sums and their role in describing quantum phase fluctuations. Finally, we examine an intricate connection between the concepts of mutual unbiasedness and maximal entanglement.
1 Mixing state and absorbing properties of black carbon during Arctic haze
NASA Astrophysics Data System (ADS)
Zanatta, Marco; Gysel, Martin; Eleftheriadis, Kosas; Laj, Paolo; Hans-Werner, Jacobi
2016-04-01
The Arctic atmosphere is periodically affected by the Arctic haze occurring in spring. One of its particulate components is the black carbon (BC), which is considered to be an important contributor to climate change in the Arctic region. Beside BC-cloud interaction and albedo reduction of snow, BC may influence Arctic climate interacting directly with the solar radiation, warming the corresponding aerosol layer (Flanner, 2013). Such warming depends on BC atmospheric burden and also on the efficiency of BC to absorb light, in fact the light absorption is enhanced by mixing of BC with other atmospheric non-absorbing materials (lensing effect) (Bond et al., 2013). The BC reaching the Arctic is evilly processed, due to long range transport. Aging promote internal mixing and thus absorption enhancement. Such modification of mixing and is quantification after long range transport have been observed in the Atlantic ocean (China et al., 2015) but never investigated in the Arctic. During field experiments conducted at the Zeppelin research site in Svalbard during the 2012 Arctic spring, we investigated the relative precision of different BC measuring techniques; a single particle soot photometer was then used to assess the coating of Arctic black carbon. This allowed quantifying the absorption enhancement induced by internal mixing via optical modelling; the optical assessment of aged black carbon in the arctic will be of major interest for future radiative forcing assessment.Optical characterization of the total aerosol indicated that in 2012 no extreme smoke events took place and that the aerosol population was dominated by fine and non-absorbing particles. Low mean concentration of rBC was found (30 ng m-3), with a mean mass equivalent diameter above 200 nm. rBC concentration detected with the continuous soot monitoring system and the single particle soot photometer was agreeing within 15%. Combining absorption coefficient observed with an aethalometer and rBC mass
Harmonic mode locking of bound-state solitons fiber laser based on MoS(2) saturable absorber.
Wang, Yadong; Mao, Dong; Gan, Xuetao; Han, Lei; Ma, Chaojie; Xi, Teli; Zhang, Yi; Shang, Wuyun; Hua, Shijia; Zhao, Jianlin
2015-01-12
We present a kind of harmonic mode locking of bound-state solitons in a fiber laser based on molybdenum disulfide (MoS(2)) saturable absorber (SA). The mode locker is fabricated by depositing MoS(2) nanosheets on a D-shaped fiber (DF). In the fiber laser, two solitons form the bound-state pulses with a temporal separation of 3.4 ps, and the bound-state pulses are equally distributed at a repetition rate of 125 MHz, corresponding to 14th harmonics of fundamental cavity repetition rate (8.968 MHz). Single- and multiple-pulses emissions are also observed by changing the pump power and optimizing the DF based MoS(2) SA. Our experiment demonstrates an interesting operation regime of mode-locked fiber laser, and shows that DF based MoS(2) SA can work as a promising high-power mode locker in ultrafast lasers. PMID:25835667
NASA Astrophysics Data System (ADS)
McMeeking, G. R.; Kreidenweis, S. M.; Yokelson, R. J.; Sullivan, A. P.; Lee, T.; Collett, J. L.; Fortner, E.; Onasch, T. B.; Akagi, S. K.; Taylor, J.; Coe, H.
2012-12-01
Black carbon (BC) aerosol emitted from fires absorbs light, leading to visibility degradation as well as regional and global climate impacts. Fires also emit a wide range of trace gases and particulates that can interact with emitted BC and alter its optical properties and atmospheric lifetime. Non-BC particulate species emitted by fires can also scatter and absorb light, leading to additional effects on visibility. Recent work has shown that certain organic species can absorb light strongly at shorter wavelengths, giving it a brown or yellow color. This material has been classified as brown carbon, though it is not yet well defined. Land managers must find a balance between the negative impacts of prescribed fire emissions on visibility and air quality and the need to prevent future catastrophic wildfire as well as manage ecosystems for habitat restoration or other purposes. This decision process requires accurate assessments of the visibility impacts of fire emissions, including BC and brown carbon, which in turn depend on their optical properties. We present recent laboratory and aircraft measurements of black carbon and aerosol optical properties emitted from biomass burning. All measurement campaigns included a single particle soot photometer (SP2) instrument capable of providing size-resolved measurements of BC mass and number distributions and mixing state, which are needed to separate the BC and brown carbon contributions to total light absorption. The laboratory experiments also included a three-wavelength photoacoustic spectrometer that provided accurate measurements of aerosol light absorption. The laboratory systems also characterized emissions after they had been treated with a thermal denuder to remove semi-volatile coatings, allowing an assessment of the role of non-BC coatings on bulk aerosol optical properties. Emissions were also aged in an environmental smog chamber to examine the role of secondary aerosol production on aerosol optical properties.
Bound-state fiber laser mode-locked by a graphene-nanotube saturable absorber
NASA Astrophysics Data System (ADS)
Yang, H. R.; Chen, G. W.; Kong, Y. C.; Li, W. L.
2015-02-01
We have experimentally observed the multiple bound states in a linear-cavity fiber laser mode-locked by a mixture of graphene and single-walled carbon nanotubes. The proposed laser can deliver the fundamental frequency soliton as well as the two and three bound-state solitons at suitable conditions. The numerical simulations confirm the experimental observations. Both the theoretical predictions and experimental results reveal that the spectral filtering effect plays a key role on the lasers.
Iron Chalcogenide Photovoltaic Absorbers
Yu, Liping; Lany, Stephan; Kykyneshi, Robert; Jieratum, Vorranutch; Ravichandran, Ram; Pelatt, Brian; Altschul, Emmeline; Platt, Heather A. S.; Wager, John F.; Keszler, Douglas A.; Zunger, Alex
2011-08-10
An integrated computational and experimental study of FeS₂ pyrite reveals that phase coexistence is an important factor limiting performance as a thin-film solar absorber. This phase coexistence is suppressed with the ternary materials Fe₂SiS₄ and Fe₂GeS₄, which also exhibit higher band gaps than FeS₂. Thus, the ternaries provide a new entry point for development of thin-film absorbers and high-efficiency photovoltaics.
High-repetition-rate Q-modulation in solid-state laser using fast saturable absorber V:YAG
NASA Astrophysics Data System (ADS)
Ma, Jia-Sai; Wang, Feng; Li, Pei-Xin; Hu, Wei-Wei; Yin, Chun-Hao; Xu, Jin-Long
2015-07-01
A high-repetition-rate Q-modulation operation in a solid-state Nd:GdVO4 laser with a V3+:YAG saturable absorber has been demonstrated in this paper. The V3+:YAG crystal behaves as a fast saturable absorber in this laser because of its very short lifetime of 22 ns. Taking advantage of such fast bleaching recovery and effective cooling of the V:YAG by a home-made copper holder, we realized a pulse repetition rate of 2.4 MHz, which is, to our best knowledge, the maximum among the reported passively Q-switched lasers. The corresponding average output power and pulse width were 1.28 W and 170 ns, respectively, giving a slope efficiency of 15.9% and a pulse energy of 0.53 µJ. This compact high-repetition-rate Q-switched laser offers a potential application in the construction of low-cost, integrated and portable sensing detection equipment which needs a high laser pulse repetition rate.
NASA Astrophysics Data System (ADS)
Ma, Ruixin; Yang, Fan; Li, Shina; Zhang, Xiaoyong; Li, Xiang; Cheng, Shiyao; Liu, Zilin
2016-04-01
CZTSSe is an important earth abundant collection of materials for the development of low cost and high efficiency thin film solar cells. This work developed a simple non-vacuum-based route to fabricate CZTSSe absorber films. This was demonstrated by first synthesizing Cu2ZnSnS4 (CZTS) nano-crystalline based on solid-phase synthesis. Then a stable colloidal ink composed of CZTS nano-crystalline was blade coated on Mo-coated substrates followed by an annealing process under Ar atmosphere. After CZTS films formation, the films were sintered into CZTSSe absorber films by exposing them under Selenium vapor. The formation of a kesterite type CZTS was confirmed using X-ray diffraction and Raman scattering measurements. The band gap of CZTSSe absorber films was determined to be 1.26 eV, which was appropriate for use as an absorber layer in thin film solar cells. The CZTSSe absorber films showed a good photovoltatic performance, demonstrating this simple approach had great potential for CZTSSe solar cell production.
Zhao, Yongguang; Li, Xianlei; Xu, Miaomiao; Yu, Haohai; Wu, Yongzhong; Wang, Zhengping; Hao, Xiaopeng; Xu, Xinguang
2013-02-11
Using multilayered graphene as the saturable absorber (SA), Nd:LYSO crystal as the laser material, we demonstrated a laser-diode (LD) pumped, dual-wavelength passively Q-switched solid-state laser. The maximum average output power is 1.8 W, the largest pulse energy and highest peak power is 11.3 μJ, 118 W, respectively. As we have known, they are the best results for passively Q-switched operation of graphene. The pulse laser is strong enough to realize extra-cavity frequency conversions. With a KTP crystal as the sum-frequency generator, the dual wavelengths are proved to be well time overlapped, which manifests the synchronous modulation to the dual-wavelength with multi-layered graphene. PMID:23481809
Equations of State and Phase Diagrams of Ammonia
ERIC Educational Resources Information Center
Glasser, Leslie
2009-01-01
We present equations of state relating the phases and a three-dimensional phase diagram for ammonia with its solid, liquid, and vapor phases, based on fitted authentic experimental data and including recent information on the high-pressure solid phases. This presentation follows similar articles on carbon dioxide and water published in this…
NASA Astrophysics Data System (ADS)
Meadows, H. J.; Bhatia, A.; Stefan, C.; Schorr, S.; Scarpulla, M. A.; Dale, P. J.
2013-09-01
For the production of high efficiency thin film, Cu(In,Ga)Se2 solar cells, absorber layers with grain sizes of a few hundred nanometers and without detrimental secondary phases are favored. Co-electrodeposition offers a low-cost and material efficient synthesis route, where, in a single step, films containing CuInSe2 are formed. However, the material is nanocrystalline, constitutes multiple phases and has poor photovoltaic properties 1. Therefore a subsequent annealing step is required to produce absorber layers suitable for use in photovoltaic devices. Laser annealing has been demonstrated to improve crystallinity, stimulate atomic diffusion and develop opto-electronic properties when compared to the precursor 2. In this work, high resolution X-ray diffraction was used in order to assess the presence of secondary phases in the absorber layer. All diffractograms of laser annealed films exhibited an additional, unknown peak, measurable through the full depth of the material which is independent of precursor composition, annealing time or laser flux. Evaluation of literature on codeposited CuInSe2, combined with Rietveld refinement suggests a number of possible identities for this peak. The candidates in order of most likely to least likely are structural defects, In2Se3, and CuIn3Se5. We consider the impact that each of these would have on a device formed via this process and thus its success as a new manufacturing route for CuInSe2 solar cells.
NASA Astrophysics Data System (ADS)
Gradišek, A.; Kocjan, A.; McGuiness, P. J.; Apih, T.; Kim, Hae Jin; Dolinšek, J.
2008-11-01
The Ti40Zr40Ni20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.
Phase properties of multicomponent superposition states in various amplifiers
NASA Technical Reports Server (NTRS)
Lee, Kang-Soo; Kim, M. S.
1994-01-01
There have been theoretical studies for generation of optical coherent superposition states. Once the superposition state is generated it is natural to ask if it is possible to amplify it without losing the nonclassical properties of the field state. We consider amplification of the superposition state in various amplifiers such as a sub-Poissonian amplifier, a phase-sensitive amplifier and a classical amplifier. We show the evolution of phase probability distribution functions in the amplifier.
Features of the extreme events observed in an all-solid-state laser with a saturable absorber
NASA Astrophysics Data System (ADS)
Bonazzola, Carlos R.; Hnilo, Alejandro A.; Kovalsky, Marcelo G.; Tredicce, Jorge R.
2015-11-01
Extreme events in the form of pulses of extraordinary intensity (sometimes also called optical rogue waves) are easily observed in the chaotic regime of an all-solid-state laser with a saturable absorber if the Fresnel number of the cavity is high. This result suggests that the nonlinear interaction among transverse modes is an essential ingredient in the formation of extreme events in this type of laser, but there is no theoretical description of the phenomenon yet. We report here a set of experimental results on the regularities of these extreme events in order to provide a basis for the development of such a description. Among these results, we point out here (i) the decay of the correlation across the transversal section of the laser beam, and (ii) the appearance of extreme events even if the time elapsed since the previous pulse is relatively short (in terms of the average interpulse time interval), which indicates the existence of some unknown mechanism of energy storage. We hypothesize that this mechanism is related to the imperfect depletion of the gain by some of the transversal modes. We also present evidence in support of this hypothesis.
Geometric Phase for Adiabatic Evolutions of General Quantum States
Wu, Biao; Liu, Jie; Niu, Qian; Singh, David J
2005-01-01
The concept of a geometric phase (Berry's phase) is generalized to the case of noneigenstates, which is applicable to both linear and nonlinear quantum systems. This is particularly important to nonlinear quantum systems, where, due to the lack of the superposition principle, the adiabatic evolution of a general state cannot be described in terms of eigenstates. For linear quantum systems, our new geometric phase reduces to a statistical average of Berry's phases. Our results are demonstrated with a nonlinear two-level model.
Geometric phases for mixed states of the Kitaev chain.
Andersson, Ole; Bengtsson, Ingemar; Ericsson, Marie; Sjöqvist, Erik
2016-05-28
The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyse the intricate behaviour of Uhlmann's geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyse the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation. PMID:27091168
Maitra, Dipankar; Miller, Jon M. E-mail: jonmm@umich.ed
2010-07-20
A recent observation of the nearby (z = 0.042) narrow-line Seyfert 1 galaxy RE J1034+396 on 2007 May 31 showed strong quasi-periodic oscillations (QPOs) in the 0.3-10 keV X-ray flux. We present phase-resolved spectroscopy of this observation, using data obtained by the EPIC PN detector on board XMM-Newton. The 'low' phase spectrum, associated with the troughs in the light curve, shows (at >4{sigma} confidence level) an absorption edge at 0.86 {+-} 0.05 keV with an absorption depth of 0.3 {+-} 0.1. Ionized oxygen edges are hallmarks of X-ray warm absorbers in Seyfert active galactic nuclei; the observed edge is consistent with H-like O VIII and implies a column density of N{sub OVIII} {approx} 3 x 10{sup 18} cm{sup -2}. The edge is not seen in the 'high' phase spectrum associated with the crests in the light curve, suggesting the presence of a warm absorber in the immediate vicinity of the supermassive black hole that periodically obscures the continuum emission. If the QPO arises due to Keplerian orbital motion around the central black hole, the periodic appearance of the O VIII edge would imply a radius of {approx}9.4(M/[4x10{sup 6}M{sub sun}]){sup -2/3}(P/[1 hr]){sup 2/3} r{sub g} for the size of the warm absorber.
Phase space flow of particles in squeezed states
NASA Technical Reports Server (NTRS)
Ceperley, Peter H.
1994-01-01
The manipulation of noise and uncertainty in squeezed states is governed by the wave nature of the quantum mechanical particles in these states. This paper uses a deterministic model of quantum mechanics in which real guiding waves control the flow of localized particles. This model will be used to examine the phase space flow of particles in typical squeezed states.
NASA Astrophysics Data System (ADS)
Fuchs, H. V.; Möser, M.
Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.
Equations of state and phase diagrams of hydrogen isotopes
Urlin, V. D.
2013-11-15
A new form of the semiempirical equation of state proposed for the liquid phase of hydrogen isotopes is based on the assumption that its structure is formed by cells some of which contain hydrogen molecules and others contain hydrogen atoms. The values of parameters in the equations of state of the solid (molecular and atomic) phases as well as of the liquid phase of hydrogen isotopes (protium and deuterium) are determined. Phase diagrams, shock adiabats, isentropes, isotherms, and the electrical conductivity of compressed hydrogen are calculated. Comparison of the results of calculations with available experimental data in a wide pressure range demonstrates satisfactory coincidence.
NASA Astrophysics Data System (ADS)
Schaeck, S.; Stoermer, A. O.; Hockgeiger, E.
The BMW Group has launched two micro-hybrid functions in high volume models in order to contribute to reduction of fuel consumption in modern passenger cars. Both the brake energy regeneration (BER) and the auto-start-stop function (ASSF) are based on the conventional 14 V vehicle electrical system and current series components with only little modifications. An intelligent control algorithm of the alternator enables recuperative charging in braking and coasting phases, known as BER. By switching off the internal combustion engine at a vehicle standstill the idling fuel consumption is effectively reduced by ASSF. By reason of economy and package a lead-acid battery is used as electrochemical energy storage device. The BMW Group assembles valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology in the micro-hybrid electrical power system since special challenges arise for the batteries. By field data analysis a lower average state-of-charge (SOC) due to partial state-of-charge (PSOC) operation and a higher cycling rate due to BER and ASSF are confirmed in this article. Similar to a design of experiment (DOE) like method we present a long-term lab investigation. Two types of 90 Ah VRLA AGM batteries are operated with a test bench profile that simulates the micro-hybrid vehicle electrical system under varying conditions. The main attention of this lab testing is focused on capacity loss and charge acceptance over cycle life. These effects are put into context with periodically refresh charging the batteries in order to prevent accelerated battery aging due to hard sulfation. We demonstrate the positive effect of refresh chargings concerning preservation of battery charge acceptance. Furthermore, we observe moderate capacity loss over 90 full cycles both at 25 °C and at 3 °C battery temperature.
Gaussian cloning of coherent states with known phases
Alexanian, Moorad
2006-04-15
The fidelity for cloning coherent states is improved over that provided by optimal Gaussian and non-Gaussian cloners for the subset of coherent states that are prepared with known phases. Gaussian quantum cloning duplicates all coherent states with an optimal fidelity of 2/3. Non-Gaussian cloners give optimal single-clone fidelity for a symmetric 1-to-2 cloner of 0.6826. Coherent states that have known phases can be cloned with a fidelity of 4/5. The latter is realized by a combination of two beam splitters and a four-wave mixer operated in the nonlinear regime, all of which are realized by interaction Hamiltonians that are quadratic in the photon operators. Therefore, the known Gaussian devices for cloning coherent states are extended when cloning coherent states with known phases by considering a nonbalanced beam splitter at the input side of the amplifier.
Bubis, E L
2011-06-30
Self-imaging of transparent objects and structures in focusing of a spatially phase-modulated laser beam into an extended weakly absorbing medium is described. The laser power level that is necessary for effective imaging corresponds to the illuminating beam power when thermal self-defocusing starts evolving in the medium. The effect can be described in terms of the ideology of Zernike's classical phase-contrast method. Edge enhancement in visualised images of transparent objects is experimentally demonstrated. Self-imaging of a microscopic object in the form of transparent letters and long-lived refractive-index fluctuations in liquid glycerol is shown. Due to the adaptivity of the process under consideration, unlike the classical case, self-imaging occurs also in the situations where a beam is displaced (undergoes random walk) as a whole in the Fourier plane, for example, in the presence of thermal flows. (image processing)
NASA Astrophysics Data System (ADS)
Schneider, P. C.; France, K.; Günther, H. M.; Herczeg, G.; Robrade, J.; Bouvier, J.; McJunkin, M.; Schmitt, J. H. M. M.
2015-12-01
AA Tau is a well-studied, nearby classical T Tauri star, which is viewed almost edge-on. A warp in its inner disk periodically eclipses the central star, causing a clear modulation of its optical light curve. The system underwent a major dimming event beginning in 2011 caused by an extra absorber, which is most likely associated with additional disk material in the line of sight toward the central source. We present new XMM-Newton X-ray, Hubble Space Telescope FUV, and ground-based optical and near-infrared data of the system obtained in 2013 during the long-lasting dim phase. The line width decrease of the fluorescent H2 disk emission shows that the extra absorber is located at r > 1 au. Comparison of X-ray absorption (NH) with dust extinction (AV), as derived from measurements obtained one inner disk orbit (eight days) after the X-ray measurement, indicates that the gas-to-dust ratio as probed by the NH to AV ratio of the extra absorber is compatible with the ISM ratio. Combining both results suggests that the extra absorber, i.e., material at r > 1 au, has no significant gas excess in contrast to the elevated gas-to-dust ratio previously derived for material in the inner region (≲0.1 au). Appendices are available in electronic form at http://www.aanda.org
NASA Astrophysics Data System (ADS)
Li, Xiaohui; Wu, Kan; Sun, Zhipei; Meng, Bo; Wang, Yonggang; Wang, Yishan; Yu, Xuechao; Yu, Xia; Zhang, Ying; Shum, Perry Ping; Wang, Qi Jie
2016-04-01
Low phase noise mode-locked fiber laser finds important applications in telecommunication, ultrafast sciences, material science, and biology, etc. In this paper, two types of carbon nano-materials, i.e. single-wall carbon nanotube (SWNT) and graphene oxide (GO), are investigated as efficient saturable absorbers (SAs) to achieve low phase noise mode-locked fiber lasers. Various properties of these wall-paper SAs, such as saturable intensity, optical absorption and degree of purity, are found to be key factors determining the performance of the ultrafast pulses. Reduced-noise femtosecond fiber lasers based on such carbon-based SAs are experimentally demonstrated, for which the phase noise has been reduced by more than 10 dB for SWNT SAs and 8 dB for GO SAs at 10 kHz. To the best of our knowledge, this is the first investigation on the relationship between different carbon material based SAs and the phase noise of mode-locked lasers. This work paves the way to generate high-quality low phase noise ultrashort pulses in passively mode-locked fiber lasers.
Li, Xiaohui; Wu, Kan; Sun, Zhipei; Meng, Bo; Wang, Yonggang; Wang, Yishan; Yu, Xuechao; Yu, Xia; Zhang, Ying; Shum, Perry Ping; Wang, Qi Jie
2016-01-01
Low phase noise mode-locked fiber laser finds important applications in telecommunication, ultrafast sciences, material science, and biology, etc. In this paper, two types of carbon nano-materials, i.e. single-wall carbon nanotube (SWNT) and graphene oxide (GO), are investigated as efficient saturable absorbers (SAs) to achieve low phase noise mode-locked fiber lasers. Various properties of these wall-paper SAs, such as saturable intensity, optical absorption and degree of purity, are found to be key factors determining the performance of the ultrafast pulses. Reduced-noise femtosecond fiber lasers based on such carbon-based SAs are experimentally demonstrated, for which the phase noise has been reduced by more than 10 dB for SWNT SAs and 8 dB for GO SAs at 10 kHz. To the best of our knowledge, this is the first investigation on the relationship between different carbon material based SAs and the phase noise of mode-locked lasers. This work paves the way to generate high-quality low phase noise ultrashort pulses in passively mode-locked fiber lasers. PMID:27126900
Li, Xiaohui; Wu, Kan; Sun, Zhipei; Meng, Bo; Wang, Yonggang; Wang, Yishan; Yu, Xuechao; Yu, Xia; Zhang, Ying; Shum, Perry Ping; Wang, Qi Jie
2016-01-01
Low phase noise mode-locked fiber laser finds important applications in telecommunication, ultrafast sciences, material science, and biology, etc. In this paper, two types of carbon nano-materials, i.e. single-wall carbon nanotube (SWNT) and graphene oxide (GO), are investigated as efficient saturable absorbers (SAs) to achieve low phase noise mode-locked fiber lasers. Various properties of these wall-paper SAs, such as saturable intensity, optical absorption and degree of purity, are found to be key factors determining the performance of the ultrafast pulses. Reduced-noise femtosecond fiber lasers based on such carbon-based SAs are experimentally demonstrated, for which the phase noise has been reduced by more than 10 dB for SWNT SAs and 8 dB for GO SAs at 10 kHz. To the best of our knowledge, this is the first investigation on the relationship between different carbon material based SAs and the phase noise of mode-locked lasers. This work paves the way to generate high-quality low phase noise ultrashort pulses in passively mode-locked fiber lasers. PMID:27126900
Solid state phase detector replaces bulky transformer circuit
NASA Technical Reports Server (NTRS)
Moberly, C. L.
1967-01-01
Miniature solid state phase detector using MOSFETs is used in a phase lock loop with a sun-bit detector in an integrated data-link circuit. This replaces bulky transformer circuits. It uses an inverter amplifier, a modulator switch, and a buffer amplifier.
Quantum phase estimation using path-symmetric entangled states
Lee, Su-Yong; Lee, Chang-Woo; Lee, Jaehak; Nha, Hyunchul
2016-01-01
We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |φ〉|0〉 + |0〉|φ〉, where an arbitrary state |φ〉 occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state |φ〉. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state |φ〉. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2π] of unknown phase shift ϕ whereas a parity measurement does so in a certain confined range of ϕ. By introducing a component state of the form , we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy Nav > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation. PMID:27457267
Quantum phase estimation using path-symmetric entangled states
NASA Astrophysics Data System (ADS)
Lee, Su-Yong; Lee, Chang-Woo; Lee, Jaehak; Nha, Hyunchul
2016-07-01
We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |φ>|0> + |0>|φ>, where an arbitrary state |φ> occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state |φ>. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state |φ>. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2π] of unknown phase shift ϕ whereas a parity measurement does so in a certain confined range of ϕ. By introducing a component state of the form , we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy Nav > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation.
Quantum phase estimation using path-symmetric entangled states.
Lee, Su-Yong; Lee, Chang-Woo; Lee, Jaehak; Nha, Hyunchul
2016-01-01
We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |φ〉|0〉 + |0〉|φ〉, where an arbitrary state |φ〉 occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state |φ〉. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state |φ〉. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2π] of unknown phase shift ϕ whereas a parity measurement does so in a certain confined range of ϕ. By introducing a component state of the form , we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy Nav > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation. PMID:27457267
Wang, Jianling; Xiao, Xiaofeng; Chen, Tong; Liu, Tingfei; Tao, Huaming; He, Jun
2016-06-17
The glyceride in oil food simulant usually causes serious interferences to target analytes and leads to failure of the normal function of the RP-HPLC column. In this work, a convenient HPLC-UV method for the determination of the total specific migration of nine ultraviolet (UV) absorbers in food simulants was developed based on 1,1,3,3-tetramethylguanidine (TMG) and organic phase anion exchange (OPAE) SPE to efficiently remove glyceride in olive oil simulant. In contrast to the normal ion exchange carried out in an aqueous solution or aqueous phase environment, the OPAE SPE was performed in the organic phase environments, and the time-consuming and challenging extraction of the nine UV absorbers from vegetable oil with aqueous solution could be readily omitted. The method was proved to have good linearity (r≥0.99992), precision (intra-day RSD≤3.3%), and accuracy(91.0%≤recoveries≤107%); furthermore, the lower limit of quantifications (0.05-0.2mg/kg) in five types of food simulants(10% ethanol, 3% acetic acid, 20% ethanol, 50% ethanol and olive oil) was observed. The method was found to be well suited for quantitative determination of the total specific migration of the nine UV absorbers both in aqueous and vegetable oil simulant according to Commission Regulation (EU) No. 10/2011. Migration levels of the nine UV absorbers were determined in 31 plastic samples, and UV-24, UV-531, HHBP and UV-326 were frequently detected, especially in olive oil simulant for UV-326 in PE samples. In addition, the OPAE SPE procedure was also been applied to efficiently enrich or purify seven antioxidants in olive oil simulant. Results indicate that this procedure will have more extensive applications in the enriching or purification of the extremely weak acidic compounds with phenol hydroxyl group that are relatively stable in TMG n-hexane solution and that can be barely extracted from vegetable oil. PMID:27189432
Solid state photomultiplier for astronomy, phase 2
NASA Technical Reports Server (NTRS)
Besser, P. J.; Hays, K. M.; Laviolette, R. A.
1989-01-01
Epitaxial layers with varying donor concentration profiles were grown on silicon substrate wafers using chemical vapor deposition (CVD) techniques, and solid state photomultiplier (SSPM) devices were fabricated from the wafers. Representative detectors were tested in a low background photon flux, low temperature environment to determine the device characteristics for comparison to NASA goals for astronomical applications. The SSPM temperatures varied between 6 and 11 K with background fluxes in the range from less than 5 x 10 to the 6th power to 10 to the 13th power photons/square cm per second at wavelengths of 3.2 and 20 cm. Measured parameters included quantum efficiency, dark count rate and bias current. Temperature for optimal performance is 10 K, the highest ever obtained for SSPMs. The devices exhibit a combination of the lowest dark current and highest quantum efficiency yet achieved. Experimental data were reduced, analyzed and used to generate recommendations for future studies. The background and present status of the microscopic theory of SSPM operation were reviewed and summarized. Present emphasis is on modeling of the avalanche process which is the basis for SSPM operation. Approaches to the solution of the Boltzmann transport equation are described and the treatment of electron scattering mechanisms is presented. The microscopic single-electron transport theory is ready to be implemented for large-scale computations.
Roppo, V.; Cojocaru, C.; Trull, J.; Vilaseca, R.; Raineri, F.; Halioua, Y.; Raj, R.; Sagnes, I.; D'Aguanno, G.; Scalora, M.
2009-10-15
We predict and experimentally observe the enhancement by three orders of magnitude of phase mismatched second and third harmonic generation in a GaAs cavity at 650 and 433 nm, respectively, well above the absorption edge. Phase locking between the pump and the harmonics changes the effective dispersion of the medium and inhibits absorption. Despite hostile conditions the harmonics resonate inside the cavity and become amplified leading to relatively large conversion efficiencies. Field localization thus plays a pivotal role despite the presence of absorption, and ushers in a new class of semiconductor-based devices in the visible and uv ranges.
NASA Astrophysics Data System (ADS)
Meiser, J.; Amberger, M.; Willner, M.; Kunka, D.; Meyer, P.; Koch, F.; Hipp, A.; Walter, M.; Pfeiffer, F.; Mohr, J.
2014-03-01
X-ray phase contrast imaging has become a promising biomedical imaging technique for enhancing soft-tissue contrast. In addition to an absorption contrast image it provides two more types of image, a phase contrast and a small-angle scattering contrast image recorded at the same time. In biomedical imaging their combination allows for the conventional investigation of e.g. bone fractures on the one hand and for soft-tissue investigation like cancer detection on the other hand. Among the different methods of X-ray phase contrast imaging the grating based approach, the Talbot-Lau interferometry, has the highest potential for commercial use in biomedical imaging at the moment, because commercially available X-ray sources can be used in a compact setup. In Talbot-Lau interferometers, core elements are phase and absorption gratings with challenging specifications because of their high aspect ratios (structure height over width). For the long grating lamellas structural heights of more than 100 μm together with structural width in the micron range are requested. We are developing a fabrication process based on deep x-ray lithography and electroforming (LIGA) to fabricate these challenging structures. In case of LIGA gratings the structural area is currently limited to several centimeters by several centimeters which limit the field of view in grating based X-ray phase contrast imaging. In order to increase the grating area significantly we are developing a stitching method for gratings using a 625 μm thick silicon wafer as a carrier substrate. In this work we compare the silicon carrier with an alternative one, polyimide, for patient dose reduction and for the use at lower energies in terms of transmission and image reconstruction problems.
Edge states and phase diagram for graphene under polarized light
Wang, Yi -Xiang; Li, Fuxiang
2016-03-22
In this paper, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, themore » number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.« less
Edge states and phase diagram for graphene under polarized light
NASA Astrophysics Data System (ADS)
Wang, Yi-Xiang; Li, Fuxiang
2016-07-01
In this work, we investigate the topological phase transitions in graphene under the modulation of circularly polarized light, by analyzing the changes of edge states and its topological structures. A full phase diagram, with several different topological phases, is presented in the parameter space spanned by the driving frequency and light strength. We find that the high-Chern number behavior is very common in the driven system. While the one-photon resonance can create the chiral edge states in the π-gap, the two-photon resonance will induce the counter-propagating edge modes in the zero-energy gap. When the driving light strength is strong, the number and even the chirality of the edge states may change in the π-gap. The robustness of the edge states to disorder potential is also examined. We close by discussing the feasibility of experimental proposals.
Persistent chimera states in nonlocally coupled phase oscillators
NASA Astrophysics Data System (ADS)
Suda, Yusuke; Okuda, Koji
2015-12-01
Chimera states in the systems of nonlocally coupled phase oscillators are considered stable in the continuous limit of spatially distributed oscillators. However, it is reported that in the numerical simulations without taking such limit, chimera states are chaotic transient and finally collapse into the completely synchronous solution. In this Rapid Communication, we numerically study chimera states by using the coupling function different from the previous studies and obtain the result that chimera states can be stable even without taking the continuous limit, which we call the persistent chimera state.
Unidirectional perfect absorber.
Jin, L; Wang, P; Song, Z
2016-01-01
This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125
Cavity State Manipulation Using Photon-Number Selective Phase Gates
NASA Astrophysics Data System (ADS)
Heeres, Reinier W.; Vlastakis, Brian; Holland, Eric; Krastanov, Stefan; Albert, Victor V.; Frunzio, Luigi; Jiang, Liang; Schoelkopf, Robert J.
2015-09-01
The large available Hilbert space and high coherence of cavity resonators make these systems an interesting resource for storing encoded quantum bits. To perform a quantum gate on this encoded information, however, complex nonlinear operations must be applied to the many levels of the oscillator simultaneously. In this work, we introduce the selective number-dependent arbitrary phase (snap) gate, which imparts a different phase to each Fock-state component using an off-resonantly coupled qubit. We show that the snap gate allows control over the quantum phases by correcting the unwanted phase evolution due to the Kerr effect. Furthermore, by combining the snap gate with oscillator displacements, we create a one-photon Fock state with high fidelity. Using just these two controls, one can construct arbitrary unitary operations, offering a scalable route to performing logical manipulations on oscillator-encoded qubits.
Regional Patterns of Cortical Phase Synchrony in the Resting State.
Casimo, Kaitlyn; Darvas, Felix; Wander, Jeremiah; Ko, Andrew; Grabowski, Thomas J; Novotny, Edward; Poliakov, Andrew; Ojemann, Jeffrey G; Weaver, Kurt E
2016-07-01
Synchronized phase estimates between oscillating neuronal signals at the macroscale level reflect coordinated activities between neuronal assemblies. Recent electrophysiological evidence suggests the presence of significant spontaneous phase synchrony within the resting state. The purpose of this study was to investigate phase synchrony, including directional interactions, in resting state subdural electrocorticographic recordings to better characterize patterns of regional phase interactions across the lateral cortical surface during the resting state. We estimated spontaneous phase locking value (PLV) as a measure of functional connectivity, and phase slope index (PSI) as a measure of pseudo-causal phase interactions, across a broad range of canonical frequency bands and the modulation of the amplitude envelope of high gamma (amHG), a band that is believed to best reflect the physiological processes giving rise to the functional magnetic resonance imaging BOLD signal. Long-distance interactions had higher PLVs in slower frequencies (≤theta) than in higher ones (≥beta) with amHG behaving more like slow frequencies, and a general trend of increasing frequency band of significant PLVs when moving across the lateral surface along an anterior-posterior axis. Moreover, there was a strong trend of frontal-to-parietal directional phase synchronization, measured by PSI across multiple frequencies. These findings, which are likely indicative of coordinated and structured spontaneous cortical interactions, are important in the study of time scales and directional nature of resting state functional connectivity, and may ultimately contribute to a better understanding of how spontaneous synchrony is linked to variation in regional architecture across the lateral cortical surface. PMID:27019319
Universal weighted graph state generation with the cross phase modulation
NASA Astrophysics Data System (ADS)
Hu, Jie Ru; Lin, Qing
2016-05-01
We introduce an architecture of cascade CZθ operation for conveniently generating universal weighted graph state. The entanglement bonds between dependent or independent single photons can be created efficiently with only one ancilla single photon. The generation is scalable for universal weighted graph states, including arbitrary two-dimensional or three-dimensional weighted graph states. Moreover, the generation is flexible, including that the controlled phase shift θ between each pair of single photons can be different, the traces of the ancilla single photon walking is not fixed, and the prior entangled states are not required.
Efficient computations of quantum canonical Gibbs state in phase space
NASA Astrophysics Data System (ADS)
Bondar, Denys I.; Campos, Andre G.; Cabrera, Renan; Rabitz, Herschel A.
2016-06-01
The Gibbs canonical state, as a maximum entropy density matrix, represents a quantum system in equilibrium with a thermostat. This state plays an essential role in thermodynamics and serves as the initial condition for nonequilibrium dynamical simulations. We solve a long standing problem for computing the Gibbs state Wigner function with nearly machine accuracy by solving the Bloch equation directly in the phase space. Furthermore, the algorithms are provided yielding high quality Wigner distributions for pure stationary states as well as for Thomas-Fermi and Bose-Einstein distributions. The developed numerical methods furnish a long-sought efficient computation framework for nonequilibrium quantum simulations directly in the Wigner representation.
State-of-the-art review of phase equilibria
Prausnitz, J.M.
1980-03-01
High-pressure phase-equilibrium calculations using an equation of state are more sensitive to the mixing rules than to details in the effect of density or temperature on pressure. Attention must be given to the problem of how to extend equations of state to mixtures. One possible technique is provided by perturbation theory; another by superposition of chemical equilibria. At low or moderate pressures, vapor-phase corrections are often important. When specific intermolecular forces produce formation of molecular aggregates, strong deviations from ideal-gas behavior can be significant even at pressures well below 1 bar. When vapor-liquid equilibrium data are reduced using conventional expressions for the excess Gibbs energy, the resulting binary parameters tend to be partially correlated, it difficult, but no impossible, to calculate ternary liquid-liquid equilibria using binary parameters only. New models for calculating properties of liquid-phase mixtures mist allow for changes in free volume to give consideration to the effect of mixing on changes in rotational and vibrational degrees of freedom. Liquid-phase volumetric effects are also important in describing the solubilities of gases in solvent mixtures. Therefore, future liquid-phase models should incorporate a liquid-phase equation of state, either of the van der Waals type or, perhaps, as given by the direct-correlation function theory of liquids.
Emerging single-phase state in small manganite nanodisks.
Shao, Jian; Liu, Hao; Zhang, Kai; Yu, Yang; Yu, Weichao; Lin, Hanxuan; Niu, Jiebin; Du, Kai; Kou, Yunfang; Wei, Wengang; Lan, Fanli; Zhu, Yinyan; Wang, Wenbin; Xiao, Jiang; Yin, Lifeng; Plummer, E W; Shen, Jian
2016-08-16
In complex oxides systems such as manganites, electronic phase separation (EPS), a consequence of strong electronic correlations, dictates the exotic electrical and magnetic properties of these materials. A fundamental yet unresolved issue is how EPS responds to spatial confinement; will EPS just scale with size of an object, or will the one of the phases be pinned? Understanding this behavior is critical for future oxides electronics and spintronics because scaling down of the system is unavoidable for these applications. In this work, we use La0.325Pr0.3Ca0.375MnO3 (LPCMO) single crystalline disks to study the effect of spatial confinement on EPS. The EPS state featuring coexistence of ferromagnetic metallic and charge order insulating phases appears to be the low-temperature ground state in bulk, thin films, and large disks, a previously unidentified ground state (i.e., a single ferromagnetic phase state emerges in smaller disks). The critical size is between 500 nm and 800 nm, which is similar to the characteristic length scale of EPS in the LPCMO system. The ability to create a pure ferromagnetic phase in manganite nanodisks is highly desirable for spintronic applications. PMID:27482108
Emerging single-phase state in small manganite nanodisks
Shao, Jian; Liu, Hao; Zhang, Kai; Yu, Yang; Yu, Weichao; Lin, Hanxuan; Niu, Jiebin; Du, Kai; Kou, Yunfang; Wei, Wengang; Lan, Fanli; Zhu, Yinyan; Wang, Wenbin; Xiao, Jiang; Yin, Lifeng; Plummer, E. W.; Shen, Jian
2016-01-01
In complex oxides systems such as manganites, electronic phase separation (EPS), a consequence of strong electronic correlations, dictates the exotic electrical and magnetic properties of these materials. A fundamental yet unresolved issue is how EPS responds to spatial confinement; will EPS just scale with size of an object, or will the one of the phases be pinned? Understanding this behavior is critical for future oxides electronics and spintronics because scaling down of the system is unavoidable for these applications. In this work, we use La0.325Pr0.3Ca0.375MnO3 (LPCMO) single crystalline disks to study the effect of spatial confinement on EPS. The EPS state featuring coexistence of ferromagnetic metallic and charge order insulating phases appears to be the low-temperature ground state in bulk, thin films, and large disks, a previously unidentified ground state (i.e., a single ferromagnetic phase state emerges in smaller disks). The critical size is between 500 nm and 800 nm, which is similar to the characteristic length scale of EPS in the LPCMO system. The ability to create a pure ferromagnetic phase in manganite nanodisks is highly desirable for spintronic applications. PMID:27482108
Doorway states in the random-phase approximation
De Pace, A.; Molinari, A.; Weidenmüller, H.A.
2014-12-15
By coupling a doorway state to a sea of random background states, we develop the theory of doorway states in the framework of the random-phase approximation (RPA). Because of the symmetry of the RPA equations, that theory is radically different from the standard description of doorway states in the shell model. We derive the Pastur equation in the limit of large matrix dimension and show that the results agree with those of matrix diagonalization in large spaces. The complexity of the Pastur equation does not allow for an analytical approach that would approximately describe the doorway state. Our numerical results display unexpected features: The coupling of the doorway state with states of opposite energy leads to strong mutual attraction.
Accelerated Superposition State Molecular Dynamics for Condensed Phase Systems.
Ceotto, Michele; Ayton, Gary S; Voth, Gregory A
2008-04-01
An extension of superposition state molecular dynamics (SSMD) [Venkatnathan and Voth J. Chem. Theory Comput. 2005, 1, 36] is presented with the goal to accelerate timescales and enable the study of "long-time" phenomena for condensed phase systems. It does not require any a priori knowledge about final and transition state configurations, or specific topologies. The system is induced to explore new configurations by virtue of a fictitious (free-particle-like) accelerating potential. The acceleration method can be applied to all degrees of freedom in the system and can be applied to condensed phases and fluids. PMID:26620930
Ying, Rongjian
2015-01-01
A kind of Sr2+ selective resin was applied as an absorption phase to extract Sr2+ ion from an aqueous solution, and the amount of Sr2+ was determined using inductively coupled plasma optical emission spectrometer. Factors, including absorption time, temperature, stirring rate, salt-out effect, desorption, and the pH of the aqueous solution, were investigated to optimize the absorption efficiency of Sr2+. Foreign ions were examined to observe their effects on the absorption behavior of Sr2+. The optimum condition was absorption time at 20 min, pH of aqueous solution 7, temperature of 35°C, and 600 rpm stirring rate. A 10 mL solution of 0.1 mol/L HCl is used as the desorption agent. The linear range of Sr2+ concentrations from 50 to 1200 μg/L was investigated with the slope of 183 μg/L. The limit of detection was 21 μg/L with 4.23% relative standard deviation. The correlation coefficient was found to be 0.9947. Under the optimized conditions, the concentrations of Sr2+ in four water samples were detected by the developed method. We propose that this method effectively extracts strontium ion from environmental water samples. PMID:26640489
Ouyang, Bing Xue, Jia-Dan Zheng, Xuming E-mail: zxm@zstu.edu.cn; Fang, Wei-Hai E-mail: fangwh@dnu.edu.cn
2014-05-21
The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were very different. The conical intersection point CI(S{sub 2}/S{sub 1}) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S{sub 2}(A′) state: the radiative S{sub 2,min} → S{sub 0} transition and the nonradiative S{sub 2} → S{sub 1} internal conversion via CI(S{sub 2}/S{sub 1}). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S{sub 1}/T{sub 1}) in the excited state decay dynamics of PITC is evaluated.
Hydrogen bond symmetrization and equation of state of phase D
Hushur, Anwar; Manghnani, Murli H.; Smyth, Joseph R.; Williams, Quentin; Hellebrand, Eric; Lonappan, Dayana; Ye, Yu; Dera, Przemyslaw; Frost, Daniel J.
2012-10-09
We have synthesized phase D at 24 GPa and at temperatures of 1250-1100 C in a multianvil press under conditions of high silica activity. The compressibility of this high-silica-activity phase D (Mg{sub 1.0}Si{sub 1.7}H{sub 3.0}O{sub 6}) has been measured up to 55.8 GPa at ambient temperature by powder X-ray diffraction. The volume (V) decreases smoothly with increasing pressure up to 40 GPa, consistent with the results reported in earlier studies. However, a kink is observed in the trend of V versus pressure above {approx}40 GPa, reflecting a change in the compression behavior. The data to 30 GPa fit well to a third-order Birch-Murnaghan equation of state (EoS), yielding V{sub o} = 85.1 {+-} 0.2 {angstrom}{sup 3}; K{sub o} = 167.9 {+-} 8.6 GPa; and K{prime}{sub o} = 4.3 {+-} 0.5, similar to results for Fe-Al-free phase D reported by Frost and Fei (1999). However, these parameters are larger than those reported for Fe-Al-bearing phase D and for Fe-Al-free phase D. The abnormal volume change in this study may be attributed to the reported hydrogen bond symmetrization in phase D. Fitting a third-order Birch-Murnaghan EoS to the data below 30 GPa yields a bulk modulus K{sub o} = 173 (2) GPa for the hydrogen-off-centered (HOC) phase and K{sub o} = 212 (15) GPa for the data above 40 GPa for the hydrogen-centered (HC) phase, assuming K{prime}{sub o} is 4. The calculated bulk modulus K{sub o} of the HC phase is 18% larger than the bulk modulus K{sub o} of the HOC phase.
Strain glass state as the boundary of two phase transitions
NASA Astrophysics Data System (ADS)
Zhou, Zhijian; Cui, Jian; Ren, Xiaobing
2015-08-01
A strain glass state was found to be located between B2-B19’ (cubic to monoclinic) phase transition and B2-R (cubic to rhombohedral) phase transition in Ti49Ni51 alloys after aging process. After a short time aging, strong strain glass transition was observed, because the size of the precipitates is small, which means the strain field induced by the precipitates is isotropic and point-defect-like, and the distribution of the precipitates is random. After a long time aging, the average size of the precipitates increases. The strong strain field induced by the precipitates around them forces the symmetry of the matrix materials to conform to the symmetry of the crystalline structure of the precipitates, which results in the new phase transition. The experiment shows that there exists no well-defined boundary in the evolution from the strain glass transition to the new phase transition. Due to its generality, this glass mediated phase transition divergence scheme can be applied to other proper material systems to induce a more important new phase transition path, which can be useful in the field of phase transition engineering.
Strain glass state as the boundary of two phase transitions.
Zhou, Zhijian; Cui, Jian; Ren, Xiaobing
2015-01-01
A strain glass state was found to be located between B2-B19' (cubic to monoclinic) phase transition and B2-R (cubic to rhombohedral) phase transition in Ti49Ni51 alloys after aging process. After a short time aging, strong strain glass transition was observed, because the size of the precipitates is small, which means the strain field induced by the precipitates is isotropic and point-defect-like, and the distribution of the precipitates is random. After a long time aging, the average size of the precipitates increases. The strong strain field induced by the precipitates around them forces the symmetry of the matrix materials to conform to the symmetry of the crystalline structure of the precipitates, which results in the new phase transition. The experiment shows that there exists no well-defined boundary in the evolution from the strain glass transition to the new phase transition. Due to its generality, this glass mediated phase transition divergence scheme can be applied to other proper material systems to induce a more important new phase transition path, which can be useful in the field of phase transition engineering. PMID:26307500
Phase diagram of the ground states of DNA condensates.
Hoang, Trinh X; Trinh, Hoa Lan; Giacometti, Achille; Podgornik, Rudolf; Banavar, Jayanth R; Maritan, Amos
2015-12-01
The phase diagram of the ground states of DNA in a bad solvent is studied for a semiflexible polymer model with a generalized local elastic bending potential characterized by a nonlinearity parameter x and effective self-attraction promoting compaction. x=1 corresponds to the wormlike chain model. Surprisingly, the phase diagram as well as the transition lines between the ground states are found to be a function of x. The model provides a simple explanation for the results of prior experimental and computational studies and makes predictions for the specific geometries of the ground states. The results underscore the impact of the form of the microscopic bending energy at macroscopic observable scales. PMID:26764619
All solid-state SBS phase conjugate mirror
Dane, C.B.; Hackel, L.A.
1999-03-09
A stimulated Brillouin scattering (SBS) phase conjugate laser mirror uses a solid-state nonlinear gain medium instead of the conventional liquid or high pressure gas medium. The concept has been effectively demonstrated using common optical-grade fused silica. An energy threshold of 2.5 mJ and a slope efficiency of over 90% were achieved, resulting in an overall energy reflectivity of >80% for 15 ns, 1 um laser pulses. The use of solid-state materials is enabled by a multi-pass resonant architecture which suppresses transient fluctuations that would otherwise result in damage to the SBS medium. This all solid state phase conjugator is safer, more reliable, and more easily manufactured than prior art designs. It allows nonlinear wavefront correction to be implemented in industrial and defense laser systems whose operating environments would preclude the introduction of potentially hazardous liquids or high pressure gases. 8 figs.
All solid-state SBS phase conjugate mirror
Dane, Clifford B.; Hackel, Lloyd A.
1999-01-01
A stimulated Brillouin scattering (SBS) phase conjugate laser mirror uses a solid-state nonlinear gain medium instead of the conventional liquid or high pressure gas medium. The concept has been effectively demonstrated using common optical-grade fused silica. An energy threshold of 2.5 mJ and a slope efficiency of over 90% were achieved, resulting in an overall energy reflectivity of >80% for 15 ns, 1 um laser pulses. The use of solid-state materials is enabled by a multi-pass resonant architecture which suppresses transient fluctuations that would otherwise result in damage to the SBS medium. This all solid state phase conjugator is safer, more reliable, and more easily manufactured than prior art designs. It allows nonlinear wavefront correction to be implemented in industrial and defense laser systems whose operating environments would preclude the introduction of potentially hazardous liquids or high pressure gases.
NASA Astrophysics Data System (ADS)
Decreton, A.; Benigni, P.; Rogez, J.; Mikaelian, G.; Barrachin, M.; Lomello-Tafin, M.; Antion, C.; Janghorban, A.; Fischer, E.
2015-10-01
Most pressurized water reactor (PWR) absorber rods are composed of an Ag-In-Cd (SIC) alloy inside a stainless steel (SS) cladding, themselves inserted into a Zircaloy tube. During a severe accident, the SIC alloy which melts at 800 °C does not practically interact with SS. However, the cladding failure results from its internal pressurization and its eutectic interaction with Zircaloy and occurs at temperatures greater than 1200 °C. The subsequent interaction between the SIC melt and the Zircaloy has a strong impact on the quantities of aerosols released into the primary circuit and finally on the iodine chemistry. Accurate knowledge of the Ag-Zr system is a prerequisite to address this issue. Within this concern, our experimental work is focused both on the investigation of the Ag-Zr phase diagram and on the determination of the thermodynamic properties of the intermetallic compounds in the system. Two intermetallic compounds (AgZr and AgZr2) were identified. Ag-Zr cast alloys with a Ag/Zr ratio of 1:1 elaborated using an arc-melting furnace, once annealed, contained only a single phase AgZr. From metallographic observations, it appears that AgZr2 likely forms by the peritectic reaction from liquid and the bcc (βZr) phase. The partial enthalpies of solution of silver and zirconium in aluminum were experimentally determined at 723 °C in order to determine the enthalpies of formation of the intermetallic compounds. For silver solution calorimetry in aluminum bath, our measurements were successful and in agreement with the previous data. Yet, this study shows that liquid aluminum should not be used as a solvent for zirconium below 1000 °C.
Kikuchi, Azusa; Shibata, Kenji; Kumasaka, Ryo; Yagi, Mikio
2013-02-21
The excited states of UV-B absorber (4-methylbenzylidene)camphor (MBC) have been studied through measurements of UV absorption, phosphorescence, triplet-triplet (T-T) absorption, and steady-state and time-resolved electron paramagnetic resonance spectra in ethanol. The energy level and lifetime of the lowest excited triplet (T(1)) state of MBC were determined. The energy level of the T(1) state of MBC is much lower than that of photolabile 4-tert-butyl-4'-methoxydibenzoylmethane. The weak phosphorescence and strong time-resolved EPR signals, and T-T absorption band of MBC were observed. These facts suggest that the significant proportion of the lowest excited singlet (S(1)) molecules undergoes intersystem crossing to the T(1) state and the deactivation process from the T(1) state is predominantly radiationless. The quantum yields of singlet oxygen production by MBC determined by time-resolved near-IR luminescence measurements are 0.05 ± 0.01 and 0.06 ± 0.01 in ethanol and in acetonitrile, respectively. The photostability of MBC arises from the (3)ππ* character in the T(1) state. The zero-field splitting parameters in the T(1) state are D = 0.0901 cm(-1) and E = -0.0498 cm(-1). The sublevel preferentially populated by intersystem crossing is T(y) (y close to in-plane short axis and to the C═O direction). PMID:23320917
Semiempirical multi-phase Equation of state of Al
NASA Astrophysics Data System (ADS)
Zhang, Gongmu; Liu, Hai-Feng
2014-03-01
Equation of state (EOS) is the fundamental characteristic of matter determining its thermodynamic properties over a wide range of the phase diagram. EOS are based on a three-term Helmholtz free energy, given as a function of the specific volume V and temperature T. Semiempirical EOS use with great efficiency results obtained by theories and experimental data. Al serves as a standard material for high pressure region ,the EOS for this metal need to be especially exact and reliable. We construct the EOS for Al can describe the phase solid, liquid and gas, it agrees with IEX and DAC experiment data and the other theories data well.
Quantum Hall States and Phase Diagram of Bilayer Graphene
NASA Astrophysics Data System (ADS)
Jia, Junji
2013-03-01
The quantum Hall states of bilayer graphene for filling factor ν from 0 to 4 are investigated using lowest Landau level approximation. A critical line in the E⊥B plane for both the ν = 0 and 1 case is found. This line separates the (partially) spin polarized and (partially) layer polarized phases in the ν = 0 (1) case. The gaps for all ν are found to scale linearly with B. The existence of phase separation line, the linearity of the gaps, and the hierarchy for gaps of different ν agree well with experiments.
Dispersion cancellation with phase-sensitive Gaussian-state light
Shapiro, Jeffrey H.
2010-02-15
Franson's paradigm for nonlocal dispersion cancellation [J. D. Franson, Phys. Rev. A 45, 3126 (1992)] is studied using two kinds of jointly Gaussian-state signal and reference beams with phase-sensitive cross correlations. The first joint signal-reference state is nonclassical, with a phase-sensitive cross correlation that is at the ultimate quantum-mechanical limit. It models the outputs obtained from continuous-wave spontaneous parametric down-conversion. The second joint signal-reference state is classical--it has a proper P representation--with a phase-sensitive cross correlation that is at the limit set by classical physics. Using these states we show that a version of Franson's nonlocal dispersion cancellation configuration has essentially identical quantum and classical explanations except for the contrast obtained, which is much higher in the quantum case than it is in the classical case. This work bears on Franson's recent article [J. D. Franson, Phys. Rev. A 80, 032119 (2009)], which asserts that there is no classical explanation for all the features seen in quantum nonlocal dispersion cancellation.
State Legislation: Emerging Trends Reflected in the State Phase 1 Race to The Top Applications
ERIC Educational Resources Information Center
Learning Point Associates, 2010
2010-01-01
Through the American Recovery and Reinvestment Act (ARRA) of 2009, a significant amount of funding has been targeted to improve state and local education systems. The Race to the Top Fund in particular is providing $4.35 billion in competitive grants for states. The U.S. Department of Education designated two phases for the Race to the Top grant…
Solid State NMR Studies of the Aluminum Hydride Phases
NASA Technical Reports Server (NTRS)
Hwang, Son-Jong; Bowman, R. C., Jr.; Graetz, Jason; Reilly, J. J.
2006-01-01
Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the (beta)- and (gamma)- phases as well as the most stable (alpha)-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the (beta)-AlH3 and (gamma)-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the (alpha)-phase materials do not exhibit these changes.
Three-state selective population of dressed states via generalized spectral phase-step modulation
Wollenhaupt, Matthias; Bayer, Tim; Baumert, Thomas; Vitanov, Nikolay V.
2010-05-15
We present a joint experimental and theoretical study of selective population of dressed states (SPODS) in a three-level system. Control is exerted by shaped intense femtosecond laser pulses generated by a generalized spectral phase-step modulation function. We show that both control parameters (i.e., the phase-step amplitude and position) can be used to switch population among each three dressed states with high selectivity. The dynamics of the system, and hence the resulting photoelectron signal is studied theoretically by analyzing the time evolution of the adiabatic dressed-state energies and populations.
NASA Astrophysics Data System (ADS)
Pradhan, R.; Saha, S.; Datta, P. K.
2013-01-01
Round-trip phase-shifts with intensity of an input signal due to saturable index change and optically induced thermal effects in a vertical cavity semiconductor (quantum wells) saturable absorber (VCSSA) are investigated analytically to observe counter-clockwise bi-stability in transmission mode and clockwise bi-stability in reflection mode. Simultaneous effects of Kerr nonlinearity and cavity heating on resonance wavelength-shift of the VCSSA micro-cavity are investigated. It is found that these bi-stable characteristics are possible to the absorption edge of nonlinear material for long wavelength side operations of low intensity resonance wavelength of the micro-cavity, where dispersion of absorption and refraction are neglected over a small range of optical wavelength tuning (δλ˜10 nm). Simulations are carried out to find out optimized parameters of the device for bi-stable characteristics. Operations are demonstrated for InGaAs/InP quantum wells based VCSSA with low intensity resonance wavelength of 1570 nm. For counter-clockwise bi-stable switching at working wavelength of 1581 nm, an input intensity variation of 0.79IS is required with top (Rt) and back DBR reflectivity (Rb) of 91% and 93%, respectively, where IS represents the absorption saturation intensity of nonlinear medium. Whereas, the clockwise bi-stability occurs at 0.22IS for working wavelength of 1578 nm with Rt of 90% and Rb of 98%, respectively.
Sebesta, F.; John, J.; Motl, A.
1996-05-01
The performance of PAN-based composite absorbers was evaluated in dynamic experiments at flow rates ranging from 25--100 bed volumes (BV) per hour. Composite absorbers with active components of ammonium molybdophosphate (AMP) PAN and K-Co ferrocyanide (KCoFC) PAN were used for separating Cs from a 1 M HNO{sub 3} + 1 M NaNO{sub 3} + 2 {times} 10{sup {minus}5} M CsCl acidic simulant solution. KCoFC-PAN and two other FC-based composite absorbers were tested for separating Cs from alkaline simulant solutions containing 0.01 M to 1 M NaOH and 1 M NaNO{sub 3} + x {times} 10{sup {minus}4} M CsCl. The efficiency of the Cs sorption on the AMP-PAN absorber from acidic simulant solutions was negatively influenced by the dissolution of the AMP active component. At flow rates of 50 BV/hr, the decontamination factor of about 10{sup 3} could be maintained for treatment of 380 BV of the feed. With the KCoFC-PAN absorber, the decontamination factor of about 10{sup 3} could be maintained for a feed volume as great as 1,800 BV. In alkaline simulant solutions, significant decomposition of the active components was observed, and the best performance was exhibited by the KCoFC-PAN absorber. Introductory experiments confirmed that Cs may be washed out of the composite absorbers. Regeneration of both absorbers for repetitive use was also found to be possible. The main result of the study is that PAN was proven to be a versatile polymer capable of forming porous composite absorbers with a large number of primary absorbers. The composite absorbers proved to be capable of withstanding the harsh acidic and alkaline conditions and significant radiation doses that may be expected in the treatment of US DOE wastes. A field demonstration is proposed as a follow-on activity.
Phase State and Dynamics of Fluids in Mesoporous Solids
NASA Astrophysics Data System (ADS)
Valiullin, Rustem
2011-03-01
Fundamental understanding of the correlations between the phase state and dynamics of fluids confined to mesoporous solids is an important prerequisite for their optimal use in practical applications. The present contribution describes some recent progress in the exploration of such interrelations using nuclear magnetic resonance. In particular, transport properties of fluids during gas-liquid, solid-liquid and liquid-liquid transitions occurring in pore spaces of mesoporous solids are discussed and are shown to bear strong correlations. From the results presented it will, in particular, become evident that molecular diffusivity is a sensitive microscopic parameter not only to the thermodynamic state of the system, but also the history of its preparation.
NASA Astrophysics Data System (ADS)
Chyba, David Edward
This dissertation presents new results for the steady states of a detuned ring laser with a saturable absorber. The treatment is based on a semiclassical model which assumes homogeneously broadened two-level atoms. Part 1 presents a solution of the Maxwell-Bloch equations for the longitudinal dependence of the steady states of this system. The solution is then simplified by use of the mean field approximation. Graphical results in the mean field approximation are presented for squared electric field versus operating frequency, and for each of these versus cavity tuning and laser excitation. Various cavity linewidths and both resonant and non-resonant amplifier and absorber line center frequencies are considered. The most notable finding is that cavity detuning breaks the degeneracies previously found in the steady state solutions to the fully tuned case. This lead to the prediction that an actual system will bifurcate from the zero intensity solution to a steady state solution as laser excitation increases from zero, rather than to the small amplitude pulsations found for the model with mathematically exact tuning of the cavity and the media line centers. Other phenomena suggested by the steady state results include tuning-dependent hysteresis and bistability, and instability due to the appearance of another steady state solution. Results for the case in which the media have different line center frequencies suggest non-monotonic behavior of the electric field amplitude as laser excitation varies, as well as hysteresis and bistability. Part 2 presents a formulation of the linearized stability problem for the steady state solutions discussed in the first part. Thus the effects of detuning and the other parameters describing the system is incorporated into the stability analysis. The equations of the system are linearized about both the mean field steady states and about the longitudinally dependent steady states. Expansion in Fourier spatial modes is used in the
Phenomena of solid state grain boundaries phase transition in technology
NASA Astrophysics Data System (ADS)
Minaev, Y. A.
2015-03-01
The results of study the phenomenon, discovered by author (1971), of the phase transition of grain boundary by the formation of two-dimensional liquid or quasi-liquid films have been done. The described phenomena of the first order phase transition (two-dimensional melting) at temperatures 0.6 - 0.9 TS0 (of the solid state melting point) is a fundamental property of solid crystalline materials, which has allowed to revise radically scientific representations about a solid state of substance. Using the mathematical tools of the film thermodynamics it has been obtained the generalized equation of Clausius - Clapeyron type for two-dimensional phase transition. The generalized equation has been used for calculating grain boundary phase transition temperature TSf of any metal, which value lies in the range of (0.55…0.86) TS0. Based on these works conclusions the develop strategies for effective forming of coatings (by thermo-chemical processing) on surface layers of functional alloys and hard metals have been made. The short overview of the results of some graded alloys characterization has been done.
Phenomena of solid state grain boundaries phase transition in technology
Minaev, Y. A.
2015-03-30
The results of study the phenomenon, discovered by author (1971), of the phase transition of grain boundary by the formation of two-dimensional liquid or quasi-liquid films have been done. The described phenomena of the first order phase transition (two-dimensional melting) at temperatures 0.6 – 0.9 T{sub S0} (of the solid state melting point) is a fundamental property of solid crystalline materials, which has allowed to revise radically scientific representations about a solid state of substance. Using the mathematical tools of the film thermodynamics it has been obtained the generalized equation of Clausius - Clapeyron type for two-dimensional phase transition. The generalized equation has been used for calculating grain boundary phase transition temperature T{sub Sf} of any metal, which value lies in the range of (0.55…0.86) T{sub S0}. Based on these works conclusions the develop strategies for effective forming of coatings (by thermo-chemical processing) on surface layers of functional alloys and hard metals have been made. The short overview of the results of some graded alloys characterization has been done.
Li, Linsen; Chen-Wiegart, Yu-chen Karen; Wang, Jiajun; Gao, Peng; Ding, Qi; Yu, Young-Sang; Wang, Feng; Cabana, Jordi; Wang, Jun; Jin, Song
2015-01-01
In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge and charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. These mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries. PMID:25892338
Li, Linsen; Chen-Wiegart, Yu-chen Karen; Wang, Jiajun; Gao, Peng; Ding, Qi; Yu, Young-Sang; Wang, Feng; Cabana, Jordi; Wang, Jun; Jin, Song
2015-04-20
In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge and charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. In conclusion, these mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries.
Li, Linsen; Chen-Wiegart, Yu-chen Karen; Wang, Jiajun; Gao, Peng; Ding, Qi; Yu, Young-Sang; Wang, Feng; Cabana, Jordi; Wang, Jun; Jin, Song
2015-01-01
In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge and charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. These mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries. PMID:25892338
NASA Astrophysics Data System (ADS)
Li, Linsen; Chen-Wiegart, Yu-Chen Karen; Wang, Jiajun; Gao, Peng; Ding, Qi; Yu, Young-Sang; Wang, Feng; Cabana, Jordi; Wang, Jun; Jin, Song
2015-04-01
In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge and charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. These mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries.
Short-time dynamics of 2-thiouracil in the light absorbing S{sub 2}(ππ{sup ∗}) state
Jiang, Jie; Zhang, Teng-shuo; Xue, Jia-dan; Zheng, Xuming; Cui, Ganglong; Fang, Wei-hai
2015-11-07
Ultrahigh quantum yields of intersystem crossing to the lowest triplet state T{sub 1} are observed for 2-thiouracils (2TU), which is in contrast to the natural uracils that predominantly exhibit ultrafast internal conversion to the ground state upon excitation to the singlet excited state. The intersystem crossing mechanism of 2TU has recently been investigated using second-order perturbation methods with a high-level complete-active space self-consistent field. Three competitive nonadiabatic pathways to the lowest triplet state T{sub 1} from the initially populated singlet excited state S{sub 2} were proposed. We investigate the initial decay dynamics of 2TU from the light absorbing excited states using resonance Raman spectroscopy, time-dependent wave-packet theory in the simple model, and complete-active space self-consistent field (CASSCF) and time dependent-Becke’s three-parameter exchange and correlation functional with the Lee-Yang-Parr correlation functional (TD-B3LYP) calculations. The obtained short-time structural dynamics in easy-to-visualize internal coordinates were compared with the CASSCF(16,11) predicted key nonadiabatic decay routes. Our results indicate that the predominant decay pathway initiated at the Franck-Condon region is toward the S{sub 2}/S{sub 1} conical intersection point and S{sub 2}T{sub 3} intersystem crossing point, but not toward the S{sub 2}T{sub 2} intersystem crossing point.
Phase sensitivity in deformed-state superposition considering nonlinear phase shifts
NASA Astrophysics Data System (ADS)
Berrada, K.
2016-07-01
We study the problem of the phase estimation for the deformation-state superposition (DSS) under perfect and lossy (due to a dissipative interaction of DSS with their environment) regimes. The study is also devoted to the phase enhancement of the quantum states resulting from a generalized non-linearity of the phase shifts, both without and with losses. We find that such a kind of superposition can give the smallest variance in the phase parameter in comparison with usual Schrödinger cat states in different order of non-linearity even if for a larger average number of photons. Due to the significance of how a system is quantum correlated with its environment in the construction of a scalable quantum computer, the entanglement between the DSS and its environment is investigated during the dissipation. We show that partial entanglement trapping occurs during the dynamics depending on the kind of deformation and mean photon number. These features make the DSS with a larger average number of photons a good candidate for implementation of schemes of quantum optics and information with high precision.
Partially coherent twisted states in arrays of coupled phase oscillators
Omel'chenko, Oleh E.; Wolfrum, Matthias; Laing, Carlo R.
2014-06-15
We consider a one-dimensional array of phase oscillators with non-local coupling and a Lorentzian distribution of natural frequencies. The primary objects of interest are partially coherent states that are uniformly “twisted” in space. To analyze these, we take the continuum limit, perform an Ott/Antonsen reduction, integrate over the natural frequencies, and study the resulting spatio-temporal system on an unbounded domain. We show that these twisted states and their stability can be calculated explicitly. We find that stable twisted states with different wave numbers appear for increasing coupling strength in the well-known Eckhaus scenario. Simulations of finite arrays of oscillators show good agreement with results of the analysis of the infinite system.
NASA Astrophysics Data System (ADS)
Conny, J. M.; Ma, X.; Gunn, L. R.
2011-12-01
Particles with heterogeneously-distributed light-absorbing and light-scattering phases were generated from incomplete combustion or thermal decomposition to mimic real atmospheric particles with distinctive optical properties. Individual particles and particle populations were characterized microscopically. The purpose was to examine how optical property measurements of internally-mixed ambient air particles might vary based on the properties of laboratory-generated particles produced under controlled conditions. The project is an initial stage in producing reference samples for calibrating instrumentation for monitoring climatically-important atmospheric aerosols. Binary-phase particles containing black carbon (BC) and a metal or a metal oxide phase were generated from the thermal decomposition or partial combustion of liquid fuels at a variety of temperatures from 600 °C to 1100 °C. Fuels included mixtures of toluene or isooctane and iron pentacarbonyl or titanium tetrachloride. Scanning electron microscopy with energy-dispersive x-ray spectroscopy revealed that burning the fuels at different temperatures resulted in distinctive differences in morphology and carbon vs. metal/metal oxide composition. Particles from toluene/Fe(CO)5 thermal decomposition exhibited aggregated morphologies that were classified as dendritic, soot-like, globular, or composited (dendritic-globular). Particles from isooctane/TiCl4 combustion were typically spherical with surface adducts or aggregates. Diameters of the BC/TiO2 particles averaged 0.68 μm to 0.70 μm. Regardless of combustion temperature, the most abundant particles in each BC/TiO2 sample had an aspect ratio of 1.2. However, for the 600 °C and 900 °C samples the distribution of aspect ratios was skewed toward much larger ratios suggesting significant chainlike aggregation. Carbon and titanium compositions (wt.) for the 600 °C sample were 12 % and 53 %, respectively. In contrast, the composition trended in the opposite
Dimensionless Equation of State to Predict Microemulsion Phase Behavior.
Ghosh, Soumyadeep; Johns, Russell T
2016-09-01
Prediction of microemulsion phase behavior for changing state variables is critical to formulation design of surfactant-oil-brine (SOB) systems. SOB systems find applications in various chemical and petroleum processes, including enhanced oil recovery. A dimensional equation-of-state (EoS) was recently presented by Ghosh and Johns1 that relied on estimation of the surfactant tail length and surface area. We give an algorithm for flash calculations for estimation of three-phase Winsor regions that is more robust, simpler, and noniterative by making the equations dimensionless so that estimates of tail length and surface area are no longer needed. We predict phase behavior as a function temperature, pressure, volume, salinity, oil type, oil-water ratio, and surfactant/alcohol concentration. The dimensionless EoS is based on coupling the HLD-NAC (Hydrophilic Lipophilic Difference-Net Average Curvature) equations with new relationships between optimum salinity and solubility. An updated HLD expression that includes pressure is also used to complete the state description. A significant advantage of the dimensionless form of the EoS over the dimensional version is that salinity scans are tuned based only on one parameter, the interfacial volume ratio. Further, stability conditions are developed in a simplified way to predict whether an overall compositions lies within the single, two-, or three-phase regions. Important new microemulsion relationships are also found, the most important of which is that optimum solubilization ratio is equal to the harmonic mean of the oil and water solubilization ratios in the type III region. Thus, only one experimental measurement is needed in the three-phase zone to estimate the optimum solubilization ratio, a result which can aid experimental design and improve estimates of optimum from noisy data. Predictions with changing state variables are illustrated by comparison to experimental data using standard diagrams including a new type
Equation of state and phase diagram of FeO
Fischer, Rebecca A.; Campbell, Andrew J.; Shofner, Gregory A.; Lord, Oliver T.; Dera, Przemyslaw; Prakapenka, Vitali B.
2012-04-11
Wuestite, Fe{sub 1-x}O, is an important component in the mineralogy of Earth's lower mantle and may also be a component in the core. Therefore the high pressure, high temperature behavior of FeO, including its phase diagram and equation of state, is essential knowledge for understanding the properties and evolution of Earth's deep interior. We performed X-ray diffraction measurements using a laser-heated diamond anvil cell to achieve simultaneous high pressures and temperatures. Wuestite was mixed with iron metal, which served as our pressure standard, under the assumption that negligible oxygen dissolved into the iron. Our data show a positive slope for the subsolidus phase boundary between the B1 and B8 structures, indicating that the B1 phase is stable at the P-T conditions of the lower mantle and core. We have determined the thermal equation of state of B1 FeO to 156 GPa and 3100 K, finding an isothermal bulk modulus K{sub 0} = 149.4 {+-} 1.0 GPa and its pressure derivative K'{sub 0} = 3.60 {+-} 0.4. This implies that 7.7 {+-} 1.1 wt.% oxygen is required in the outer core to match the seismologically-determined density, under the simplifying assumption of a purely Fe-O outer core.
Semiempirical multi-phase Equation of state of Al
NASA Astrophysics Data System (ADS)
Zhang, Gongmu; Liu, Haifeng; Zhao, Yanhong; Iapcm Eos Team
2013-06-01
Equation of state(EOS) is the fundamental characteristic of matter determining its thermodynamic properties over a wide range of the phase diagram. EOS are based on a three-term Helmholtz free energy, given as a function of the specific volume V and temperature T. Semiempirical EOS use with great efficiency results obtained by theories and experimental data. Al serves as a standard material for high pressure region, the EOS for this metal need to be especially exact and reliable. We construct the EOS for Al can describe the phase solid, liquid and gas, it agrees with IEX and DAC experiment data and the other theories data well. This research is supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics (Grant No. 2010A0101001).
Parameter estimation of qubit states with unknown phase parameter
NASA Astrophysics Data System (ADS)
Suzuki, Jun
2015-02-01
We discuss a problem of parameter estimation for quantum two-level system, qubit system, in presence of unknown phase parameter. We analyze trade-off relations for mean square errors (MSEs) when estimating relevant parameters with separable measurements based on known precision bounds; the symmetric logarithmic derivative (SLD) Cramér-Rao (CR) bound and Hayashi-Gill-Massar (HGM) bound. We investigate the optimal measurement which attains the HGM bound and discuss its properties. We show that the HGM bound for relevant parameters can be attained asymptotically by using some fraction of given n quantum states to estimate the phase parameter. We also discuss the Holevo bound which can be attained asymptotically by a collective measurement.
Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs
NASA Technical Reports Server (NTRS)
Chen, C.-C.; Win, M. Z.
1991-01-01
The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.
Ground-state phases of polarized deuterium species
Panoff, R.M.; Clark, J.W.
1987-10-01
Microscopic prediction of the ground-state phase of electron-spin-aligned bulk atomic deuterium (Darrow-down) is attempted, based on the variational Monte Carlo method. The accurate pair potential of Kolos and Wolniewicz is assumed, and three versions of Darrow-down are considered, which, respectively, involve one, two, and three equally occupied nuclear spin states. The most definitive results on the zero-temperature equations of state of these systems are obtained with optimized ground-state trial wave functions incorporating Jastrow pair correlations, triplet correlations, and momentum-dependent backflow effects. The species Darrow-down/sub 3/ is bound already at the pure Jastrow level, while the energy expectation value of Darrow-down/sub 2/ dips below zero upon supplementing the Jastrow description by triplets and momentum-dependent backflow. The variational energy of Darrow-down/sub 1/ remains positive under all current refinements of the ground-state trial function. We conclude that the systems Darrow-down/sub 3/ and Darrow-down/sub 2/, if they could be manufactured and stabilized at relevant densities, would be Fermi liquids at sufficiently low temperature; on the other hand, it is likely that Darrow-down/sub 1/ would remain gaseous down to absolute zero.
Raetsep, M.; Johnson, T.W.; Chitnis, P.R.; Small, G.J.
2000-02-03
Low temperature (4.2 K) absorption and hole-burned spectra are presented for the trimeric (wild-type, WT) photosystem I complex of the cyanobacterium Synechocystis sp. PCC 6803, its monomeric form, and mutants deficient in the PsaF, K, L, and M protein subunits. High-pressure- and Stark-hole-burning data for the WT trimer are presented as well as its temperature-dependent Q{sub y}-absorption and -fluorescence spectra. Taken as a whole, the data lead to assignment of a new and lowest energy antenna Q{sub y}-state located at 714 nm at low temperatures. It is this state that is responsible for the fluorescence in the low-temperature limit and not the previously identified antenna Q{sub y}-state near 708 nm. The data indicate that the 714 nm state is associated with strongly coupled chlorophyll a molecules (perhaps a dimer) and possesses significant charge transfer character. The red chlorophylls absorbing at 708 and 714 nm do not appear to be directly bound to any of the above protein subunits. The results are consistent with a location close to the interfacial regions between PsaL and M and the PsaA/B heterodimeric core. It is likely that the red chlorophylls are bound to PsaA and/or PsaB.
Economical Gaussian cloning of coherent states with known phase
Dong Yuli; Zou Xubo; Guo Guangcan; Li Shangbin
2007-07-15
We investigate the economical Gaussian cloning of coherent states with the known phase, which produces M copies from N input replica and can be implemented with degenerate parametric amplifiers and beam splitters.The achievable fidelity of single copy is given by 2M{radical}(N)/[{radical}(N)(M-1)+{radical}((1+N)(M{sup 2}+N))], which is bigger than the optimal fidelity of the universal Gaussian cloning. The cloning machine presented here works without ancillary optical modes and can be regarded as the continuous variable generalization of the economical cloning machine for qudits.
Phenomenology and energetics of diffusion across cell phase states
Ashrafuzzaman, Md.
2015-01-01
Cell based transport properties have been mathematically addressed. Cell contained cross boundary diffusion of materials has been explained using valid formalisms and related analytical expressions have been developed. Various distinguishable physical structures and their properties raise different general structure specific diffusion mechanisms and controlled transport related parameters. Some of these parameters play phenomenological roles and some cause regulatory effects. The cell based compartments may be divided into three major physical phase states namely liquid, plasma and solid phase states. Transport of ions, nutrients, small molecules like proteins, etc. across inter phase states and intraphase states follows general transport related formalisms. Creation of some localized permanent and/or temporary structures e.g., ion channels, clustering of constituents, etc. and the transitions between such structures appear as regulators of the transport mechanisms. In this article, I have developed mainly a theoretical analysis of the commonly observed cell transport phenomena. I have attempted to develop formalisms on general cell based diffusion followed by a few numerical computations to address the analytical expression phenomenologically. I have then extended the analysis to adopting with the local structure originated energetics. Independent or correlated molecular transport naturally relies on some general parameters that define the nature of local cell environment as well as on some occasionally raised or transiently active stochastic resonance due to localized interactions. Short and long range interaction energies play crucial roles in this regard. Physical classification of cellular compartments has led us developing analytical expressions on both biologically observed diffusion mechanisms and the diffusions’s occasional stochasticity causing energetics. These analytical expressions help us address the diffusion phenomena generally considering the
Phenomenology and energetics of diffusion across cell phase states.
Ashrafuzzaman, Md
2015-11-01
Cell based transport properties have been mathematically addressed. Cell contained cross boundary diffusion of materials has been explained using valid formalisms and related analytical expressions have been developed. Various distinguishable physical structures and their properties raise different general structure specific diffusion mechanisms and controlled transport related parameters. Some of these parameters play phenomenological roles and some cause regulatory effects. The cell based compartments may be divided into three major physical phase states namely liquid, plasma and solid phase states. Transport of ions, nutrients, small molecules like proteins, etc. across inter phase states and intraphase states follows general transport related formalisms. Creation of some localized permanent and/or temporary structures e.g., ion channels, clustering of constituents, etc. and the transitions between such structures appear as regulators of the transport mechanisms. In this article, I have developed mainly a theoretical analysis of the commonly observed cell transport phenomena. I have attempted to develop formalisms on general cell based diffusion followed by a few numerical computations to address the analytical expression phenomenologically. I have then extended the analysis to adopting with the local structure originated energetics. Independent or correlated molecular transport naturally relies on some general parameters that define the nature of local cell environment as well as on some occasionally raised or transiently active stochastic resonance due to localized interactions. Short and long range interaction energies play crucial roles in this regard. Physical classification of cellular compartments has led us developing analytical expressions on both biologically observed diffusion mechanisms and the diffusions's occasional stochasticity causing energetics. These analytical expressions help us address the diffusion phenomena generally considering the
Geometric phases causing lifetime modifications of metastable states of hydrogen
NASA Astrophysics Data System (ADS)
Trappe, Martin-Isbjörn; Augenstein, Peter; DeKieviet, Maarten; Gasenzer, Thomas; Nachtmann, Otto
2016-04-01
Externally applied electromagnetic fields in general have an influence on the width of atomic spectral lines. The decay rates of atomic states can also be affected by the geometry of an applied field configuration giving rise to an imaginary geometric phase. A specific chiral electromagnetic field configuration is presented which geometrically modifies the lifetimes of metastable states of hydrogen. We propose to extract the relevant observables in a realistic longitudinal atomic beam spin-echo apparatus which allows the initial and final fluxes of the metastable atoms to be compared with each other interferometrically. A geometry-induced change in lifetimes at the 5%-level is found, an effect large enough to be observed in an available experiment.
Semiclassical Dynamics of Electron Wave Packet States with Phase Vortices
Bliokh, Konstantin Yu.; Bliokh, Yury P.; Savel'ev, Sergey; Nori, Franco
2007-11-09
We consider semiclassical higher-order wave packet solutions of the Schroedinger equation with phase vortices. The vortex line is aligned with the propagation direction, and the wave packet carries a well-defined orbital angular momentum (OAM) ({Dirac_h}/2{pi})l (l is the vortex strength) along its main linear momentum. The probability current coils around the momentum in such OAM states of electrons. In an electric field, these states evolve like massless particles with spin l. The magnetic-monopole Berry curvature appears in momentum space, which results in a spin-orbit-type interaction and a Berry/Magnus transverse force acting on the wave packet. This brings about the OAM Hall effect. In a magnetic field, there is a Zeeman interaction, which, can lead to more complicated dynamics.
Competing reaction model with many absorbing configurations.
de Andrade, M F; Figueiredo, W
2010-02-01
We study a competitive reaction model between two monomers A and B on a linear lattice. We assume that monomer A can react with a nearest-neighbor monomer A or B , but reactions between monomers of type B are prohibited. We include in our model lateral interactions between monomers as well as the effects of temperature of the catalyst. The model is considered in the adsorption controlled limit, where the reaction rate is infinitely larger than the adsorption rate of the monomers. We employ site and pair mean-field approximations as well as static Monte Carlo simulations. We determine the phase diagram of the model in the plane y_{A} versus temperature, where y_{A} is the probability that a monomer of the type A arrives at the surface. This phase diagram shows regions of active and absorbing states separated by a line of continuous phase transitions. Despite the absorbing state of the model to be strongly dependent on temperature, we show that the static critical exponents of the model belong to the same universality class of the directed percolation. PMID:20365537
Ground-state phase diagram of the quantum Rabi model
NASA Astrophysics Data System (ADS)
Ying, Zu-Jian; Liu, Maoxin; Luo, Hong-Gang; Lin, Hai-Qing; You, J. Q.
2015-11-01
The Rabi model plays a fundamental role in understanding light-matter interaction. It reduces to the Jaynes-Cummings model via the rotating-wave approximation, which is applicable only to the cases of near resonance and weak coupling. However, recent experimental breakthroughs in upgrading light-matter coupling order require understanding the physics of the full quantum Rabi model (QRM). Despite the fact that its integrability and energy spectra have been exactly obtained, the challenge to formulate an exact wave function in a general case still hinders physical exploration of the QRM. Here we unveil a ground-state phase diagram of the QRM, consisting of a quadpolaron and a bipolaron as well as their changeover in the weak-, strong-, and intermediate-coupling regimes, respectively. An unexpected overweighted antipolaron is revealed in the quadpolaron state, and a hidden scaling behavior relevant to symmetry breaking is found in the bipolaron state. An experimentally accessible parameter is proposed to test these states, which might provide novel insights into the nature of the light-matter interaction for all regimes of the coupling strengths.
Tikhomirov, A. V.; Ponomarenko, G. L.
2012-07-01
An additional verification of bundled software (BS) SAPFIR-95 and amp;RC [1] and code KORSAR/GP [2] was performed. Both software products were developed in A.P. Alexandrov NITI and certified by ROSTEKHNADZOR of RF for numeric simulation of stationary, transitional and emergency conditions of VVER reactors. A benchmark model for neutronics calculations was created within the limits of this work. The cold subcritical state of VVER - 1000 reactor stationary fuelling was simulated on the basis of FA with an increased height of the fuel column (TVS-2M) considering detailed presentation of radial and front neutron reflectors. A case of passing of pure condensate slug through the core in initially deep subcritical state during start of the first RCP set after refueling was considered as an examined condition of reactor operation. A relatively small size of the slug, its spatial position near the reflectors (lower and lateral), as well as failure of the inserted control rods of the control and protection system (CPS CR) to reach the lower limit of the fuel column stipulate for methodical complexity of a correct calculation of the neutron multiplication constant (K{sub eff}) using engineering codes. Code RC was used as a test program in the process of reactor calculated 3-D modeling. Code MCNP5 [3] was used as the precision program, which solves the equation of neutrons transfer by Monte-Carlo method and which was developed in the US (Los-Alamos). As a result of comparative calculations dependency of K{sub eff} on two parameters was evaluated - boron acid concentration (Cb) and CPS CR position. Reactivity effect was evaluated, which is implemented as a result of failure of all CPS control rods to reach the lower fuel limit calculated using the engineering codes mentioned above. (authors)
Recoupling in solid state NMR using γ prepared states and phase matching
Lin, James; Griffin, R.G.; Khaneja, Navin
2014-01-01
The paper describes two-dimensional solid state NMR experiments that use powdered dephased anti-phase coherence (γ preparation) to encode chemical shifts in the indirect dimension. Both components of this chemical shift encoded gamma-prepared states can be refocused into inphase coherence by a recoupling element. This helps to achieve sensitivity enhancement in 2D NMR experiments by quadrature detection. The powder dependence of the gamma-prepared states allows for manipulating them by suitable insertion of delays in the recoupling periods. This helps to design experiments that suppress diagonal peaks in 2D spectra, leading to improved resolution. We describe some new phase modulated heteronuclear and homonuclear recoupling pulse sequences that simplify the implementation of the described experiments based on γ prepared states. Recoupling in the heteronuclear spin system is achieved by matching the difference in the amplitude of the sine/cosine modulated phase on the two rf-channels to the spinning frequency while maintaining the same power on the two rf-channels. PMID:21889380
Majorana fermions and Dirac edge states in topological phases
NASA Astrophysics Data System (ADS)
Shivamoggi, Vasudha Bhimsen
In part 1, we study a realization of a chain of Majorana bound states at the interfaces between alternating ferromagnetic and superconducting regions at a quantum spin Hall insulator edge. In the limit of well separated Majoranas, the system can be mapped to the transverse field Ising model. The disordered critical point can be reached by tuning the relative magnitude or phases of the ferromagnetic and superconducting order parameters. We compute the voltage dependence of the tunneling current from a metallic tip into the Majorana chain as a direct probe of the random critical state. In part 2, we present an analytic prescription for computing the edge dispersion E( k) of a tight-binding Dirac Hamiltonian terminated at an abrupt crystalline edge. Specifically, we consider translationally invariant Dirac Hamiltonians with nearest-layer interaction. We present and prove a geometric formula that relates the existence of surface states as well as their energy dispersion to properties of the bulk Hamiltonian. We further prove the bulk-boundary correspondence between the Chern number and the chiral edge modes for quantum Hall systems within the class of Hamiltonians studied in the paper. Our results can be extended to the case of continuum theories which are quadratic in the momentum, as well as other symmetry classes.
40 CFR 72.73 - State issuance of Phase II permits.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 16 2010-07-01 2010-07-01 false State issuance of Phase II permits. 72.73 Section 72.73 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.73 State issuance of Phase II permits. (a) State Permit Issuance. (1) A...
Structural-phase state and creep of mixed nitride fuel
NASA Astrophysics Data System (ADS)
Konovalov, I. I.; Tarasov, B. A.; Glagovsky, E. M.
2016-04-01
By the analysis of thermal creep data in conjunction with structural-phase state the most likely mechanisms of UN creep are considered. An equation relating the thermal and radiation creep of nitride fuel with such important parameters as plutonium content, porosity, grain size, the content of impurities of transition metals and oxygen, the carbon content has been suggested. At stationary operating parameters in reactor the creep of nitride fuel with technical purity is defined by the thermal component at mechanism of intergranular slip and by the radiation component, which plays a significant role at temperatures below 1100°C. Both types of creep in a first approximation have a linear dependence on the stress.
Bhattacharyya, Sirshendu; Dasgupta, Subinay; Das, Arnab
2015-01-01
Understanding phase transitions in quantum matters constitutes a significant part of present day condensed matter physics. Quantum phase transitions concern ground state properties of many-body systems, and hence their signatures are expected to be pronounced in low-energy states. Here we report signature of a quantum critical point manifested in strongly out-of-equilibrium states with finite energy density with respect to the ground state and extensive (subsystem) entanglement entropy, generated by an external pulse. These non-equilibrium states are evidently completely disordered (e.g., paramagnetic in case of a magnetic ordering transition). The pulse is applied by switching a coupling of the Hamiltonian from an initial value (λI) to a final value (λF) for sufficiently long time and back again. The signature appears as non-analyticities (kinks) in the energy absorbed by the system from the pulse as a function of λF at critical-points (i.e., at values of λF corresponding to static critical-points of the system). As one excites higher and higher eigenstates of the final Hamiltonian H(λF) by increasing the pulse height , the non-analyticity grows stronger monotonically with it. This implies adding contributions from higher eigenstates help magnifying the non-analyticity, indicating strong imprint of the critical-point on them. Our findings are grounded on exact analytical results derived for Ising and XY chains in transverse field. PMID:26568306
Berry phases emerging from the π-flux state
NASA Astrophysics Data System (ADS)
Tanaka, Akihiro; Hu, Xiao
2005-03-01
We derive a new effective action describing fluctuations around the Affleck-Marston π-flux mean-field solution of the 2d Heisenberg antiferromagnet. The 5-dimensional Clifford algebra inherent in the Dirac fermion obtained as the continuum limit of the π-flux state is found to sustain a bulit-in competition between antiferromagnet (AF) and valence-bond-solid (VBS) orders. This naturally leads us to cast both orderings as components of a 5 component vectorial field v, for which we obtain an O(5) nonlinear sigma model with a novel Wess- Zumino (WZ) term proportional to the Mauer-Cartan form 0^1 dtd^3 x v dv dv dv dv, with t[0,1] an auxiliary variable which extends v(x) to v(t,x) in such a way that v(t=0,x)≡(0,0,0,0,1) and v(t=1,x)≡v(x) are satisfied. We study properties of Berry phases extracted from this WZ term, and recover in particular the AF hedgehog Berry phases (with a VBS core) which are central to recent studies on 2D spin liquids.
NASA Astrophysics Data System (ADS)
Qi, Yadong; Bai, Shuju; Gao, Wei; Heisler, Gordon M.
2003-06-01
Increased concentration of leaf UV-B absorbing-compounds due to exposure to UV-B radiation is widely accepted as one of the plant adaptations to resist enhanced UV-B radiation. This paper reports a field comparative study of dynamics and temporal changes of UV-B absorbing-compound concentration in 35 southern broadleaf trees over a growing season. Leaf UV-B absorbing-compound, chlorophyll concentration, and leaf thickness were measured from the sun-exposed leaves of 35 tree species collected monthly from individual trees growing within the city of Baton Rouge, Louisiana from April to October in 2000. The USDA UV-B Monitoring Network Baton Rouge Station provided the ambient UV-B radiation data. Leaf UV-B absorbing-compound concentration varied significantly with leaf age and species. Intra-specifically, leaf UV-B absorbing-compound concentration exhibited a generally increasing trend during leaf growth and development in response to the increased exposure to natural UV-B/solar radiation during the growing season. Inter-specifically, significant differences existed in leaf UV-B absorbing-compound concentration. The species were compared and ranked based on the growing season averages of the leaf total UV-B absorbing-compound concentration. The species were further classified into three levels (high, medium, and low) based on the magnitude of UV-B absorbing-compound concentration.
Gunalp, Bengul
2015-07-01
Myocardial perfusion imaging (MPI) is one the most contributing nuclear medicine technique to the annual population dose. The purpose of this study is to compare radiation-absorbed doses to the patients examined by conventional cardiac SPECT (CSPECT) camera and ultrafast cardiac (UFC) camera with cadmium-zinc-telluride (CZT) solid-state detectors. Total injected activity was reduced by 50 % when both stress and rest images were acquired and by 75 % when only stress images were taken with UFC camera. As a result of this, the mean total effective dose was found significantly lower with UFC camera (2.2 ± 1.2 mSv) than CSPECT (7.7 ± 3.8 mSv) (p < 0.001). Further dose reduction was obtained by reducing equivocal test results and unnecessary additional examinations with UFC camera. Using UFC camera, MPI can be conveniently used for the detection of coronary artery disease (CAD) much less increasing annual population radiation dose as it had been before. PMID:25848109
NASA Astrophysics Data System (ADS)
Den Blanken, H. J.; Van Der Zwet, G. P.; Hoff, A. J.
1982-01-01
We have measured zero-field resonance transitions of the triplet state of the primary donor monitoring the transmittance at 890 nm at 1.2 K in isolated reaction centers of Rhodopseudomonas sphaeroides R-26. The transitions correspond to a decrease in transmittance, confirming the energy transfer model for the transitions detected via the antenna fluorescence in whole cells.
Geometric phase of mixed states for three-level open systems
Jiang Yanyan; Ji, Y. H.; Wang, Z. S.; Xu Hualan; Hu Liyun; Chen, Z. Q.; Guo, L. P.
2010-12-15
Geometric phase of mixed state for three-level open system is defined by establishing in connecting density matrix with nonunit vector ray in a three-dimensional complex Hilbert space. Because the geometric phase depends only on the smooth curve on this space, it is formulated entirely in terms of geometric structures. Under the limiting of pure state, our approach is in agreement with the Berry phase, Pantcharatnam phase, and Aharonov and Anandan phase. We find that, furthermore, the Berry phase of mixed state correlated to population inversions of three-level open system.
Carbon Absorber Retrofit Equipment (CARE)
Klein, Eric
2015-12-23
During Project DE-FE0007528, CARE (Carbon Absorber Retrofit Equipment), Neumann Systems Group (NSG) designed, installed and tested a 0.5MW NeuStream® carbon dioxide (CO_{2}) capture system using the patented NeuStream® absorber equipment and concentrated (6 molal) piperazine (PZ) as the solvent at Colorado Springs Utilities’ (CSU’s) Martin Drake pulverized coal (PC) power plant. The 36 month project included design, build and test phases. The 0.5MW NeuStream® CO_{2} capture system was successfully tested on flue gas from both coal and natural gas combustion sources and was shown to meet project objectives. Ninety percent CO_{2} removal was achieved with greater than 95% CO_{2}product purity. The absorbers tested support a 90% reduction in absorber volume compared to packed towers and with an absorber parasitic power of less than 1% when configured for operation with a 550MW coal plant. The preliminary techno-economic analysis (TEA) performed by the Energy and Environmental Research Center (EERC) predicted an over-the-fence cost of $25.73/tonne of CO_{2} captured from a sub-critical PC plant.
Phase-Conjugate Receiver for Gaussian-State Quantum Illumination
NASA Technical Reports Server (NTRS)
Erkmen, Baris I.; Guha, Saikat
2010-01-01
An active optical sensor probes a region of free space that is engulfed in bright thermal noise to determine the presence (or absence) of a weakly reflecting target. The returned light (which is just thermal noise if no target is present, and thermal noise plus a weak reflection of the probe beam if a target is present) is measured and processed by a receiver and a decision is made on whether a target is present. It has been shown that generating an entangled pair of photons (which is a highly nonclassical state of light), using one photon as the probe beam and storing the other photon for comparison to the returned light, has superior performance to the traditional classical-light (coherent-state) target detection sensors. An entangled-photon transmitter and optimal receiver combination can yield up to a factor of 4 (i.e., 6 dB) gain in the error-probability exponent over a coherent state transmitter and optimal receiver combination, in a highly lossy and noisy scenario (when both sensors have the same number of transmitted photons). However, the receiver that achieves this advantage is not known. One structured receiver can close half of the 6-dB gap (i.e., a 3-dB improvement). It is based on phase-conjugating the returned light, then performing dual-balanced difference detection with the stored half of the entangled-photon pair. Active optical sensors are of tremendous value to NASA s missions. Although this work focuses on target detection, it can be extended to imaging (2D, 3D, hyperspectral, etc.) scenarios as well, where the image quality can be better than that offered by traditional active sensors. Although the current work is theoretical, NASA s future missions could benefit significantly from developing and demonstrating this capability. This is an optical receiver design whose components are, in principle, all implementable. However, the work is currently entirely theoretical. It is necessary to: 1. Demonstrate a bench-top proof of the theoretical
Lee, Jong Hoon; Naumov, Pance; Chung, Ihn Hee; Lee, Sang Cheol
2011-09-01
The lower 1,3-bis(hydroxyalkylamino) homologues of the strong intramolecular X-type charge transfer (CT) system 1,3-diamino-4,6-dinitrobenzene (DADNB) exhibit reversible color change in the solid state from yellow at room temperature (RT) to orange and red at high temperature (HT). To investigate the structural prerequisites for occurrence of this phenomenon, we prepared 10 new derivatives of DADNB where the hydroxyalkyl arms at the amino groups were replaced with substituents having different electronic and steric profiles. Two of the new materials exhibit sharp and reversible thermochromic change in the solid state: when heated, the bis(aminoethyl) derivative (DADNB-1) undergoes color change from orange-red to brown, while one of the three polymorphs of the bisphenyl product (DADNB-2) changes its color from red to yellow. The physicochemical analysis and the crystal structures of seven of these compounds, one of which is trimorphic, confirmed that both phenomena are due to solid-solid phase transitions. The brown high-temperature phase of DADNB-1 presents the first example where the absorption is shifted beyond the red region. Form C of DADNB-2 is the first material of this group that exhibits "negative" thermochromism, where the high-temperature phase absorbs at lower wavelength than the low-temperature one. The results demonstrate the potentials of these simple and easily accessible organic molecular materials for thermal switching of the optical properties by utility of intermolecular interactions to modulate the intramolecular CT. PMID:21790159
Composition for absorbing hydrogen
Heung, L.K.; Wicks, G.G.; Enz, G.L.
1995-05-02
A hydrogen absorbing composition is described. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.
Composition for absorbing hydrogen
Heung, Leung K.; Wicks, George G.; Enz, Glenn L.
1995-01-01
A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.
A solid-state phase-insensitive ultrasonic transducer
NASA Technical Reports Server (NTRS)
Heyman, J. S.
1979-01-01
Photoconductive acoustoelectric transducer (AET) functions as phase-insensitive ultrasonic transducer. Device is easy to use and requires no additional noisy components such as light or thermal source.
Bilger, Wolfgang; Björkman, Olle; Thayer, Susan S.
1989-01-01
When cotton (Gossypium hirsutum L., cv Acaia SJC-1) leaves kept in weak light were suddenly exposed to strong red actinic light a spectral absorbance change took place having the following prominent characteristics. (a) It was irreversible within the first four minute period after darkening. (b) The difference in leaf absorbance between illuminated and predarkened leaves had a major peak at 505 nanometers, a minor peak at 465 nanometers, a shoulder around 515 nanometers, and minor troughs at 455 and 480 nanometers. (c) On the basis of its spectral and kinetic characteristics this absorbance change can be readily distinguished from the much faster electrochromic shift which has a peak at 515 nanometers, from the slow, so-called light-scattering change which has a broad peak centered around 535 nanometers and is reversed upon darkening, and from absorbance changes associated with light-induced chloroplast rearrangements. (d) The extent and time course of this absorbance change closely matched that of the deepoxidation of violaxanthin to zeaxanthin in the same leaves. (e) Both the absorbance change and the ability to form zeaxanthin were completely blocked in leaves to which dithiothreitol (DTT) had been provided through the cut petlole. DTT treatment also caused strong inhibition of that component of the 535-nanometer absorbance change which is reversed in less than 4 minutes upon darkening and considered to be caused by increased light scattering. Moreover, DTT inhibited a large part of nonphotochemical quenching of chlorophyll fluorescence in the presence of excessive light. However, DTT had no detectable effect on the photon yield of photosynthesis measured under strictly rate-limiting photon flux densities or on the light-saturated photosynthetic capacity, at least in the short term. We conclude that it is possible to monitor light-induced violaxanthin de-epoxidation in green intact leaves by measurement of the absorbance change at 505 nanometers. Determination
NASA Astrophysics Data System (ADS)
Zhang, Yu; Zuo, Yan; Pan, Feng; Draayer, J. P.
2016-04-01
The spectral characteristics of the Lπ=0+ excited states in the interacting boson model are systematically investigated. It is found that various types of excited-state quantum phase transitions may widely occur in the model as functions of the excitation energy, which indicates that the phase diagram of the interacting boson model can be dynamically extended along the direction of the excitation energy. It has also been justified that the d -boson occupation probability ρ (E ) is qualified to be taken as the effective order parameter to identify these excited-state quantum phase transitions. In addition, the underlying relation between the excite-state quantum phase transition and the chaotic dynamics is also stated.
Modelling Absorbent Phenomena of Absorbent Structure
NASA Astrophysics Data System (ADS)
Sayeb, S.; Ladhari, N.; Ben Hassen, M.; Sakli, F.
Absorption, retention and strike through time, as evaluating criteria of absorbent structures quality were studied. Determination of influent parameters on these criteria were realized by using the design method of experimental sets. In this study, the studied parameters are: Super absorbent polymer (SAP)/fluff ratio, compression and the porosity of the non woven used as a cover stock. Absorption capacity and retention are mostly influenced by SAP/fluff ratio. However, strike through time is affected by compression. Thus, a modelling of these characteristics in function of the important parameter was established.
Robust Light State by Quantum Phase Transition in Non-Hermitian Optical Materials
NASA Astrophysics Data System (ADS)
Zhao, Han; Longhi, Stefano; Feng, Liang
2015-11-01
Robust light transport is the heart of optical information processing, leading to the search for robust light states by topological engineering of material properties. Here, it is shown that quantum phase transition, rather than topology, can be strategically exploited to design a novel robust light state. We consider an interface between parity-time (PT) symmetric media with different quantum phases and use complex Berry phase to reveal the associated quantum phase transition and topological nature. While the system possesses the same topological order within different quantum phases, phase transition from PT symmetry to PT breaking across the interface in the synthetic non-Hermitian metamaterial system facilitates novel interface states, which are robust against a variety of gain/loss perturbations and topological impurities and disorder. The discovery of the robust light state by quantum phase transition may promise fault-tolerant light transport in optical communications and computing.
Robust Light State by Quantum Phase Transition in Non-Hermitian Optical Materials
Zhao, Han; Longhi, Stefano; Feng, Liang
2015-01-01
Robust light transport is the heart of optical information processing, leading to the search for robust light states by topological engineering of material properties. Here, it is shown that quantum phase transition, rather than topology, can be strategically exploited to design a novel robust light state. We consider an interface between parity-time (PT) symmetric media with different quantum phases and use complex Berry phase to reveal the associated quantum phase transition and topological nature. While the system possesses the same topological order within different quantum phases, phase transition from PT symmetry to PT breaking across the interface in the synthetic non-Hermitian metamaterial system facilitates novel interface states, which are robust against a variety of gain/loss perturbations and topological impurities and disorder. The discovery of the robust light state by quantum phase transition may promise fault-tolerant light transport in optical communications and computing. PMID:26592765
Methods for absorbing neutrons
Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.
2012-07-24
A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.
Externally tuned vibration absorber
Vincent, Ronald J.
1987-09-22
A vibration absorber unit or units are mounted on the exterior housing of a hydraulic drive system of the type that is powered from a pressure wave generated, e.g., by a Stirling engine. The hydraulic drive system employs a piston which is hydraulically driven to oscillate in a direction perpendicular to the axis of the hydraulic drive system. The vibration absorbers each include a spring or other resilient member having one side affixed to the housing and another side to which an absorber mass is affixed. In a preferred embodiment, a pair of vibration absorbers is employed, each absorber being formed of a pair of leaf spring assemblies, between which the absorber mass is suspended.
Li, Linsen; Chen-Wiegart, Yu-chen Karen; Wang, Jiajun; Gao, Peng; Ding, Qi; Yu, Young-Sang; Wang, Feng; Cabana, Jordi; Wang, Jun; Jin, Song
2015-04-20
In situ techniques with high temporal, spatial and chemical resolution are key to understand ubiquitous solid-state phase transformations, which are crucial to many technological applications. Hard X-ray spectro-imaging can visualize electrochemically driven phase transformations but demands considerably large samples with strong absorption signal so far. Here we show a conceptually new data analysis method to enable operando visualization of mechanistically relevant weakly absorbing samples at the nanoscale and study electrochemical reaction dynamics of iron fluoride, a promising high-capacity conversion cathode material. In two specially designed samples with distinctive microstructure and porosity, we observe homogeneous phase transformations during both discharge andmore » charge, faster and more complete Li-storage occurring in porous polycrystalline iron fluoride, and further, incomplete charge reaction following a pathway different from conventional belief. In conclusion, these mechanistic insights provide guidelines for designing better conversion cathode materials to realize the promise of high-capacity lithium-ion batteries.« less
Geometric phase in p -n junctions of helical edge states
NASA Astrophysics Data System (ADS)
Wadhawan, Disha; Mehta, Poonam; Das, Sourin
2016-02-01
The quantum spin Hall effect is endowed with topologically protected edge modes with a gapless Dirac spectrum. Applying a magnetic field locally along the edge leads to a gapped edge spectrum with the opposite parity for winding of spin texture for conduction and valence bands. Using Pancharatnam's prescription for the geometric phase it is shown that mismatch of this parity across a p -n junction, which could be engineered into the edge by electrical gate induced doping, leads to a phase dependence in the two-terminal conductance which is quantized to either zero or π . It is further shown that application of a nonuniform magnetic field across the junction could lead to a nonquantized value of this geometric phase which is tunable between zero and π . A current asymmetry measurement which is shown to be robust against electron-electron interactions is proposed to infer the appearance of this Pancharatnam's geometric phase in transport across such junctions.
NASA Technical Reports Server (NTRS)
Schroeder, K. G.; Petroff, I. K.
1980-01-01
Two prototype solid-state phased array systems concepts for potential use in the Solar Power Satellite are described. In both concepts, the beam is centered on the rectenna by means of phase conjugation of a pilot signal emanating from the ground. Also discussed is on-going solid-state amplifier development.
40 CFR 72.73 - State issuance of Phase II permits.
Code of Federal Regulations, 2014 CFR
2014-07-01
... (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.73 State issuance of Phase II permits... permit program under part 70 of this chapter and that has a State Acid Rain program accepted by the Administrator under § 72.71 shall be responsible for administering and enforcing Acid Rain permits effective...
40 CFR 72.73 - State issuance of Phase II permits.
Code of Federal Regulations, 2013 CFR
2013-07-01
... (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.73 State issuance of Phase II permits... permit program under part 70 of this chapter and that has a State Acid Rain program accepted by the Administrator under § 72.71 shall be responsible for administering and enforcing Acid Rain permits effective...
40 CFR 72.73 - State issuance of Phase II permits.
Code of Federal Regulations, 2011 CFR
2011-07-01
... (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.73 State issuance of Phase II permits... permit program under part 70 of this chapter and that has a State Acid Rain program accepted by the Administrator under § 72.71 shall be responsible for administering and enforcing Acid Rain permits effective...
40 CFR 72.73 - State issuance of Phase II permits.
Code of Federal Regulations, 2012 CFR
2012-07-01
... (CONTINUED) PERMITS REGULATION Acid Rain Phase II Implementation § 72.73 State issuance of Phase II permits... permit program under part 70 of this chapter and that has a State Acid Rain program accepted by the Administrator under § 72.71 shall be responsible for administering and enforcing Acid Rain permits effective...
The Iron-Iron Carbide Phase Diagram: A Practical Guide to Some Descriptive Solid State Chemistry.
ERIC Educational Resources Information Center
Long, Gary J.; Leighly, H. P., Jr.
1982-01-01
Discusses the solid state chemistry of iron and steel in terms of the iron-iron carbide phase diagram. Suggests that this is an excellent way of introducing the phase diagram (equilibrium diagram) to undergraduate students while at the same time introducing the descriptive solid state chemistry of iron and steel. (Author/JN)
Advanced neutron absorber materials
Branagan, Daniel J.; Smolik, Galen R.
2000-01-01
A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.
Multispectral metamaterial absorber.
Grant, J; McCrindle, I J H; Li, C; Cumming, D R S
2014-03-01
We present the simulation, implementation, and measurement of a multispectral metamaterial absorber (MSMMA) and show that we can realize a simple absorber structure that operates in the mid-IR and terahertz (THz) bands. By embedding an IR metamaterial absorber layer into a standard THz metamaterial absorber stack, a narrowband resonance is induced at a wavelength of 4.3 μm. This resonance is in addition to the THz metamaterial absorption resonance at 109 μm (2.75 THz). We demonstrate the inherent scalability and versatility of our MSMMA by describing a second device whereby the MM-induced IR absorption peak frequency is tuned by varying the IR absorber geometry. Such a MSMMA could be coupled with a suitable sensor and formed into a focal plane array, enabling multispectral imaging. PMID:24690713
NASA Astrophysics Data System (ADS)
Abbasi, O.; Tavassoly, M. K.
2009-09-01
Considering the concept of " nonlinear coherent states", we will study the interference effects by introducing the " superposition of two classes of nonlinear coherent states" which are {π}/{2} out of phase. The formalism has then been applied to a few physical systems as "harmonious states", " SU(1,1) coherent states" and "the center of mass motion of trapped ion". Finally, the nonclassical properties such as sub-Poissonian statistics, quadrature squeezing, amplitude-squared squeezing and Wigner distribution function of the superposed states have been investigated, numerically. Especially, as we will observe the Wigner functions of the superposed states take negative values in phase space, while their original components do not.
Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases
Zhou, Tao; Gao, Yi; Wang, Z. D.
2014-01-01
We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally. PMID:24918901
Dynamical generation of phase-squeezed states in two-component Bose-Einstein condensates
Jin, G. R.; An, Y.; Yan, T.; Lu, Z. S.
2010-12-15
As an ''input'' state of a linear (Mach-Zehnder or Ramsey) interferometer, the phase-squeezed state proposed by Berry and Wiseman exhibits the best sensitivity approaching to the Heisenberg limit [Phys. Rev. Lett. 85, 5098 (2000)]. Similar with the Berry and Wiseman's state, we find that two kinds of phase-squeezed states can be generated dynamically with atomic Bose-Einstein condensates confined in a symmetric double-well potential, which shows squeezing along spin operator S{sub y} and antisqueezing along S{sub z}, leading to subshot-noise phase estimation.
The solid state structures of the high and low temperature phases of dimethylcadmium.
Hanke, Felix; Hindley, Sarah; Jones, Anthony C; Steiner, Alexander
2016-08-01
The solid state structure of dimethylcadmium, a classic organometallic compound with a long history, has remained elusive for almost a century. X-ray crystallography and density functional theory reveal similar phase behaviour as in dimethylzinc. The high temperature tetragonal phase, α-Me2Cd, exhibits two-dimensional disorder, while the low temperature monoclinic phase, β-Me2Cd, is ordered. Both phases contain linearly coordinated cadmium atoms. While the methyl groups are staggered in the α-phase, they are eclipsed in the β-phase. PMID:27457504
Interfacial Charge Transfer States in Condensed Phase Systems
NASA Astrophysics Data System (ADS)
Vandewal, Koen
2016-05-01
Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified.
Interfacial Charge Transfer States in Condensed Phase Systems.
Vandewal, Koen
2016-05-27
Intermolecular charge transfer (CT) states at the interface between electron-donating (D) and electron-accepting (A) materials in organic thin films are characterized by absorption and emission bands within the optical gap of the interfacing materials. CT states efficiently generate charge carriers for some D-A combinations, and others show high fluorescence quantum efficiencies. These properties are exploited in organic solar cells, photodetectors, and light-emitting diodes. This review summarizes experimental and theoretical work on the electronic structure and interfacial energy landscape at condensed matter D-A interfaces. Recent findings on photogeneration and recombination of free charge carriers via CT states are discussed, and relations between CT state properties and optoelectronic device parameters are clarified. PMID:26980308
Topological phases for bound states moving in a finite volume
Bour, Shahin; Koenig, Sebastian; Hammer, H.-W.; Lee, Dean; Meissner, Ulf-G.
2011-11-01
We show that bound states moving in a finite periodic volume have an energy correction which is topological in origin and universal in character. The topological volume corrections contain information about the number and mass of the constituents of the bound states. These results have broad applications to lattice calculations involving nucleons, nuclei, hadronic molecules, and cold atoms. We illustrate and verify the analytical results with several numerical lattice calculations.
Huang, Haitao; Li, Min; Liu, Pian; Jin, Lin; Wang, Hui; Shen, Deyuan
2016-06-15
Gold nanorods (GNRs) with an average aspect ratio of 15 were experimentally exploited as the 2 μm saturable absorber in a laser diode pumped Tm:YAG laser for the first time, to the best of our knowledge. Q-switched pulses with a maximum average output power of 380 mW, a minimum pulse width of 796 ns, and a pulse repetition rate of 77 kHz were achieved under the LD pump power of 6.2 W. Our results indicate that GNRs with a large aspect ratio are promising saturable absorbers in the 2 μm wavelength region. PMID:27304267
Ultrafast electronic relaxation of excited state vitamin B 12 in the gas phase
NASA Astrophysics Data System (ADS)
Shafizadeh, Niloufar; Poisson, Lionel; Soep, Benoıˆt
2008-06-01
The time evolution of electronically excited vitamin B 12 (cyanocobalamin) has been observed for the first time in the gas phase. It reveals an ultrafast decay to a state corresponding to metal excitation. This decay is interpreted as resulting from a ring to metal electron transfer. This opens the observation of the excited state of other complex biomimetic systems in the gas phase, the key to the characterisation of their complex evolution through excited electronic states.
NASA Astrophysics Data System (ADS)
Saukko, E.; Lambe, A. T.; Massoli, P.; Koop, T.; Wright, J. P.; Croasdale, D. R.; Pedernera, D. A.; Onasch, T. B.; Laaksonen, A.; Davidovits, P.; Worsnop, D. R.; Virtanen, A.
2012-04-01
There is mounting evidence showing that tropospheric secondary organic aerosol (SOA) may exist in a phase state other than liquid, namely semi-solid or solid amorphous. The solid or semi-solid, high viscosity material may have significantly higher lifetime in an oxidizing atmosphere than low viscosity liquid due to mass transfer limitations in the particle bulk. In this work we report a systematic study of the phase state of SOA particles produced by photo-oxidation of several volatile organic compound (VOC) precursors in a potential aerosol mass (PAM) flow tube reactor. The phase state of the particles was studied by their bounce behaviour upon impaction on a polished steel plate in a low pressure impactor. The SOA oxidation level (O/C) was determined by an Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) The phase state for several types of SOA from different surrogate anthropogenic and biogenic precursors, produced at a wide range of oxidation conditions, were studied at a range of relative humidities. We report the solid or semi-solid phase state of SOA produced from cyclic and terpene precursors used in the study up to at least 50 % relative humidity. Furthermore, adding sulfur dioxide into the reaction chamber yielded liquefied particles, while particles formed from oxidation of pure organic precursor were solid or semi-solid. For a long-chain alkane precursor a liquid-like SOA at low oxidation level was produced, but upon increasing the oxidation level, the formed particles became more solid. While the bounce behaviour of the particles had no single explaining factor for all experiments, the precursor molar mass was seen to correlate with more solid phase at higher humidities in cases with cyclic or terpene precursor.
Internal absorber solar collector
Sletten, Carlyle J.; Herskovitz, Sheldon B.; Holt, F. S.; Sletten, E. J.
1981-01-01
Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.
Discontinuous phase transition in an annealed multi-state majority-vote model
NASA Astrophysics Data System (ADS)
Li, Guofeng; Chen, Hanshuang; Huang, Feng; Shen, Chuansheng
2016-07-01
In this paper, we generalize the original majority-vote (MV) model with noise from two states to arbitrary q states, where q is an integer no less than two. The main emphasis is paid to the comparison on the nature of phase transitions between the two-state MV (MV2) model and the three-state MV (MV3) model. By extensive Monte Carlo simulation and mean-field analysis, we find that the MV3 model undergoes a discontinuous order-disorder phase transition, in contrast to a continuous phase transition in the MV2 model. A central feature of such a discontinuous transition is a strong hysteresis behavior as noise intensity goes forward and backward. Within the hysteresis region, the disordered phase and ordered phase are coexisting.
Metal shearing energy absorber
NASA Technical Reports Server (NTRS)
Fay, R. J.; Wittrock, E. P. (Inventor)
1973-01-01
A metal shearing energy absorber is described. The absorber is composed of a flat thin strip of metal which is pulled through a slot in a cutter member of a metal, harder than the metal of the strip. The slot's length, in the direction perpendicular to the pull direction, is less than the strip's width so that as the strip is pulled through the slot, its edges are sheared off, thereby absorbing some of the pulling energy. In one embodiment the cutter member is a flat plate of steel, while in another embodiment the cutter member is U-shaped with the slot at its base.
NASA Technical Reports Server (NTRS)
Marsh, H. E., Jr.; Wallace, C. J.
1973-01-01
The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.
Amplitude-phase coupling drives chimera states in globally coupled laser networks
NASA Astrophysics Data System (ADS)
Böhm, Fabian; Zakharova, Anna; Schöll, Eckehard; Lüdge, Kathy
2015-04-01
For a globally coupled network of semiconductor lasers with delayed optical feedback, we demonstrate the existence of chimera states. The domains of coherence and incoherence that are typical for chimera states are found to exist for the amplitude, phase, and inversion of the coupled lasers. These chimera states defy several of the previously established existence criteria. While chimera states in phase oscillators generally demand nonlocal coupling, large system sizes, and specially prepared initial conditions, we find chimera states that are stable for global coupling in a network of only four coupled lasers for random initial conditions. The existence is linked to a regime of multistability between the synchronous steady state and asynchronous periodic solutions. We show that amplitude-phase coupling, a concept common in different fields, is necessary for the formation of the chimera states.
1982-05-17
The State of Illinois has applied for Interim Authorization of its hazardous waste program under Subtitle C of the Resource Conservation and Recovery Act of 1976, as amended (RCRA) and EPA guidelines for the approval of State hazardous waste programs (40 CFR Part 123, Subpart F). USEPA has reviewed the Illinois hazardous waste program and has determined that the Illinois hazardous waste program is substantially equivalent to the Federal program. USEPA is hereby granting Phase I Interim Authorization to Illinois to operate a hazardous waste program in lieu of Phase I of the Federal hazardous waste program in its jurisdiction. PMID:10278121
Loss resilience for two-qubit state transmission using distributed phase sensitive amplification
Dailey, James; Agarwal, Anjali; Toliver, Paul; Peters, Nicholas A.
2015-11-12
We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA.
Loss resilience for two-qubit state transmission using distributed phase sensitive amplification
Dailey, James M.; Agarwal, Anjali; Toliver, Paul; Peters, Nicholas A.
2015-01-01
We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA. PMID:26559465
Loss resilience for two-qubit state transmission using distributed phase sensitive amplification.
Dailey, James M; Agarwal, Anjali; Toliver, Paul; Peters, Nicholas A
2015-01-01
We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA. PMID:26559465
Loss resilience for two-qubit state transmission using distributed phase sensitive amplification
NASA Astrophysics Data System (ADS)
Dailey, James M.; Agarwal, Anjali; Toliver, Paul; Peters, Nicholas A.
2015-11-01
We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA.
Phase diagram of quantum critical system via local convertibility of ground state
Liu, Si-Yuan; Quan, Quan; Chen, Jin-Jun; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2016-01-01
We investigate the relationship between two kinds of ground-state local convertibility and quantum phase transitions in XY model. The local operations and classical communications (LOCC) convertibility is examined by the majorization relations and the entanglement-assisted local operations and classical communications (ELOCC) via Rényi entropy interception. In the phase diagram of XY model, LOCC convertibility and ELOCC convertibility of ground-states are presented and compared. It is shown that different phases in the phase diagram of XY model can have different LOCC or ELOCC convertibility, which can be used to detect the quantum phase transition. This study will enlighten extensive studies of quantum phase transitions from the perspective of local convertibility, e.g., finite-temperature phase transitions and other quantum many-body models. PMID:27381284
Phase diagram of quantum critical system via local convertibility of ground state
NASA Astrophysics Data System (ADS)
Liu, Si-Yuan; Quan, Quan; Chen, Jin-Jun; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2016-07-01
We investigate the relationship between two kinds of ground-state local convertibility and quantum phase transitions in XY model. The local operations and classical communications (LOCC) convertibility is examined by the majorization relations and the entanglement-assisted local operations and classical communications (ELOCC) via Rényi entropy interception. In the phase diagram of XY model, LOCC convertibility and ELOCC convertibility of ground-states are presented and compared. It is shown that different phases in the phase diagram of XY model can have different LOCC or ELOCC convertibility, which can be used to detect the quantum phase transition. This study will enlighten extensive studies of quantum phase transitions from the perspective of local convertibility, e.g., finite-temperature phase transitions and other quantum many-body models.
Phase diagram of quantum critical system via local convertibility of ground state.
Liu, Si-Yuan; Quan, Quan; Chen, Jin-Jun; Zhang, Yu-Ran; Yang, Wen-Li; Fan, Heng
2016-01-01
We investigate the relationship between two kinds of ground-state local convertibility and quantum phase transitions in XY model. The local operations and classical communications (LOCC) convertibility is examined by the majorization relations and the entanglement-assisted local operations and classical communications (ELOCC) via Rényi entropy interception. In the phase diagram of XY model, LOCC convertibility and ELOCC convertibility of ground-states are presented and compared. It is shown that different phases in the phase diagram of XY model can have different LOCC or ELOCC convertibility, which can be used to detect the quantum phase transition. This study will enlighten extensive studies of quantum phase transitions from the perspective of local convertibility, e.g., finite-temperature phase transitions and other quantum many-body models. PMID:27381284
Semiclassical States Associated with Isotropic Submanifolds of Phase Space
NASA Astrophysics Data System (ADS)
Guillemin, V.; Uribe, A.; Wang, Z.
2016-05-01
We define classes of quantum states associated with isotropic submanifolds of cotangent bundles. The classes are stable under the action of semiclassical pseudo-differential operators and covariant under the action of semiclassical Fourier integral operators. We develop a symbol calculus for them; the symbols are symplectic spinors. We outline various applications.
On coherent-state representations of quantum mechanics: Wave mechanics in phase space
NASA Astrophysics Data System (ADS)
Møller, Klaus B.; Jørgensen, Thomas G.; Torres-Vega, Gabino
1997-05-01
In this article we argue that the state-vector phase-space representation recently proposed by Torres-Vega and co-workers [introduced in J. Chem. Phys. 98, 3103 (1993)] coincides with the totality of coherent-state representations for the Heisenberg-Weyl group. This fact leads to ambiguities when one wants to solve the stationary Schrödinger equation in phase space and we devise two schemes for the removal of these ambiguities. The physical interpretation of the phase-space wave functions is discussed and a procedure for computing expectation values as integrals over phase space is presented. Our formal points are illustrated by two examples.
Lemasson, Elise; Bertin, Sophie; Hennig, Philippe; Boiteux, Hélène; Lesellier, Eric; West, Caroline
2015-08-21
Supercritical fluid chromatography (SFC) is a very useful tool in the purpose of impurity profiling of drug candidates, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. The purpose of the present work is to develop a method for chemical purity assessment. The first part, presented here, focuses on mobile phase selection to ensure adequate elution and detection of drug-like molecules, while the second part focuses on stationary phase selection for optimal separation and orthogonality. The use of additives in the carbon dioxide - solvent mobile phase in SFC is now commonplace, and enables in particular to increase the number of eluted compounds and to improve peak shapes. The objective of this first part was to test different additives (acids, bases, salts and water) for their chromatographic performance assessed in gradient elution with a diode-array detector, but also for the mass responses obtained with a single-quadrupole mass detector, equipped with an electrospray ionization source (Waters ACQUITY QDa). In this project, we used a selection of one hundred and sixty compounds issued from Servier Research Laboratories to screen a set of columns and additives in SFC with a Waters ACQUITY UPC(2) system. The selected columns were all high-performance columns (1.7-1.8μm with totally porous particles or 2.6-2.7μm with superficially porous particles) with a variety of stationary phase chemistries. Initially, eight additives dissolved in the methanol co-solvent were tested on a UPC(2) ACQUITY UPC(2) HSS C18 SB column. A Derringer desirability function was used to classify the additives according to selected criteria: elution capability, peak shapes, UV baseline drift, and UV and mass responses (signal-to-noise ratios). Following these tests, the two best additives (ammonium acetate and ammonium hydroxide) were tested on a larger number of columns (10) where the two additives appeared
Entropy, chaos, and excited-state quantum phase transitions in the Dicke model.
Lóbez, C M; Relaño, A
2016-07-01
We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy. PMID:27575109
"Smart" Electromechanical Shock Absorber
NASA Technical Reports Server (NTRS)
Stokes, Lebarian; Glenn, Dean C.; Carroll, Monty B.
1989-01-01
Shock-absorbing apparatus includes electromechanical actuator and digital feedback control circuitry rather than springs and hydraulic damping as in conventional shock absorbers. Device not subject to leakage and requires little or no maintenance. Attenuator parameters adjusted in response to sensory feedback and predictive algorithms to obtain desired damping characteristic. Device programmed to decelerate slowly approaching vehicle or other large object according to prescribed damping characteristic.
NASA Astrophysics Data System (ADS)
González, J. O.; Shaji, S.; Avellaneda, D.; Castillo, G. A.; Das Roy, T. K.; Krishnan, B.
2014-09-01
Photovoltaic structures were prepared using AgSb(S x Se1- x )2 as absorber and CdS as window layer at various conditions via a hybrid technique of chemical bath deposition and thermal evaporation followed by heat treatments. Silver antimony sulfo selenide thin films [AgSb(S x Se1- x )2] were prepared by heating multilayers of sequentially deposited Sb2S3/Ag dipped in Na2SeSO3 solution, glass/Sb2S3/Ag/Se. For this, Sb2S3 thin films were deposited from a chemical bath containing SbCl3 and Na2S2O3. Then, Ag thin films were thermally evaporated on glass/Sb2S3, followed by selenization by dipping in an acidic solution of Na2SeSO3. The duration of dipping was varied as 3, 4 and 5 h. Two different heat treatments, one at 350 °C for 20 min in vacuum followed by a post-heat treatment at 325 °C for 2 h in Ar, and the other at 350 °C for 1 h in Ar, were applied to the multilayers of different configurations. X-ray diffraction results showed the formation of AgSb(S x Se1- x )2 thin films as the primary phase and AgSb(S,Se)2 and Sb2S3 as secondary phases. Morphology and elemental detection were done by scanning electron microscopy and energy dispersive X-ray analysis. X-ray photoelectron spectroscopic studies showed the depthwise composition of the films. Optical properties were determined by UV-vis-IR transmittance and reflection spectral analysis. AgSb(S x Se1- x )2 formed at different conditions was incorporated in PV structures glass/FTO/CdS/AgSb(S x Se1- x )2/C/Ag. Chemically deposited post-annealed CdS thin films of various thicknesses were used as window layer. J- V characteristics of the cells were measured under dark and AM1.5 illumination. Analysis of the J- V characteristics resulted in the best solar cell parameters of V oc = 520 mV, J sc = 9.70 mA cm-2, FF = 0.50 and η = 2.7 %.
NASA Astrophysics Data System (ADS)
Kuo, Yen-Kuang; Chang, Yi-An
2003-03-01
In a previous work [Appl. Phys. Lett. 65 , 3060 (1994) we experimentally demonstrated that passive ]Q switching of a 2017-nm, flashlamp-pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. We numerically investigate the optical performance of the Ho:YLF Q -switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with those obtained experimentally. With typical laser configuration, a Q -switched laser pulse of 35 mJ in 30 ns is obtained.
Ground states of stealthy hyperuniform potentials. II. Stacked-slider phases
NASA Astrophysics Data System (ADS)
Zhang, G.; Stillinger, F. H.; Torquato, S.
2015-08-01
Stealthy potentials, a family of long-range isotropic pair potentials, produce infinitely degenerate disordered ground states at high densities and crystalline ground states at low densities in d -dimensional Euclidean space Rd. In the previous paper in this series, we numerically studied the entropically favored ground states in the canonical ensemble in the zero-temperature limit across the first three Euclidean space dimensions. In this paper, we investigate using both numerical and theoretical techniques metastable stacked-slider phases, which are part of the ground-state manifold of stealthy potentials at densities in which crystal ground states are favored entropically. Our numerical results enable us to devise analytical models of this phase in two, three, and higher dimensions. Utilizing this model, we estimated the size of the feasible region in configuration space of the stacked-slider phase, finding it to be smaller than that of crystal structures in the infinite-system-size limit, which is consistent with our recent previous work. In two dimensions, we also determine exact expressions for the pair correlation function and structure factor of the analytical model of stacked-slider phases and analyze the connectedness of the ground-state manifold of stealthy potentials in this density regime. We demonstrate that stacked-slider phases are distinguishable states of matter; they are nonperiodic, statistically anisotropic structures that possess long-range orientational order but have zero shear modulus. We outline some possible future avenues of research to elucidate our understanding of this unusual phase of matter.
Ye Jinwu; Zhang Cunlin
2011-08-15
Recently, strong-coupling regimes of superconducting qubits or quantum dots inside a microwave circuit cavity and BEC atoms inside an optical cavity were achieved experimentally. The strong-coupling regimes in these systems were described by the Dicke model. Here, we solve the Dicke model by a 1/N expansion. In the normal state, we find a {radical}(N) behavior of the collective Rabi splitting. In the superradiant phase, we identify an important Berry phase term that has dramatic effects on both the ground state and the excitation spectra of the strongly interacting system. The single photon excitation spectrum has a low-energy quantum phase diffusion mode in imaginary time with a large spectral weight and also a high-energy optical mode with a low spectral weight. The photons are in a number squeezed state that may have wide applications in high sensitive measurements and quantum-information processing. Comparisons with exact diagonalization studies are made. Possible experimental schemes to realize the superradiant phase are briefly discussed.
Fingerprint of topological Andreev bound states in phase-dependent heat transport
NASA Astrophysics Data System (ADS)
Sothmann, Björn; Hankiewicz, Ewelina M.
2016-08-01
We demonstrate that phase-dependent heat currents through superconductor-topological insulator Josephson junctions provide a useful tool to probe the existence of topological Andreev bound states, even for multichannel surface states. We predict that in the tunneling regime topological Andreev bound states lead to a minimum of the thermal conductance for a phase difference ϕ =π , in clear contrast to a maximum of the thermal conductance at ϕ =π that occurs for trivial Andreev bound states in superconductor-normal-metal tunnel junctions. This opens up the possibility that phase-dependent heat transport can distinguish between topologically trivial and nontrivial 4 π modes. Furthermore, we propose a superconducting quantum interference device geometry where phase-dependent heat currents can be measured using available experimental technology.
Detecting critical state before phase transition of complex systems by hidden Markov model
NASA Astrophysics Data System (ADS)
Liu, Rui; Chen, Pei; Li, Yongjun; Chen, Luonan
Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e., before-transition state, pre-transition state, and after-transition state, which can be considered as three different Markov processes. Thus, based on this dynamical feature, we present a novel computational method, i.e., hidden Markov model (HMM), to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e., the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin, and HCV-induced dysplasia and hepatocellular carcinoma.
García, A Alonso; Grande, B Cancho; Gándara, J Simal
2004-10-29
An analytical method based on solid-phase extraction (SPE) and followed by liquid chromatographic separation and ultraviolet detection (HPLC-UV) is proposed for the determination of 10 phenolic compounds which participate on beer stability and sensory properties in alcohol-free beers. Acetonitrile was found to be the most appropriate solvent for the elution of polyphenolic compounds adsorbed on C18 cartridges. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (generally higher than 60%), repeatability (lower than 10%), linearity (r2 higher than 0.993) and limits of quantitation (ranging from 1 to 37 microg/L); no matrix effects were observed. The polyphenol content of different Spanish alcohol-free beers is presented. Five phenolic compounds such as protocatechuic, p-coumaric, ferulic, caffeic acids, and (+)-catechin were identified at levels lower than 10 mg/L. PMID:15553142
Density and Phase State of a Confined Nonpolar Fluid.
Kienle, Daniel F; Kuhl, Tonya L
2016-07-15
Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers. PMID:27472123
Density and Phase State of a Confined Nonpolar Fluid
NASA Astrophysics Data System (ADS)
Kienle, Daniel F.; Kuhl, Tonya L.
2016-07-01
Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers.
Phase transitions of the q-state Potts model on multiply-laced Sierpinski gaskets
NASA Astrophysics Data System (ADS)
Tian, Liang; Ma, Hui; Guo, Wenan; Tang, Lei-Han
2013-05-01
We present an exact solution of the q-state Potts model on a class of generalized Sierpinski fractal lattices. The model is shown to possess an ordered phase at low temperatures and a continuous transition to the high temperature disordered phase at any q ≥ 1. Multicriticality is observed in the presence of a symmetry-breaking field. Exact renormalization group analysis yields the phase diagram of the model and a complete set of critical exponents at various transitions.
Simplified formula for mean cycle-slip time of phase-locked loops with steady-state phase error.
NASA Technical Reports Server (NTRS)
Tausworthe, R. C.
1972-01-01
Previous work shows that the mean time from lock to a slipped cycle of a phase-locked loop is given by a certain double integral. Accurate numerical evaluation of this formula for the second-order loop is extremely vexing because the difference between exponentially large quantities is involved. The presented article demonstrates a method in which a much-reduced precision program can be used to obtain the mean first-cycle slip time for a loop of arbitrary degree tracking at a specified SNR and steady-state phase error. It also presents a simple approximate formula that is asymptotically tight at higher loop SNR.
One-Dimensional Three-State Quantum Walk with Single-Point Phase Defects
NASA Astrophysics Data System (ADS)
Xu, Yong-Zhen; Guo, Gong-De; Lin, Song
2016-09-01
In this paper, we study a three-state quantum walk with a phase defect at a designated position. The coin operator is a parametrization of the eigenvectors of the Grover matrix. We numerically investigate the properties of the proposed model via the position probability distribution, the position standard deviation, and the time-averaged probability at the designated position. It is shown that the localization effect can be governed by the phase defect's position and strength, coin parameter and initial state.
Phase states of a 2D easy-plane ferromagnet with strong inclined anisotropy
Fridman, Yu. A. Klevets, F. N.; Gorelikov, G. A.; Meleshko, A. G.
2012-12-15
We investigate the spin states of a 2D film exhibiting easy-axis anisotropy and a strong single-ion inclined anisotropy whose axis forms a certain angle with the normal to the film surface. Such a system may have an angular ferromagnetic phase, a spatially inhomogeneous state, and a quadrupole phase, whose realization depends substantially on the inclined anisotropy and the orientation of the wavevector in the film plane.
SESAME 96171, a three-phase equation of state for CeO2
Chisolm, Eric D.; Day, Christy M.
2014-06-25
We describe an equation of state (EOS) for cerium (IV) oxide, CeO_{2}, that includes two solid phases and the liquid. The models and parameters used to calculate the EOS are presented in detail, and we compare with data for both crystal phases and ambient melt. We discuss complications that arise when making multiphase EOS.
On the Finiteness of Collisions and Phase-Locked States for the Kuramoto Model
NASA Astrophysics Data System (ADS)
Ha, Seung-Yeal; Kim, Hwa Kil; Ryoo, Sang Woo
2016-04-01
Synchronization phenomenon is ubiquitous in our complex systems, and many phenomenological models have been proposed and studied analytically and numerically. Among them, the Kuramoto model serves as a prototype model for the phase synchronization of weakly coupled oscillators. In this paper, we study the finiteness of collisions (crossings) among Kuramoto oscillators in the relaxation process toward the phase-locked states and the total number of phase-locked states with positive (Kuramoto) order parameters. For identical oscillators, it is well known that collisions between distinct oscillators cannot occur in finite-time, and we show that there are only a finite number of phase-locked states with positive order parameters. However, for non-identical oscillators, oscillators with different natural frequencies can cross each other in their relaxation process, and estimating the total number of phase-locked states is a nontrivial matter. We show that, for the non-identical case, asymptotic phase-locking is equivalent to the finiteness of collisions, and the total number of phase-locked states with positive order parameters is bounded above by 2^N , where N is the number of oscillators.
On the Finiteness of Collisions and Phase-Locked States for the Kuramoto Model
NASA Astrophysics Data System (ADS)
Ha, Seung-Yeal; Kim, Hwa Kil; Ryoo, Sang Woo
2016-06-01
Synchronization phenomenon is ubiquitous in our complex systems, and many phenomenological models have been proposed and studied analytically and numerically. Among them, the Kuramoto model serves as a prototype model for the phase synchronization of weakly coupled oscillators. In this paper, we study the finiteness of collisions (crossings) among Kuramoto oscillators in the relaxation process toward the phase-locked states and the total number of phase-locked states with positive (Kuramoto) order parameters. For identical oscillators, it is well known that collisions between distinct oscillators cannot occur in finite-time, and we show that there are only a finite number of phase-locked states with positive order parameters. However, for non-identical oscillators, oscillators with different natural frequencies can cross each other in their relaxation process, and estimating the total number of phase-locked states is a nontrivial matter. We show that, for the non-identical case, asymptotic phase-locking is equivalent to the finiteness of collisions, and the total number of phase-locked states with positive order parameters is bounded above by 2^N, where N is the number of oscillators.
Role of phase composition for electronic states in CH3NH3PbI3 prepared from CH3NH3I/PbCl2 solution
NASA Astrophysics Data System (ADS)
Naikaew, Atittaya; Prajongtat, Pongthep; Lux-Steiner, Martha Ch.; Arunchaiya, Marisa; Dittrich, Thomas
2015-06-01
Modulated surface photovoltage (SPV) spectra have been correlated with the phase composition in layers of CH3NH3PbI3 (MAPbI3) prepared from MAI and PbCl2 and annealed at 100 °C. Depending on the annealing time, different compositions of MAPbI3, MAPbCl3, MACl, PbI2, and an un-identified phase were found. It has been demonstrated that evaporation of MAI and HI is crucial for the development of electronic states in MAPbI3 and that only the appearance and evolution of the phase PbI2 has an influence on electronic states in MAPbI3. With ongoing annealing, (i) a transition from p- to n-type doping was observed with the appearance of PbI2, (ii) shallow acceptor states were distinguished and disappeared in n-type doped MAPbI3, and (iii) a minimum of the SPV response related to deep defect states was found at the transition from p- to n-type doping. The results are discussed with respect to the further development of highly efficient and stable MAPbI3 absorbers for solar cells.
NASA Astrophysics Data System (ADS)
Kong, Desheng; Wang, Siming; Chen, Chinping
2008-07-01
The magnetization ground states (MGSs) for a nanosized Co hollow sphere, with the outer radius, R <50 nm, have been studied numerically by micromagnetic simulation using object oriented micromagnetic framework (OOMMF). In addition to the originally known single domain and vortex-curling states, a three dimensional "onion" state with a corresponding analytical expression is proposed and confirmed as one of the ground states. Two phase diagrams, one for a single crystalline and the other for a polycrystalline nanosphere, are obtained for the three MGSs. The result reveals that the magnetic anisotropy has a significant effect on the phase line in the diagrams. The finite temperature effect and the blocking properties of the nanosphere for the magnetization reversal are discussed.
The in-phase states of Josephson junctions stacks as attractors
Hristov, I.; Dimova, S.; Hristova, R.
2014-11-12
The aim of this investigation is to show that the coherent, in-phase states of intrinsic Josephson junctions stacks are attractors of the stacks' states when the applied external magnetic field h{sub e} and the external current γ vary within certain domains. Mathematically the problem is to find the solutions of the system of perturbed sine-Gordon equations for fixed other parameters and zero or random initial conditions. We determine the region in the plane (h{sub e}, γ), where the in-phase states are attractors of the stack's states for arbitrary initial perturbations. This is important, because the in-phase states are required for achieving terahertz radiation from the Josephson stacks.
Fang, Guozhen; Min, Guang; He, Jinxing; Zhang, Chao; Qian, Kun; Wang, Shuo
2009-04-22
A matrix solid-phase dispersion extraction (MSPDE) method was developed to extract 31 pesticides from agriculture samples using multiwalled carbon nanotubes (MWCNTs) as adsorbent prior to gas chromatography-mass spectrometry (GC-MS) determination. The comparisons of MWCNTs with C(18) and diatomite were studied in the MSPD procedure. The results showed that the extracts obtained by using MWCNTs were cleaner than those obtained by using C(18) and diatomite. Using the developed method, recoveries ranged from 74.2 to 104.2% with relative standard deviations (RSD) ranging from 3.1 to 8.8% for the apple matrix, and 71.5-113.3% with RSD ranging from 3.2 to 9.7% for the potato matrix. The limits of detection (LODs), calculated as 3 times the background noise, ranged from 0.1 to 3.1 microg kg(-1) for the apple matrix and 0.1 to 4.0 mug kg(-1) for the potato matrix. The proposed MSPDE method was used to analyze real samples obtained in a local market, the results were approximation to those obtained using accelerated solvent extraction (ASE) method, and prometryn, isocarbophos and methidathion were detected at levels below the maximum residue limits (MRLs) allowed by the Chinese Government. PMID:19326860
Comparison of time/phase lags in the hard state and plateau state of GRS 1915+105
Pahari, Mayukh; Yadav, J. S.; Neilsen, Joseph; Misra, Ranjeev; Uttley, Phil
2013-12-01
We investigate the complex behavior of energy- and frequency-dependent time/phase lags in the plateau state and the radio-quiet hard (χ) state of GRS 1915+105. In our timing analysis, we find that when the source is faint in the radio, quasi-periodic oscillations (QPOs) are observed above 2 Hz and typically exhibit soft lags (soft photons lag hard photons), whereas QPOs in the radio-bright plateau state are found below 2.2 Hz and consistently show hard lags. The phase lag at the QPO frequency is strongly anti-correlated with that frequency, changing sign at 2.2 Hz. However, the phase lag at the frequency of the first harmonic is positive and nearly independent of that frequency at ∼0.172 rad, regardless of the radio emission. The lag energy dependence at the first harmonic is also independent of radio flux. However, the lags at the QPO frequency are negative at all energies during the radio-quiet state, but lags at the QPO frequency during the plateau state are positive at all energies and show a 'reflection-type' evolution of the lag energy spectra with respect to the radio-quiet state. The lag energy dependence is roughly logarithmic, but there is some evidence for a break around 4-6 keV. Finally, the Fourier-frequency-dependent phase lag spectra are fairly flat during the plateau state, but increase from negative to positive during the radio-quiet state. We discuss the implications of our results in light of some generic models.
Phase boundary of spin-polarized-current state of electrons in bilayer graphene
NASA Astrophysics Data System (ADS)
Yan, Xin-Zhong; Ma, Yinfeng; Ting, C. S.
2016-06-01
Using a four-band Hamiltonian, we study the phase boundary of spin-polarized-current state (SPCS) of interacting electrons in bilayer graphene. The model of spin-polarized-current state has previously been shown to resolve a number of experimental puzzles in bilayer graphene. The phase boundaries of the SPCS with and without the external voltage between the two layers are obtained in this work. An unusual phase boundary where there are two transition temperatures for a given carrier concentration is found at finite external voltage. The physics of this phenomenon is explained.
Bilayer quantum Hall phase transitions and the orbifold non-Abelian fractional quantum Hall states
Barkeshli, Maissam; Wen Xiaogang
2011-09-15
We study continuous quantum phase transitions that can occur in bilayer fractional quantum Hall (FQH) systems as the interlayer tunneling and interlayer repulsion are tuned. We introduce a slave-particle gauge theory description of a series of continuous transitions from the (ppq) Abelian bilayer states to a set of non-Abelian FQH states, which we dub orbifold FQH states, of which the Z{sub 4} parafermion (Read-Rezayi) state is a special case. This provides an example in which Z{sub 2} electron fractionalization leads to non-Abelian topological phases. The naive ''ideal'' wave functions and ideal Hamiltonians associated with these orbifold states do not in general correspond to incompressible phases but, instead, lie at a nearby critical point. We discuss this unusual situation from the perspective of the pattern-of-zeros/vertex algebra frameworks and discuss implications for the conceptual foundations of these approaches. Due to the proximity in the phase diagram of these non-Abelian states to the (ppq) bilayer states, they may be experimentally relevant, both as candidates for describing the plateaus in single-layer systems at filling fractions 8/3 and 12/5 and as a way to tune to non-Abelian states in double-layer or wide quantum wells.
Geometric quantum phase for displaced states for a particle with an induced electric dipole moment
NASA Astrophysics Data System (ADS)
Lemos de Melo, J.; Bakke, K.; Furtado, C.
2016-07-01
Basing on the analogue Landau levels for a neutral particle possessing an induced electric dipole moment, we show that displaced states can be built in the presence of electric and magnetic fields. Besides, the Berry phase associated with these displaced quantum states is obtained by performing an adiabatic cyclic evolution in series of paths in parameter space.
NASA Technical Reports Server (NTRS)
Han, D.; Kim, Y. S.; Noz, Marilyn E.
1990-01-01
It is shown that the basic symmetry of two-mode squeezed states is governed by the group SP(4) in the Wigner phase space which is locally isomorphic to the (3 + 2)-dimensional Lorentz group. This symmetry, in the Schroedinger picture, appears as Dirac's two-oscillator representation of O(3,2). It is shown that the SU(2) and SU(1,1) interferometers exhibit the symmetry of this higher-dimensional Lorentz group. The mathematics of two-mode squeezed states is shown to be applicable to other branches of physics including thermally excited states in statistical mechanics and relativistic extended hadrons in the quark model.
State estimation of voltage and phase-shift transformer tap settings
Teixeira, P.A.; Brammer, S.R.; Rutz, W.L. ); Merritt, W.C.; Salmonsen, J.L. )
1992-08-01
Traditionally, state estimation algorithms have treated each transformer tap setting (voltage transformer turns ratio or phase-shift transformer angle) as a fixed parameter of the network, even though the real-time measurement may be in error or non-existent. In this paper, a new transformer tap estimation technique is presented which incorporates the function directly into the state estimation algorithm. The procedure provides for turns ratio and phase angle measurements and treats each transformer tap setting as an independent state variable. Test results for an actual 300-bus network demonstrate the tap estimation capability.
Exploring the phase space of multiple states in highly turbulent Taylor-Couette flow
NASA Astrophysics Data System (ADS)
van der Veen, Roeland C. A.; Huisman, Sander G.; Dung, On-Yu; Tang, Ho L.; Sun, Chao; Lohse, Detlef
2016-06-01
We investigate the existence of multiple turbulent states in highly turbulent Taylor-Couette flow in the range of Ta =1011 to 9 ×1012 by measuring the global torques and the local velocities while probing the phase space spanned by the rotation rates of the inner and outer cylinders. The multiple states are found to be very robust and are expected to persist beyond Ta =1013 . The rotation ratio is the parameter that most strongly controls the transitions between the flow states; the transitional values only weakly depend on the Taylor number. However, complex paths in the phase space are necessary to unlock the full region of multiple states. By mapping the flow structures for various rotation ratios in a Taylor-Couette setup with an equal radius ratio but a larger aspect ratio than before, multiple states are again observed. Here they are characterized by even richer roll structure phenomena, including an antisymmetrical roll state.
The steady-state phase distribution of the motor switch complex model of Halobacterium salinarum.
del Rosario, Ricardo C H; Diener, Francine; Diener, Marc; Oesterhelt, Dieter
2009-12-01
Steady-state analysis is performed on the kinetic model for the switch complex of the flagellar motor of Halobacterium salinarum (Nutsch et al.). The existence and uniqueness of a positive steady-state of the system is established and it is demonstrated why the steady-state is centered around the competent phase, a state of the motor in which it is able to respond to light stimuli. It is also demonstrated why the steady-state shifts to the refractory phase when the steady-state value of the response regulator CheYP increases. This work is one aspect of modeling in systems biology wherein the mathematical properties of a model are established. PMID:19857501
Multiple-layer Radiation Absorber
NASA Astrophysics Data System (ADS)
Baker, Robert M. L.; Baker, Bonnie Sue
A structure is discussed for absorbing incident radiation, either electromagnetic (EM) or sound. Such a surface structure is needed, for example, in a highly sensitive high-frequency gravitational wave or HFGW detector such as the Li-Baker. The multi-layer absorber, which is discussed, is constructed with metamaterial [MM] layer or layers on top. This MM is configured for a specific EM or sound radiation frequency band, which absorbs incident EM or sound radiation without reflection. Below these top MM layers is a substrate of conventional EM-radiation absorbing or acoustical absorbing reflective material, such as an array of pyramidal foam absorbers. Incident radiation is partially absorbed by the MM layer or layers, and then it is more absorbed by the lower absorbing and reflecting substrate. The remaining reflected radiation is even further absorbed by the MM layers on its "way out_ so that essentially all of the incident radiation is absorbed _ a nearly perfect black-body absorber. In a HFGW detector a substrate, such as foam absorbers, may outgas into a high vacuum and reduce the capability of the vacuum-producing equipment, however, the layers above this lowest substrate will seal the absorbing and reflecting substrate from any external vacuum. The layers also serve to seal the absorbing material against air or water flow past the surfaces of aircraft, watercraft or submarines. Other applications for such a multiple-level radiation absorber include stealth aircraft, missiles and submarines.
Circular polarization sensitive absorbers based on graphene
Yang, Kunpeng; Wang, Min; Pu, Mingbo; Wu, Xiaoyu; Gao, Hui; Hu, Chenggang; Luo, Xiangang
2016-01-01
It is well known that the polarization of a linearly polarized (LP) light would rotate after passing through a single layer graphene under the bias of a perpendicular magnetostatic field. Here we show that a corresponding phase shift could be expected for circularly polarized (CP) light, which can be engineered to design the circular polarization sensitive devices. We theoretically validate that an ultrathin graphene-based absorber with the thickness about λ/76 can be obtained, which shows efficient absorption >90% within incident angles of ±80°. The angle-independent phase shift produced by the graphene is responsible for the nearly omnidirectional absorber. Furthermore, a broadband absorber in frequencies ranging from 2.343 to 5.885 THz with absorption over 90% is designed by engineering the dispersion of graphene. PMID:27034257
Circular polarization sensitive absorbers based on graphene
NASA Astrophysics Data System (ADS)
Yang, Kunpeng; Wang, Min; Pu, Mingbo; Wu, Xiaoyu; Gao, Hui; Hu, Chenggang; Luo, Xiangang
2016-04-01
It is well known that the polarization of a linearly polarized (LP) light would rotate after passing through a single layer graphene under the bias of a perpendicular magnetostatic field. Here we show that a corresponding phase shift could be expected for circularly polarized (CP) light, which can be engineered to design the circular polarization sensitive devices. We theoretically validate that an ultrathin graphene-based absorber with the thickness about λ/76 can be obtained, which shows efficient absorption >90% within incident angles of ±80°. The angle-independent phase shift produced by the graphene is responsible for the nearly omnidirectional absorber. Furthermore, a broadband absorber in frequencies ranging from 2.343 to 5.885 THz with absorption over 90% is designed by engineering the dispersion of graphene.
Reconstruction of photon number conditioned states using phase randomized homodyne measurements
NASA Astrophysics Data System (ADS)
Chrzanowski, H. M.; Assad, S. M.; Bernu, J.; Hage, B.; Lund, A. P.; Ralph, T. C.; Lam, P. K.; Symul, T.
2013-05-01
We experimentally demonstrate the reconstruction of a photon number conditioned state without using a photon number discriminating detector. By using only phase randomized homodyne measurements, we reconstruct up to the three photon subtracted squeezed vacuum state. The reconstructed Wigner functions of these states show regions of pronounced negativity, signifying the non-classical nature of the reconstructed states. The techniques presented allow for complete characterization of the role of a conditional measurement on an ensemble of states, and might prove useful in systems where photon counting still proves technically challenging.
Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.
2004-05-04
The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.
Polarization transfer solid-state NMR for studying surfactant phase behavior.
Nowacka, Agnieszka; Mohr, Parveen Choudhary; Norrman, Jens; Martin, Rachel W; Topgaard, Daniel
2010-11-16
The phase behavior of amphiphiles, e.g., lipids and surfactants, at low water content is of great interest for many technical and pharmaceutical applications. When put in contact with air having a moderate relative humidity, amphiphiles often exhibit coexistence between solid and liquid crystalline phases, making their complete characterization difficult. This study describes a (13)C solid-state NMR technique for the investigation of amphiphile phase behavior in the water-poor regime. While the (13)C chemical shift is an indicator of molecular conformation, the (13)C signal intensities obtained with the CP and INEPT polarization transfer schemes yield information on molecular dynamics. A theoretical analysis incorporating the effect of molecular segment reorientation, with the correlation time τ(c) and order parameter S, shows that INEPT is most efficient for mobile segments with τ(c) < 0.01 μs and S < 0.05, while CP yields maximal signal for rigid segments with τ(c) > 10 μs and/or S > 0.5 under typical solid-state NMR experimental conditions. For liquid crystalline phases, where τ(c) < 0.01 μs and 0 < S < 0.3, the observed CP and INEPT intensities serve as a gauge of S. The combination of information on molecular conformation and dynamics permits facile phase diagram determination for systems with solid crystalline, solid amorphous, anisotropic liquid crystalline, and isotropic liquid (crystalline) phases as demonstrated by experiments on a series of reference systems with known phase structure. Three solid phases (anhydrous crystal, dihydrate, gel), two anisotropic liquid crystalline phases (normal hexagonal, lamellar), and two isotropic liquid crystalline phases (micellar cubic, bicontinuous cubic) are identified in the temperature-composition phase diagram of the cetyltrimethylammonium succinate/water system. Replacing the succinate counterion with DNA prevents the formation of phases other than hexagonal and leads to a general increase of τ(c). PMID
Exotic multi-quark states in the deconfined phase from gravity dual models
NASA Astrophysics Data System (ADS)
Burikham, P.; Chatrabhuti, A.; Hirunsirisawat, E.
2009-05-01
In the deconfined phase of quark-gluon plasma, it seems that most of the quarks, antiquarks and gluons should be effectively free in the absence of the linear confining potential. However, the remaining Coulomb-type potential between quarks in the plasma could still be sufficiently strong that certain bound states, notably of heavy quarks such as J/ψ are stable even in the deconfined plasma up to a certain temperature. Baryons can also exist in the deconfined phase provided that the density is sufficiently large. We study three kinds of exotic multi-quark bound states in the deconfined phase of quark-gluon plasma from gravity dual models in addition to the normal baryon. They are k-baryon, (N+bar k)-baryon and a bound state of j mesons which we call ``j-mesonance''. Binding energies and screening lengths of these exotic states are studied and are found to have similar properties to those of mesons and baryons at the leading order. Phase diagram for the exotic nuclear phases is subsequently studied in the Sakai-Sugimoto model. Even though the exotics are less stable than normal baryons, in the region of high chemical potential and low temperature, they are more stable thermodynamically than the vacuum and chiral-symmetric quark-gluon plasma phases (χS-QGP).
Optical manipulation of the Berry phase in a solid-state spin qubit
NASA Astrophysics Data System (ADS)
Yale, Christopher G.; Heremans, F. Joseph; Zhou, Brian B.; Auer, Adrian; Burkard, Guido; Awschalom, David D.
2016-03-01
Phase relations between quantum states represent a resource for storing and processing quantum information. Although quantum phases are commonly controlled dynamically by tuning energetic interactions, the use of geometric phases that accumulate during cyclic evolution may offer superior robustness to noise. To date, demonstrations of geometric phase in solid-state systems employ microwave fields that have limited spatial resolution. Here, we demonstrate an all-optical method to accumulate a geometric phase, the Berry phase, in an individual nitrogen-vacancy centre in diamond. Using stimulated Raman adiabatic passage controlled by diffraction-limited laser light, we loop the nitrogen-vacancy centre's spin around the Bloch sphere to enclose an arbitrary Berry phase. We investigate the limits of this control due to the loss of adiabaticity and decoherence, as well as its robustness to noise introduced into the experimental control parameters. These techniques set the foundation for optical geometric manipulation in photonic networks of solid-state qubits linked and controlled by light.
Topological phases protected by reflection symmetry and cross-cap states
NASA Astrophysics Data System (ADS)
Cho, Gil Young; Hsieh, Chang-Tse; Morimoto, Takahiro; Ryu, Shinsei
2015-05-01
Twisting symmetries provides an efficient method to diagnose symmetry-protected topological (SPT) phases. In this paper, edge theories of (2+1)-dimensional topological phases protected by reflection as well as other symmetries are studied by twisting reflection symmetry, which effectively puts the edge theories on an unoriented space-time, such as the Klein bottle. A key technical step taken in this paper is the use of the so-called cross-cap states, which encode entirely the unoriented nature of space-time, and can be obtained by rearranging the space-time geometry and exchanging the role of space and time coordinates. When the system is in a nontrivial SPT phase, we find that the corresponding cross-cap state is noninvariant under the action of the symmetries of the SPT phase, but acquires an anomalous phase. This anomalous phase, with a proper definition of a reference state, on which symmetry acts trivially, reproduces the known classification of (2+1)-dimensional bosonic and fermionic SPT phases protected by reflection symmetry, including in particular the Z8 classification of topological crystalline superconductors protected by reflection and time-reversal symmetries.
Role of the aerosol phase state in ammonia/amines exchange reactions.
Chan, Lap P; Chan, Chak K
2013-06-01
The exchange reaction of ammonia in (NH4)2SO4 with an amine and the corresponding reverse reaction of amines in aminium sulfates with ammonia were investigated using an electrodynamic balance coupled with a Raman spectrometer. The temporal changes in particle mass, chemical composition, and phase state were simultaneously monitored. When the salt particles were in an aqueous state at elevated relative humidities (RHs), the exchange of ammonia/amine vapors in the particle phase was reversible. The exchange rates of aqueous particles were in general higher than those of their corresponding solid counterparts. An aqueous phase was essential for the effective displacement of ammonia and amines. Aminium salts in different phase states and with different evaporation characteristics showed remarkably different reaction behaviors in ammonia vapor. The less compact amorphous aminium sulfate solids were more susceptible to ammonia exchange than the crystalline solids. The aminium salts in a liquid state exhibited substantial amine evaporation at <3% RH and formed acidic bisulfate. Under ammonia exposure, these acidic aminium droplets underwent both neutralization and displacement reactions. Stable solid salts containing ammonium, aminium, sulfate, and bisulfate were formed and hindered further reactions. The result suggests that ambient aminium sulfates may be acidic. Overall, the phase states of the ammonium and aminium salt particles crucially determine the heterogeneous reaction rates and final product properties and identities. PMID:23668831
Perfect terahertz absorber using fishnet based metafilm
Azad, Abul Kalam; Shchegolkov, Dmitry Yu; Chen, Houtong; Taylor, Antoinette; Smirnova, E I; O' Hara, John F
2009-01-01
We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.
The Variable Warm Absorber in Circinus X-1
NASA Astrophysics Data System (ADS)
Schulz, N. S.; Kallman, T. E.; Galloway, D. K.; Brandt, W. N.
2008-01-01
We observed Circinus X-1 twice during a newly reached low-flux phase near zero orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS) onboard Chandra. In both observations the source did not show the P Cygni lines we observed during the high-flux phases of the source in 2000 and 2001. During the prezero phase the source did not exhibit significant variability but did exhibit an emission-line spectrum rich in H- and He-like lines from high-Z elements such as Si, S, Ar, and Ca. The light curve in the postdip observation showed quiescent and flaring episodes. Only in these flaring episodes was the source luminosity significantly higher than observed during the prezero phase. We analyzed all high-resolution X-ray spectra by fitting photoionization and absorption models from the most recent version of the XSTAR code. The prezero-phase spectrum could be fully modeled with a very hot photoionized plasma with an ionization parameter of log ξ = 3.0, down from log ξ = 4.0 in the high-flux state. The ionization balances we measure from the spectra during the postzero-phase episodes are significantly different. Both episodes feature absorbers with variable high columns, ionization parameters, and luminosity. While cold absorption remains at levels quite similar to that observed in previous years, the new observations show unprecedented levels of variable warm absorption. The line emissivities also indicate that the observed low source luminosity is inconsistent with a static hot accretion disk corona (ADC), an effect that seems common to other near-edge-on ADC sources as well. We conclude that unless there exists some means of coronal heating other than X-rays, the true source luminosity is likely much higher, and we observe obscuration in analogy to the extragalactic Seyfert 2 sources. We discuss possible consequences and relate cold, lukewarm, warm, and hot absorbers to dynamic accretion scenarios.
NASA Astrophysics Data System (ADS)
Pedrosa, Inácio A.; Melo, Jilvan L.; Salatiel, Sadoque
2014-11-01
We present an alternative quantum treatment for a generalized mesoscopic RLC circuit with time-dependent resistance, inductance and capacitance. Taking advantage of the Lewis and Riesenfeld quantum invariant method and using quadratic invariants we obtain exact nonstationary Schrödinger states for this electromagnetic oscillation system. Afterwards, we construct coherent and squeezed states for the quantized RLC circuit and employ them to investigate some of the system's quantum properties, such as quantum fluctuations of the charge and the magnetic flux and the corresponding uncertainty product. In addition, we derive the geometric, dynamical and Berry phases for this nonstationary mesoscopic circuit. Finally we evaluate the dynamical and Berry phases for three special circuits. Surprisingly, we find identical expressions for the dynamical phase and the same formulae for the Berry's phase.
Design of multiband metamaterial absorber based on artificial magnetic conductor
NASA Astrophysics Data System (ADS)
Dang, Kezheng; He, Zijian; Li, Zhigang; Miao, Lei; Liu, Hao
2015-10-01
We present a general method to design multiband absorber by replacing the ground plane in a conventional metamaterial absorber with an artificial magnetic conductor. Due to its unique property of in-phase reflection at some specific frequency, the artificial magnetic conductor is used to introduce new absorption in the operation band. Meanwhile, out of the in-phase reflection band, the original absorbing capability of the absorber is reserved. To demonstrate it, we design a metamaterial absorber comprising three layers which are grids patterned resistive frequency selective surface, dielectric layer and the ground plane respectively. With an appropriate design, the absorber performs an absorbing peak at about 10 GHz. Then, we utilize a single band artificial magnetic conductor at 6.25 GHz and a dual-band one at 6.27 GHz and 8.17 GHz, which are both lossy and comprised of patches array varying in periodic size with a thickness of 0.6 mm, to replace the ground plane in the metamaterial absorber separately. The reflectivity of these multiband absorbers are simulated, and experiments are carried out later. Experimental results agree well with the simulations. All results verified that the method presented at the beginning is effective. The results show that additional absorptions exist at the frequencies where microwaves are nearly reflected in phase on the artificial magnetic conductor. Meanwhile the original absorbing capability of the metamaterial absorber has been preserved mostly. Based on the artificial magnetic conductor, the multiband absorber performs better with an increasing absorption bandwidth from 8.5 GHz to 10 GHz compared to the metamaterial absorber.
A First-Principles Multi-phase Equation of State of Carbon under Extreme Conditions
Correa, A A; Benedict, X L; Young, D A; Schwegler, E; Bonev, S A
2008-02-01
We describe the construction of a multi-phase equation of state for carbon at extreme pressures based on ab initio electronic structure calculations of two solid phases (diamond and BC8) and the liquid. Solid-phase free energies are built from knowledge of the cold curves and phonon calculations, together with direct ab initio molecular dynamics calculations of the equation of state, which are used to extract anharmonic corrections to the phonon free energy. The liquid free energy is constructed based on results from molecular dynamics calculations and constraints determined from previously calculated melting curves, assuming a simple solid-like free energy model. The resulting equation of state is extended to extreme densities and temperatures with a Thomas Fermi-based free energy model. Comparisons to available experimental results are discussed.
[Substrate phase state and time factor in variability of human fecal microbiota].
Bogdanova, E A; Nesvizhskiĭ, Iu V; Gerasimova, E V; Zverev, V V
2007-01-01
Effects of substrate phase state and time factor on variability of human fecal microbiota were studied. It was shown that microecological system of native feces was characterized by marked time-dependent variability. It is unstable and begins to destruct after 24 hours of cultivation. The most sensitive elements of the system were bifidobacteria and Escherichia coli. Change of phase state of biotope eliminated the effect of factor limiting the microecosystem development, which allowed species of obligate and transitory microflora to freely colonize the growth substrate and interact with each other. The mentioned facts demonstrate that fecal microbiota exists in the environment of excess of growth substrate, which colonization is limited by cluster structure of biotope of native feces. It was concluded that phase state of growth substrate and duration of cultivation are important factors determining the population variability of fecal microbiota. PMID:18277541
A solid-state PWM phase-shifter. [Pulse Width Modulation
Ooi, Boon Teck; Dai, Shu Zu; Galiana, F.D. )
1993-04-01
The solid-state, pulse width modulated (PWM) phase-shifter is based on gate-turn-off (GTO) thyristors or other valves with force commutation capabilities. Besides serving the phase-shifter function, it offers regulated control over 3 independent quantities: the real power passing through it and the VARs on both sides to which it is connected. The power transferred can be bidirectional and the VARs can be leading or lagging.
Multiple transition states and roaming in ion-molecule reactions: A phase space perspective
NASA Astrophysics Data System (ADS)
Mauguière, Frédéric A. L.; Collins, Peter; Ezra, Gregory S.; Farantos, Stavros C.; Wiggins, Stephen
2014-01-01
We provide a dynamical interpretation of the recently identified ‘roaming' mechanism for molecular dissociation reactions in terms of geometrical structures in phase space. These are NHIMs (Normally Hyperbolic Invariant Manifolds) and their stable/unstable manifolds that define transition states for ion-molecule association or dissociation reactions. The associated dividing surfaces rigorously define a roaming region of phase space, in which both reactive and non reactive trajectories can be trapped for arbitrarily long times.
Metasurface Broadband Solar Absorber
Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong
2016-02-01
Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributionsmore » to elucidate how the absorption occurs within the metasurface structure.« less
Metasurface Broadband Solar Absorber
Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong
2016-01-01
We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999
Metasurface Broadband Solar Absorber
NASA Astrophysics Data System (ADS)
Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong
2016-02-01
We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.
Metasurface Broadband Solar Absorber.
Azad, Abul K; Kort-Kamp, Wilton J M; Sykora, Milan; Weisse-Bernstein, Nina R; Luk, Ting S; Taylor, Antoinette J; Dalvit, Diego A R; Chen, Hou-Tong
2016-01-01
We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999
Cluster Mean-Field Approach to the Steady-State Phase Diagram of Dissipative Spin Systems
NASA Astrophysics Data System (ADS)
Jin, Jiasen; Biella, Alberto; Viyuela, Oscar; Mazza, Leonardo; Keeling, Jonathan; Fazio, Rosario; Rossini, Davide
2016-07-01
We show that short-range correlations have a dramatic impact on the steady-state phase diagram of quantum driven-dissipative systems. This effect, never observed in equilibrium, follows from the fact that ordering in the steady state is of dynamical origin, and is established only at very long times, whereas in thermodynamic equilibrium it arises from the properties of the (free) energy. To this end, by combining the cluster methods extensively used in equilibrium phase transitions to quantum trajectories and tensor-network techniques, we extend them to nonequilibrium phase transitions in dissipative many-body systems. We analyze in detail a model of spin-1 /2 on a lattice interacting through an X Y Z Hamiltonian, each of them coupled to an independent environment that induces incoherent spin flips. In the steady-state phase diagram derived from our cluster approach, the location of the phase boundaries and even its topology radically change, introducing reentrance of the paramagnetic phase as compared to the single-site mean field where correlations are neglected. Furthermore, a stability analysis of the cluster mean field indicates a susceptibility towards a possible incommensurate ordering, not present if short-range correlations are ignored.
Berry phase and its sign in quantum superposition states of thermal 87Rb atoms
NASA Astrophysics Data System (ADS)
Welte, S.; Basler, C.; Helm, H.
2014-02-01
We investigate the Berry phase in an ensemble of thermal 87Rb atoms which we prepare in a superposition state under conditions near and at electromagnetically induced transparency. The geometric phase is imprinted in the atoms by rotating the laboratory magnetic field. Phase-stabilized light fields permit us to monitor phase changes of the atomic sample in a Ramsey-type interferometer by instant probing of the absorptive response of the atoms as well as by monitoring the free-induction decay of the coherent superposition. The absolute sign of the phase is determined by reference to controllable phase shifts imposed by the experimenter. We prove that the geometric phase is independent of the rotational frequency of the magnetic field in the adiabatic regime, that the phase is additive in multiple rotations, and it is independent of the Landé factor of the atomic magnetic moment, as predicted in Berry's seminal paper. We show that the absolute sign of the phase encodes the sign of the observable angular momentum in relation to laboratory coordinates.
NASA Astrophysics Data System (ADS)
Mathur, S.
1999-08-01
As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".
NASA Technical Reports Server (NTRS)
Mathur, S.
1999-01-01
As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".
NASA Astrophysics Data System (ADS)
Lü, Xiaoling; Jiang, Liwei; Zheng, Yisong
2016-04-01
Graphene has intrinsic edge states localized at zigzag edge or lattice defect. Helical boundary states can also be established in such a two-dimensional carbon material at the boundary of topological insulator (TI) phase realized by the extrinsic Rashba spin-orbital coupling (SOC) in gated bilayer graphene. We theoretically investigate the interaction between these two kinds of edge (boundary) states when they coexist in a bilayer graphene. We find that this interaction gives rise to some very interesting results. In a zigzag edged nanoribbon of bilayer graphene, it is possible that the TI helical state does not localize at the TI phase boundary. Instead it moves to the nanoribbon edge even though the SOC is absent therein. In a bulk lattice of bilayer graphene embedded with two line defects, the numbers of helical state subbands at the two line defects are not equal to each other. In such a case, the backscattering lacking is still forbidden since the Kramers pairs are valley polarized.
Self-Injection Locking and Phase-Locked States in Microresonator-Based Optical Frequency Combs
NASA Astrophysics Data System (ADS)
Del'Haye, Pascal; Beha, Katja; Papp, Scott B.; Diddams, Scott A.
2014-01-01
Microresonator-based optical frequency combs have been a topic of extensive research during the last few years. Several theoretical models for the comb generation have been proposed; however, they do not comprehensively address experimental results that show a variety of independent comb generation mechanisms. Here, we present frequency-domain experiments that illuminate the transition of microcombs into phase-locked states, which show characteristics of injection locking between ensembles of comb modes. In addition, we demonstrate the existence of equidistant optical frequency combs that are phase stable but have nondeterministic phase relationships between individual comb modes.
Observation of a Topological and Parity-Dependent Phase of m=0 Spin States
Usami, Koji; Kozuma, Mikio
2007-10-05
A Ramsey interrogation scheme was used to measure the phase shift of laser-cooled {sup 87}Rb clock-transition pseudospins arising as a result of a reversal of a bias-magnetic field, i.e., B{yields}-B, during the interrogation. While no phase shift occurred when the reversal was sudden, the Ramsey fringes were shifted by a factor of {pi} when the reversal was adiabatic. We thus verified the prediction that the spin states |F,m=0> acquire a purely topological and parity-dependent phase factor of (-1){sup F} as a result of B{yields}-B.
Self-injection locking and phase-locked states in microresonator-based optical frequency combs.
Del'Haye, Pascal; Beha, Katja; Papp, Scott B; Diddams, Scott A
2014-01-31
Microresonator-based optical frequency combs have been a topic of extensive research during the last few years. Several theoretical models for the comb generation have been proposed; however, they do not comprehensively address experimental results that show a variety of independent comb generation mechanisms. Here, we present frequency-domain experiments that illuminate the transition of microcombs into phase-locked states, which show characteristics of injection locking between ensembles of comb modes. In addition, we demonstrate the existence of equidistant optical frequency combs that are phase stable but have nondeterministic phase relationships between individual comb modes. PMID:24580454
Solid-state dimer method for calculating solid-solid phase transitions
Xiao, Penghao; Henkelman, Graeme; Sheppard, Daniel; Rogal, Jutta
2014-05-07
The dimer method is a minimum mode following algorithm for finding saddle points on a potential energy surface of atomic systems. Here, the dimer method is extended to include the cell degrees of freedom for periodic solid-state systems. Using this method, reaction pathways of solid-solid phase transitions can be determined without having to specify the final state structure or reaction mechanism. Example calculations include concerted phase transitions between CdSe polymorphs and a nucleation and growth mechanism for the A15 to BCC transition in Mo.
M-ary-state phase-shift-keying discrimination below the homodyne limit
Becerra, F. E.; Fan, J.; Polyakov, S. V.; Migdall, A.; Baumgartner, G.; Goldhar, J.; Kosloski, J. T.
2011-12-15
We investigate a strategy for M-ary discrimination of nonorthogonal phase states with error rates below the homodyne limit. This strategy uses feed forward to update a reference field and signal nulling for the state discrimination. We experimentally analyze the receiver performance using postprocessing and a Bayesian strategy to emulate the feed-forward process. This analysis shows that for a moderate system detection efficiency, it is possible to surpass the homodyne error limit for quadrature phase-shift keying signals using feed forward.
Quantum phase transitions in composite matrix product states of one-dimensional spin-1/2 chains
NASA Astrophysics Data System (ADS)
Zhu, Jing-Min
2015-02-01
For matrix product states of one-dimensional spin-1/2 chains, we investigate the properties of quantum phase transition of the proposed composite system. We find that the system has three different ferromagnetic phases, one line of the two ferromagnetic phases coexisting equally describes the paramagnetic state, and the other two lines of two ferromagnetic phases coexisting equally describe the ferrimagnetic states, while the three phases coexisting equally point describes the ferromagnetic state. Whether on phase transition lines or at the phase transition point, the system is always in an isolated mediate-coupling state, the physical quantities are discontinuous and the system has long-range correlation and has long-range classical correlation and long-range quantum correlation. We believe that our work is helpful for comprehensively and profoundly understanding the quantum phase transitions, and of some certain guidance and enlightening on the classification and measure of quantum correlation of quantum many-body systems.
Lattice model theory of the equation of state covering the gas, liquid, and solid phases
NASA Technical Reports Server (NTRS)
Bonavito, N. L.; Tanaka, T.; Chan, E. M.; Horiguchi, T.; Foreman, J. C.
1975-01-01
The three stable states of matter and the corresponding phase transitions were obtained with a single model. Patterned after Lennard-Jones and Devonshires's theory, a simple cubic lattice model containing two fcc sublattices (alpha and beta) is adopted. The interatomic potential is taken to be the Lennard-Jones (6-12) potential. Employing the cluster variation method, the Weiss and the pair approximations on the lattice gas failed to give the correct phase diagrams. Hybrid approximations were devised to describe the lattice term in the free energy. A lattice vibration term corresponding to a free volume correction is included semi-phenomenologically. The combinations of the lattice part and the free volume part yield the three states and the proper phase diagrams. To determine the coexistence regions, the equalities of the pressure and Gibbs free energy per molecule of the coexisting phases were utilized. The ordered branch of the free energy gives rise to the solid phase while the disordered branch yields the gas and liquid phases. It is observed that the triple point and the critical point quantities, the phase diagrams and the coexistence regions plotted are in good agreement with the experimental values and graphs for argon.
On phase/current components of entropy/information descriptors of molecular states
NASA Astrophysics Data System (ADS)
Nalewajski, Roman F.
2014-10-01
Quantum-generalised descriptors of the information content of electronic states in molecules are proposed, in which non-classical (current) terms complement classical (probability) functionals of the ordinary information theory. The relation between densities of the familiar classical Fisher and Shannon information/entropy measures is applied to determine their non-classical complements. The quantum supplement of the classical Shannon entropy describes the average magnitude of the phase distribution, while the current term in the Fisher measure accounts for the gradient content of the state phase function. Illustrative applications of these quantum information concepts are presented and thermodynamical analogies are commented upon. The particle-density-constrained (vertical) and -unconstrained (horizontal) equilibria in molecules and their fragments are explored and the corresponding equilibrium 'thermodynamic' phases are determined. A separation of the density (modulus) and current (phase) factors of general many-electron states is effected using the Harriman-Zumbach-Maschke construction of antisymmetric states yielding the specified electron density. The phenomenological framework in spirit of the non-equilibrium thermodynamical description is proposed. It accounts for both the density and current degrees of freedom of molecular states. The associated entropy source in the information continuity equation is derived.
Topological phase transition and quantum spin Hall edge states of antimony few layers.
Kim, Sung Hwan; Jin, Kyung-Hwan; Park, Joonbum; Kim, Jun Sung; Jhi, Seung-Hoon; Yeom, Han Woong
2016-01-01
While two-dimensional (2D) topological insulators (TI's) initiated the field of topological materials, only very few materials were discovered to date and the direct access to their quantum spin Hall edge states has been challenging due to material issues. Here, we introduce a new 2D TI material, Sb few layer films. Electronic structures of ultrathin Sb islands grown on Bi2Te2Se are investigated by scanning tunneling microscopy. The maps of local density of states clearly identify robust edge electronic states over the thickness of three bilayers in clear contrast to thinner islands. This indicates that topological edge states emerge through a 2D topological phase transition predicted between three and four bilayer films in recent theory. The non-trivial phase transition and edge states are confirmed for epitaxial films by extensive density-functional-theory calculations. This work provides an important material platform to exploit microscopic aspects of the quantum spin Hall phase and its quantum phase transition. PMID:27624972
Coherent perfect absorber based on metamaterials
NASA Astrophysics Data System (ADS)
Nie, Guangyu; Shi, Quanchao; Zhu, Zheng; Shi, Jinhui
2014-11-01
We demonstrate selective coherent perfect absorption based on interaction between bilayered asymmetrically split rings (ASRs) metamaterials and a standing wave formed by two coherent counter propagating beams. The selective coherent perfect absorbers with high absorption have been achieved depending on the phase difference between two coherent beams. The selective coherent control absorbers can be well designed by changing the thickness of the dielectric layer and the asymmetry of the ASRs. The coherently controlled metamaterials provide an opportunity to realize selective multiband absorption and ultrafast information processing.
OSCEE fan exhaust bulk absorber treatment evaluation
NASA Technical Reports Server (NTRS)
Bloomer, H. E.; Samanich, N. E.
1980-01-01
The acoustic suppression capability of bulk absorber material designed for use in the fan exhaust duct walls of the quiet clean short haul experiment engine (OCSEE UTW) was evaluated. The acoustic suppression to the original design for the engine fan duct which consisted of phased single degree-of-freedom wall treatment was tested with a splitter and also with the splitter removed. Peak suppression was about as predicted with the bulk absorber configuration, however, the broadband characteristics were not attained. Post test inspection revealed surface oil contamination on the bulk material which could have caused the loss in bandwidth suppression.
Modification of electron states in CdTe absorber due to a buffer layer in CdTe/CdS solar cells
Fedorenko, Y. G. Major, J. D.; Pressman, A.; Phillips, L. J.; Durose, K.
2015-10-28
By application of the ac admittance spectroscopy method, the defect state energy distributions were determined in CdTe incorporated in thin film solar cell structures concluded on ZnO, ZnSe, and ZnS buffer layers. Together with the Mott-Schottky analysis, the results revealed a strong modification of the defect density of states and the concentration of the uncompensated acceptors as influenced by the choice of the buffer layer. In the solar cells formed on ZnSe and ZnS, the Fermi level and the energy position of the dominant deep trap levels were observed to shift closer to the midgap of CdTe, suggesting the mid-gap states may act as recombination centers and impact the open-circuit voltage and the fill factor of the solar cells. For the deeper states, the broadening parameter was observed to increase, indicating fluctuations of the charge on a microscopic scale. Such changes can be attributed to the grain-boundary strain and the modification of the charge trapped at the grain-boundary interface states in polycrystalline CdTe.
Passively Q-switched nd:YAG laser via a WS2 saturable absorber
NASA Astrophysics Data System (ADS)
Wang, Xi; Wang, Yonggang; Duan, Lina; Li, Lu; Sun, Hang
2016-05-01
In this work, we report a passively Q-switched Nd:YAG laser at 1064 nm by using WS2 solution as the saturable absorber (SA). The WS2 solution with different concentrations (0.25, 0.5, and 1 mg/ml) were fabricated by the liquid-phase-exfoliated method and injected into quartz cells. Such liquid absorbers have the virtues of adjustable optical absorption, high heat dissipation and non-contact damage. By inserting those WS2 solutions in the laser cavity, stable Q-switched laser operations were obtained. The corresponding pulse duration as short as 922 ns was obtained. The result shows that the WS2 material can be act as absorber for solid-state lasers.
Putting Phase Equilibria into Geodynamic Models: An Equation of State Approach (Invited)
NASA Astrophysics Data System (ADS)
Connolly, J.
2009-12-01
The use of free energy minimization codes to calculate the proportions and properties of minerals and consequently bulk rock properties is now commonplace in geophysical modeling. In effect such applications imply the existence of an equation of state, which is the optimized free energy as a function of its independent variables, for the rocks of interest. The essential feature of the equation of state is that all thermodynamic properties can be derived from it, a feature that requires that its derivatives are continuous. The equation of state may be calculated dynamically within the larger framework of a geodynamic code or it may be implemented statically via tables that are calculated prior to the solution of the geodynamic application. The virtues of static implementation is its extreme simplicity, computational efficiency, and that the finite resolution of the table assures that the equation of state is numerically differentiable for any choice of independent state variables. However, the memory required to store the requisite multidimensional tables may necessitate dynamic implementations for problems involving multi-component mass transfer, e.g., as in reactive melt transport. Paradoxically, the unlimited accuracy of dynamic solutions creates a potential numerical instability, the Stefan problem, for geodynamic governing equations formulated in terms of pressure and temperature. This instability arises because the derivatives of an equation of state for a polyphase aggregate as a function of pressure and temperature are singular at the conditions of a low order phase transformation. An equation of state as a function of specific entropy, specific volume and chemical composition eliminates this difficulty and, additionally, leads to a robust formulation of the energy and mass conservation equations. In this formulation, energy and mass conservation furnish evolution equations for entropy and volume and the equation of state serves as an update rule for
Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition.
Jaramillo, R; Feng, Yejun; Lang, J C; Islam, Z; Srajer, G; Littlewood, P B; McWhan, D B; Rosenbaum, T F
2009-05-21
Advances in solid-state and atomic physics are exposing the hidden relationships between conventional and exotic states of quantum matter. Prominent examples include the discovery of exotic superconductivity proximate to conventional spin and charge order, and the crossover from long-range phase order to preformed pairs achieved in gases of cold fermions and inferred for copper oxide superconductors. The unifying theme is that incompatible ground states can be connected by quantum phase transitions. Quantum fluctuations about the transition are manifestations of the competition between qualitatively distinct organizing principles, such as a long-wavelength density wave and a short-coherence-length condensate. They may even give rise to 'protected' phases, like fluctuation-mediated superconductivity that survives only in the vicinity of an antiferromagnetic quantum critical point. However, few model systems that demonstrate continuous quantum phase transitions have been identified, and the complex nature of many systems of interest hinders efforts to more fully understand correlations and fluctuations near a zero-temperature instability. Here we report the suppression of magnetism by hydrostatic pressure in elemental chromium, a simple cubic metal that demonstrates a subtle form of itinerant antiferromagnetism formally equivalent to the Bardeen-Cooper-Schrieffer (BCS) state in conventional superconductors. By directly measuring the associated charge order in a diamond anvil cell at low temperatures, we find a phase transition at pressures of approximately 10 GPa driven by fluctuations that destroy the BCS-like state but preserve the strong magnetic interaction between itinerant electrons and holes. Chromium is unique among stoichiometric magnetic metals studied so far in that the quantum phase transition is continuous, allowing experimental access to the quantum singularity and a direct probe of the competition between conventional and exotic order in a
Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transtion.
Jaramillo, R.; Feng, Y.; Lang, J. C.; Islam, Z.; Srajer, G.; Littlewood, P. B.; Mc Whan, D. B.; Rosenbaum, T. F.; Univ. of Chicago; Univ. of Cambridge; Massachusetts Innst. of Tech.
2009-05-21
Advances in solid-state and atomic physics are exposing the hidden relationships between conventional and exotic states of quantum matter. Prominent examples include the discovery of exotic superconductivity proximate to conventional spin and charge order, and the crossover from long-range phase order to preformed pairs achieved in gases of cold fermions and inferred for copper oxide superconductors. The unifying theme is that incompatible ground states can be connected by quantum phase transitions. Quantum fluctuations about the transition are manifestations of the competition between qualitatively distinct organizing principles, such as a long-wavelength density wave and a short-coherence-length condensate. They may even give rise to 'protected' phases, like fluctuation-mediated superconductivity that survives only in the vicinity of an antiferromagnetic quantum critical point. However, few model systems that demonstrate continuous quantum phase transitions have been identified, and the complex nature of many systems of interest hinders efforts to more fully understand correlations and fluctuations near a zero-temperature instability. Here we report the suppression of magnetism by hydrostatic pressure in elemental chromium, a simple cubic metal that demonstrates a subtle form of itinerant antiferromagnetism formally equivalent to the Bardeen-Cooper-Schrieffer (BCS) state in conventional superconductors. By directly measuring the associated charge order in a diamond anvil cell at low temperatures, we find a phase transition at pressures of 10 GPa driven by fluctuations that destroy the BCS-like state but preserve the strong magnetic interaction between itinerant electrons and holes. Chromium is unique among stoichiometric magnetic metals studied so far in that the quantum phase transition is continuous, allowing experimental access to the quantum singularity and a direct probe of the competition between conventional and exotic order in a theoretically tractable
Lim, Sunghyuk; Yu, Qinhong; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Ames, James B
2016-04-01
Cyanobacteriochromes (CBCRs) are cyanobacterial photosensory proteins with a tetrapyrrole (bilin) chromophore that belong to the phytochrome superfamily. Like phytochromes, CBCRs photoconvert between two photostates with distinct spectral properties. NpR6012g4 from Nostoc punctiforme is a model system for widespread CBCRs with conserved red/green photocycles. Atomic-level structural information for the photoproduct state in this subfamily is not known. Here, we report NMR backbone chemical shift assignments of the light-activated state of NpR6012g4 (BMRB no. 26577) as a first step toward determining its atomic resolution structure. PMID:26537963
A Dynamic Absorber With Active Vibration Control
NASA Astrophysics Data System (ADS)
Huang, S.-J.; Lian, R.-J.
1994-12-01
The design and construction of a dynamic absorber incorporating active vibration control is described. The absorber is a two-degrees-of-freedom spring — lumped mass system sliding on a guide pillar, with two internal vibration disturbance sources. Both the main mass and the secondary absorber mass are acted on by DC servo motors, respectively, to suppress the vibration amplitude. The state variable technique is used to model this dynamic system and a decoupling PID control method is used. First, the discrete time state space model is identified by using the commercial software MATLAB. Then the decoupling controller of this multi-input/multi-output system is derived from the identified model. Finally the results of some experiments are presented. The experimental results show that the system is effective in suppressing vibration. Also, the performance of this control strategy for position tracking control is evaluated based on experimental data.
A shock absorber model for structure-borne noise analyses
NASA Astrophysics Data System (ADS)
Benaziz, Marouane; Nacivet, Samuel; Thouverez, Fabrice
2015-08-01
Shock absorbers are often responsible for undesirable structure-borne noise in cars. The early numerical prediction of this noise in the automobile development process can save time and money and yet remains a challenge for industry. In this paper, a new approach to predicting shock absorber structure-borne noise is proposed; it consists in modelling the shock absorber and including the main nonlinear phenomena responsible for discontinuities in the response. The model set forth herein features: compressible fluid behaviour, nonlinear flow rate-pressure relations, valve mechanical equations and rubber mounts. The piston, base valve and complete shock absorber model are compared with experimental results. Sensitivity of the shock absorber response is evaluated and the most important parameters are classified. The response envelope is also computed. This shock absorber model is able to accurately reproduce local nonlinear phenomena and improves our state of knowledge on potential noise sources within the shock absorber.
A search for the ground state structure and the phase stability of tantalum pentoxide.
Pérez-Walton, S; Valencia-Balvín, C; Padilha, A C M; Dalpian, G M; Osorio-Guillén, J M
2016-01-27
Tantalum pentoxide (Ta2O5) is a wide-gap semiconductor that presents good catalytic and dielectric properties, conferring to this compound promising prospective use in a variety of technological applications. However, there is a lack of understanding regarding the relations among its crystalline phases, as some of them are not even completely characterized and there is currently no agreement about which models better explain the crystallographic data. Additionally, its phase diagram is unknown. In this work we performed first-principles density functional theory calculations to study the structural properties of the different phases and models of Ta2O5, the equation of state and the zone-centered vibrational frequencies. From our results, we conclude that the phases that are built up from only distorted octahedra instead of combinations with pentagonal and/or hexagonal bipyramids are energetically more favorable and dynamically stable. More importantly, this study establishes that, given the pressure range considered, the B-phase is the most favorable structure and there is no a crystallographic phase transition to another phase at high-pressure. Additionally, for the equilibrium volume of the B-phase and the λ-model, the description of the electronic structure and optical properties were performed using semi-local and hybrid functionals. PMID:26702713
A search for the ground state structure and the phase stability of tantalum pentoxide
NASA Astrophysics Data System (ADS)
Pérez-Walton, S.; Valencia-Balvín, C.; Padilha, A. C. M.; Dalpian, G. M.; Osorio-Guillén, J. M.
2016-01-01
Tantalum pentoxide (Ta2O5) is a wide-gap semiconductor that presents good catalytic and dielectric properties, conferring to this compound promising prospective use in a variety of technological applications. However, there is a lack of understanding regarding the relations among its crystalline phases, as some of them are not even completely characterized and there is currently no agreement about which models better explain the crystallographic data. Additionally, its phase diagram is unknown. In this work we performed first-principles density functional theory calculations to study the structural properties of the different phases and models of Ta2O5, the equation of state and the zone-centered vibrational frequencies. From our results, we conclude that the phases that are built up from only distorted octahedra instead of combinations with pentagonal and/or hexagonal bipyramids are energetically more favorable and dynamically stable. More importantly, this study establishes that, given the pressure range considered, the B-phase is the most favorable structure and there is no a crystallographic phase transition to another phase at high-pressure. Additionally, for the equilibrium volume of the B-phase and the λ-model, the description of the electronic structure and optical properties were performed using semi-local and hybrid functionals.
Absorber for terahertz radiation management
Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.
2015-12-08
A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.
Ising spin network states for loop quantum gravity: a toy model for phase transitions
NASA Astrophysics Data System (ADS)
Feller, Alexandre; Livine, Etera R.
2016-03-01
Non-perturbative approaches to quantum gravity call for a deep understanding of the emergence of geometry and locality from the quantum state of the gravitational field. Without background geometry, the notion of distance should emerge entirely from the correlations between the gravity fluctuations. In the context of loop quantum gravity, quantum states of geometry are defined as spin networks. These are graphs decorated with spin and intertwiners, which represent quantized excitations of areas and volumes of the space geometry. Here, we develop the condensed-matter point of view on extracting the physical and geometrical information from spin network states: we introduce new Ising spin network states, both in 2d on a square lattice and in 3d on a hexagonal lattice, whose correlations map onto the usual Ising model in statistical physics. We construct these states from the basic holonomy operators of loop gravity and derive a set of local Hamiltonian constraints that entirely characterize our states. We discuss their phase diagram and show how the distance can be reconstructed from the correlations in the various phases. Finally, we propose generalizations of these Ising states, which open the perspective to study the coarse-graining and dynamics of spin network states using well-known condensed-matter techniques and results.
NASA Astrophysics Data System (ADS)
Takada, K.; Tomioka, A.
2012-04-01
Liquid-phase laser processing, where the laser-irradiated target material is immersed in water for cooling, has been reported as a promising processing technique for thermally fragile organic materials. Although nanometer-sized particles have been reported to be obtained with the liquid-phase laser processing, the physical property did not change because quantum-mechanical size effect does not exhibit itself in the zero-radius Frenkel excitons. In the present study, we step further to use solution droplets as a target material, where organic molecules are molecularly dispersed in organic solvent and, therefore, expected to easily alter the conformation and the energy state upon laser irradiation. Small volume organic solvent is quickly evaporated upon laser irradiation, letting the bare organic molecule placed in water and rapidly cooled. To prevent the chemical decomposition of the target π-conjugated molecule, the specimen was resonantly irradiated by a ns-pulse green laser, not by a conventional UV laser. When the solid state spin-coat film made from MEH-PPV chloroform solution was used as a irradiation target immersed in water, resulting MEH-PPV particles showed similar photoluminescence (PL) like the PL of the spin-coat film and PL of the chloroform solution, including the 0→1, 0→2 vibrational transitions: this indicates that the energy levels were not modified from the spin-coat film. In comparison, when tiny droplets of MEH-PPV chloroform solution (orange color) were suspended in water, laser irradiation gave rise to yellow MEH-PPV particles which showed 550 nm and 530 nm PL (type B), blue-shifted from the spin-coat film PL 580 nm (type A), suggesting a successful phase transition of MEH-PPV polymer to type B. Further solution-phase laser processing left the type B state unchanged. The irreversible phase transition from type A to type B suggests that the type B ground state has lower energy than type A, which is consistent with the blue-shifted PL of
Temporal, latitude and altitude absorbed dose dependences
NASA Astrophysics Data System (ADS)
Stozhkov, Y.; Svirzhevsky, N.; Bazilevskaya, G.
The regular balloon measurements in the Earth's atmosphere are carried on at the Lebedev Physical Institute since 1957. The regular balloon flights have been made at the high latitude stations (near Murmansk - northern hemisphere and Mi ny -r Antarctica) and at the middle latitude (Moscow). Based on these long-term measurements as well as on the latitude data obtained in the several Soviet Antarctic expeditions the calculations of absorbed doses were fulfilled for altitudes of 10, 15, 20 and 30 km. The absorbed dose dependences on the geomagnetic cutoff rigidities and the phase of the 11-year solar cycle were found. The evaluation of the solar proton events and energetic electron precipitation contributions to the absorbed dose enhancements was made.
Corrosion resistant neutron absorbing coatings
Choi, Jor-Shan; Farmer, Joseph C.; Lee, Chuck K.; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor
2012-05-29
A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.
Corrosion resistant neutron absorbing coatings
Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor
2013-11-12
A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.
Materials research for passive solar systems: solid-state phase-change materials
Benson, D.K.; Webb, J.D.; Burrows, R.W.; McFadden, J.D.O.; Christensen, C.
1985-03-01
A set of solid-state phase-change materials is being evaluated for possible use in passive solar thermal energy storage systems. The most promising materials are organic solid solutions of pentaerythritol (C/sub 5/H/sub 12/O/sub 4/), pentaglycerinve (C/sub 5/H/sub 12/O/sub 3/), and neopentyl glycol (C/sub 5/H/sub 12/O/sub 2/). Solid solution mixtures of these compounds can be tailored so that they exhibit solid-to-solid phase transformations at any desired temperature betweeen 25/sup 0/C and 188/sup 0/C, and have latent heats of transformation between 20 and 70 cal/g. Transformation temperatures, specific heats, and latent heats of transformation have been measured for a number of these materials. Limited cyclic experiments suggest that the solid solutions are stable. These phase-change materials exhibit large amounts of undercooling; however, the addition of certain nucleating agents as particulate dispersions in the solid phase-change material greatly reduces this effect. Computer simulations suggest that the use of an optimized solid-state phase-change material in a Trombe wall could provide better performance than a concrete Trombe wall four times thicker and nine times heavier. Nevertheless, a higher cost of the phase-change materials (approx. =$0.70 per pound) is likely to limit their applicability in passive solar systems unless their performance can be significantly improved through further research.
Day Care Licensing Study Summary Report on Phase I: State and Local Day Care Licensing Requirements.
ERIC Educational Resources Information Center
Consulting Services Corp., Seattle, WA.
Phase I of the Day Care Licensing Study is presented. It includes a summary of findings, conclusions, and recommendations; two sections on day care regulations; a section on day care facilities; and a section on the climate for change. Appendices include: Methodology; Depts. of State Government Responsible for Licensing Day Care Facilities;…
Effects of phase states on reactions of secondary organic materials with chloride
NASA Astrophysics Data System (ADS)
Wang, B.; Laskin, A.; OBrien, R. E.; Kelly, S. T.; Shilling, J. E.; Moffet, R.; Gilles, M. K.
2014-12-01
Secondary organic materials (SOM) in atmospheric aerosols are often mixed with inorganic components. Condensed-phase SOM can exist in a liquid, semi-solid, or solid state at different temperatures and RH. We investigated the effects of phase states of SOM on the reactions of SOM from ozonolysis of limonene (LSOM) and α-pinene (PSOM) with NaCl using a set of complementary micro-spectroscopic analyses. SOM can react with NaCl and result in chloride depletion in the condensed phase, release of gaseous HCl, and formation of organic salts. The reactions driven by the high volatility of HCl are attributed to acid displacement by SOM acidic components. Similar reactions can take place in SOM/NaNO3 particles. Glass transition temperatures and viscosity of PSOM were estimated. The results show that the reaction depends on SOM composition, phase state and viscosity, mixing state, and reaction time. The release and potential recycling of HCl and HNO3 from reacted aerosol particles may have important implications for atmospheric chemistry. This reaction can modify particle physicochemical properties, such as the ability to form clouds, and thus may have important atmospheric implications.
Structural-phase states and wear resistance of surface formed on steel by surfacing
Kapralov, Evgenie V.; Raykov, Sergey V.; Vaschuk, Ekaterina S.; Budovskikh, Evgenie A. Gromov, Victor E.; Ivanov, Yuri F.
2014-11-14
Investigations of elementary and phase structure, state of defect structure and tribological characteristics of a surfacing, formed on a low carbon low-alloy steel by a welding method were carried out. It was revealed that a surfacing, formed on a steel surface is accompanied by the multilayer formation, and increases the wear resistance of the layer surfacing as determined.
Multiple-copy distillation and purification of phase-diffused squeezed states
Marek, Petr; Fiurasek, Jaromir; Hage, Boris; Franzen, Alexander; DiGugliemo, James; Schnabel, Roman
2007-11-15
We provide a detailed theoretical analysis of multiple-copy purification and distillation protocols for phase-diffused squeezed states of light. The standard iterative distillation protocol is generalized to a collective purification of an arbitrary number of N copies. We also derive a semianalytical expression for the asymptotic limit of the iterative distillation and purification protocol and discuss its properties.
Quantum displacement receiver for M-ary phase-shift-keyed coherent states
Izumi, Shuro; Takeoka, Masahiro; Fujiwara, Mikio; Sasaki, Masahide; Pozza, Nicola Dalla; Assalini, Antonio
2014-12-04
We propose quantum receivers for 3- and 4-ary phase-shift-keyed (PSK) coherent state signals to overcome the standard quantum limit (SQL). Our receiver, consisting of a displacement operation and on-off detectors with or without feedforward, provides an error probability performance beyond the SQL. We show feedforward operations can tolerate the requirement for the detector specifications.
Phase transitions in neutron star equation of state induced by the delta resonances matter
NASA Astrophysics Data System (ADS)
T, Oliveira J. C.; Rodrigues, H.; Duarte, S. B.
2016-04-01
In the present work we determine the equation of state and the population of baryons and leptons, and also we discuss the implication of changes in the baryon-meson coupling constants to the formation of delta matter in the stellar medium. And also in this work the phase transition is explored with respect to the domain of the delta-mesons coupling constants.
Hacking on decoy-state quantum key distribution system with partial phase randomization
NASA Astrophysics Data System (ADS)
Sun, Shi-Hai; Jiang, Mu-Sheng; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei
2014-04-01
Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum + weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states.
State diagram of magnetostatic coupling phase-locked spin-torque oscillators
Zhang, Mengwei; Wang, Longze; Wei, Dan; Gao, Kai-Zhong
2015-05-07
The state diagram of magnetostatic coupling phase-locked spin torque oscillator (STO) with perpendicular reference layer and planar field generation layer (FGL) is studied by the macrospin model and the micromagnetic model. The state diagrams of current densities are calculated under various external fields. The simulation shows that there are two phase-lock current density regions. In the phase-locked STOs in low current region I, the spin configuration of FGL is uniform; in high current region II, the spin configuration of FGL is highly nonuniform. In addition, the results with different STOs separation L{sub s} are compared, and the coupling between two STOs is largely decreased when L{sub s} is increased from 40 nm to 60 nm.
Hacking on decoy-state quantum key distribution system with partial phase randomization.
Sun, Shi-Hai; Jiang, Mu-Sheng; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei
2014-01-01
Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum + weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states. PMID:24755767
Friedel phase discontinuity and bound states in the continuum in quantum dot systems
NASA Astrophysics Data System (ADS)
Solís, B.; Ladrón de Guevara, M. L.; Orellana, P. A.
2008-06-01
In this Letter we study the Friedel phase of the electron transport in two different systems of quantum dots which exhibit bound states in the continuum (BIC). The Friedel phase jumps abruptly in the energies of the BICs, which is associated to the vanishing width of these states, as shown by Friedrich and Wintgen in [H. Friedrich, D. Wintgen, Phys. Rev. A 31 (1985) 3964]. This odd behavior of the Friedel phase has consequences in the charge through the Friedel sum rule. Namely, if the energy of the BIC drops under the Fermi energy the charge changes abruptly in a unity. We show that this behavior closely relates to discontinuities in the conductance predicted for interacting quantum dot systems.
Hacking on decoy-state quantum key distribution system with partial phase randomization
Sun, Shi-Hai; Jiang, Mu-Sheng; Ma, Xiang-Chun; Li, Chun-Yan; Liang, Lin-Mei
2014-01-01
Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum + weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states. PMID:24755767
Zhou, Rong; Tang, Pinghua; Chen, Yu; Chen, Shuqing; Zhao, Chujun; Zhang, Han; Wen, Shuangchun
2014-01-10
Nonlinear transmission parameters of monolayer graphene at 1645 nm were obtained. Based on the monolayer graphene saturable absorber, a 1532 nm LD pumped 1645 nm passively Q-switched Er:YAG laser was demonstrated. Under the pump power of 20.8 W, a 1645 nm Q-switched pulse with FWHM of 0.13 nm (without the use of etalon) and energy of 13.5 μJ per pulse can be obtained. To the best of our knowledge, this is the highest pulse energy for graphene-based passively Q-switched Er:YAG laseroperating at 1645 nm, suggesting the potentials of graphene materials for high-energy solid-state laser applications. PMID:24514058
Optimal active vibration absorber - Design and experimental results
NASA Technical Reports Server (NTRS)
Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.
1993-01-01
An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.
Optimal active vibration absorber: Design and experimental results
NASA Technical Reports Server (NTRS)
Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.
1992-01-01
An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.
Influence of particle-phase state on the hygroscopic behavior of mixed organic-inorganic aerosols
NASA Astrophysics Data System (ADS)
Hodas, N.; Zuend, A.; Mui, W.; Flagan, R. C.; Seinfeld, J. H.
2015-05-01
Recent work has demonstrated that organic and mixed organic-inorganic particles can exhibit multiple phase states depending on their chemical composition and on ambient conditions such as relative humidity (RH). To explore the extent to which water uptake varies with particle-phase behavior, hygroscopic growth factors (HGFs) of nine laboratory-generated, organic and organic-inorganic aerosol systems with physical states ranging from well-mixed liquids to phase-separated particles to viscous liquids or semi-solids were measured with the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe at RH values ranging from 40 to 90%. Water-uptake measurements were accompanied by HGF and RH-dependent thermodynamic equilibrium calculations using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model. In addition, AIOMFAC-predicted growth curves are compared to several simplified HGF modeling approaches: (1) representing particles as ideal, well-mixed liquids; (2) forcing a single phase but accounting for non-ideal interactions through activity coefficient calculations; and (3) a Zdanovskii-Stokes-Robinson-like calculation in which complete separation of the inorganic and organic components is assumed at all RH values, with water uptake treated separately in each of the individual phases. We observed variability in the characteristics of measured hygroscopic growth curves across aerosol systems with differing phase behaviors, with growth curves approaching smoother, more continuous water uptake with decreasing prevalence of liquid-liquid phase separation and increasing oxygen : carbon ratios of the organic aerosol components. We also observed indirect evidence for the dehydration-induced formation of highly viscous semi-solid phases and for kinetic limitations to the crystallization of ammonium sulfate at low RH for sucrose-containing particles. AIOMFAC-predicted growth curves are generally in good agreement with the HGF
Influence of particle phase state on the hygroscopic behavior of mixed organic-inorganic aerosols
NASA Astrophysics Data System (ADS)
Hodas, N.; Zuend, A.; Mui, W.; Flagan, R. C.; Seinfeld, J. H.
2014-12-01
Recent work has demonstrated that organic and mixed organic-inorganic particles can exhibit multiple phase states depending on their chemical composition and on ambient conditions such as relative humidity (RH). To explore the extent to which water uptake varies with particle phase behavior, hygroscopic growth factors (HGFs) of nine laboratory-generated, organic and organic-inorganic aerosol systems with physical states ranging from well-mixed liquids, to phase-separated particles, to viscous liquids or semi-solids were measured with the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe at RH values ranging from 40-90%. Water-uptake measurements were accompanied by HGF and RH-dependent thermodynamic equilibrium calculations using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model. In addition, AIOMFAC-predicted growth curves are compared to several simplified HGF modeling approaches: (1) representing particles as ideal, well-mixed liquids, (2) forcing a single phase, but accounting for non-ideal interactions through activity coefficient calculations, and (3) a Zdanovskii-Stokes-Robinson-like calculation in which complete separation between the inorganic and organic components is assumed at all RH values, with water-uptake treated separately in each of the individual phases. We observed variability in the characteristics of measured hygroscopic growth curves across aerosol systems with differing phase behaviors, with growth curves approaching smoother, more continuous water uptake with decreasing prevalence of liquid-liquid phase separation and increasing oxygen : carbon ratios of the organic aerosol components. We also observed indirect evidence for the dehydration-induced formation of highly viscous semi-solid phases and for kinetic limitations to the crystallization of ammonium sulfate at low RH for sucrose-containing particles. AIOMFAC-predicted growth curves are generally in good agreement with the HGF
Solar radiation absorbing material
Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.
1977-01-01
Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.
Powell, W R
1974-10-01
A simple, economical absorber utilizing a new principle of operation to achieve very low reradiation losses while generating temperatures limited by material properties of quartz is described. Its performance is analyzed and indicates approximately 90% thermal efficiency and 73% conversion efficiency for an earth based unit with moderately concentrated (~tenfold) sunlight incident. It is consequently compatible with the most economic of concentrator mirrors (stamped) or mirrors deployable in space. Space applications are particularly attractive, as temperatures significantly below 300 K are possible and permit even higher conversion efficiency. PMID:20134700
NASA Technical Reports Server (NTRS)
Benet, James
1993-01-01
The final report describes the work performed from 9 Jun. 1992 to 31 Jul. 1993 on the NASA Satellite Communications Application Research (SCAR) Phase 2 program, Efficient High Power, Solid State Amplifier for EHF Communications. The purpose of the program was to demonstrate the feasibility of high-efficiency, high-power, EHF solid state amplifiers that are smaller, lighter, more efficient, and less costly than existing traveling wave tube (TWT) amplifiers by combining the output power from up to several hundred solid state amplifiers using a unique orthomode spatial power combiner (OSPC).
The quantum state vector in phase space and Gabor's windowed Fourier transform
NASA Astrophysics Data System (ADS)
Bracken, A. J.; Watson, P.
2010-10-01
Representations of quantum state vectors by complex phase space amplitudes, complementing the description of the density operator by the Wigner function, have been defined by applying the Weyl-Wigner transform to dyadic operators, linear in the state vector and anti-linear in a fixed 'window state vector'. Here aspects of this construction are explored, and a connection is established with Gabor's 'windowed Fourier transform'. The amplitudes that arise for simple quantum states from various choices of windows are presented as illustrations. Generalized Bargmann representations of the state vector appear as special cases, associated with Gaussian windows. For every choice of window, amplitudes lie in a corresponding linear subspace of square-integrable functions on phase space. A generalized Born interpretation of amplitudes is described, with both the Wigner function and a generalized Husimi function appearing as quantities linear in an amplitude and anti-linear in its complex conjugate. Schrödinger's time-dependent and time-independent equations are represented on phase space amplitudes, and their solutions described in simple cases.
Zero-temperature equation of state and phase diagram of repulsive fermionic mixtures
NASA Astrophysics Data System (ADS)
Fratini, E.; Pilati, S.
2014-08-01
We compute the zero-temperature equation of state of a mixture of two fermionic atomic species with repulsive interspecies interactions using second-order perturbation theory. We vary the interaction strength, the population, and the mass imbalance, and we analyze the competition between different states: homogeneous, partially separated, and fully separated. The canonical phase diagrams are determined for various mass ratios, including the experimentally relevant case of the Li6-K40 mixture. We find substantial differences with respect to the equal-mass case: phase separation occurs at weaker interaction strength, and the partially separated state can be stable even in the limit of a large majority of heavy atoms. We highlight the effects due to correlations by making comparisons with previous mean-field results.
Magnetic anisotropy in Shiba bound states across a quantum phase transition
NASA Astrophysics Data System (ADS)
Hatter, Nino; Heinrich, Benjamin W.; Ruby, Michael; Pascual, Jose I.; Franke, Katharina J.
2015-11-01
The exchange coupling between magnetic adsorbates and a superconducting substrate leads to Shiba states inside the superconducting energy gap and a Kondo resonance outside the gap. The exchange coupling strength determines whether the quantum many-body ground state is a Kondo singlet or a singlet of the paired superconducting quasiparticles. Here we use scanning tunnelling spectroscopy to identify the different quantum ground states of manganese phthalocyanine on Pb(111). We observe Shiba states, which are split into triplets by magnetocrystalline anisotropy. Their characteristic spectral weight yields an unambiguous proof of the nature of the quantum ground state. Our results provide experimental insights into the phase diagram of a magnetic impurity on a superconducting host and shine light on the effects induced by magnetic anisotropy on many-body interactions.
Magnetic anisotropy in Shiba bound states across a quantum phase transition
Hatter, Nino; Heinrich, Benjamin W.; Ruby, Michael; Pascual, Jose I.; Franke, Katharina J.
2015-01-01
The exchange coupling between magnetic adsorbates and a superconducting substrate leads to Shiba states inside the superconducting energy gap and a Kondo resonance outside the gap. The exchange coupling strength determines whether the quantum many-body ground state is a Kondo singlet or a singlet of the paired superconducting quasiparticles. Here we use scanning tunnelling spectroscopy to identify the different quantum ground states of manganese phthalocyanine on Pb(111). We observe Shiba states, which are split into triplets by magnetocrystalline anisotropy. Their characteristic spectral weight yields an unambiguous proof of the nature of the quantum ground state. Our results provide experimental insights into the phase diagram of a magnetic impurity on a superconducting host and shine light on the effects induced by magnetic anisotropy on many-body interactions. PMID:26603561
S1 and S2 Excited States of Gas-Phase Schiff-Base Retinal Chromophores
NASA Astrophysics Data System (ADS)
Nielsen, I. B.; Lammich, L.; Andersen, L. H.
2006-01-01
Photoabsorption studies of 11-cis and all-trans Schiff-base retinal chromophore cations in the gas phase have been performed at the electrostatic ion storage ring in Aarhus. A broad absorption band due to the optically allowed excitation to the first electronically excited singlet state (S1) is observed at around 600 nm. A second “dark” excited state (S2) just below 400 nm is reported for the first time. It is located ˜1.2eV above S1 for both chromophores. The S2 state was not visible in a solution measurement where only one highly blueshifted absorption band corresponding to the first excited state was visible. Knowledge of the position of the excited states in retinal is essential for the understanding of the fast photoisomerization in, for example, visual pigments.
Chimera states in systems of nonlocal nonidentical phase-coupled oscillators
NASA Astrophysics Data System (ADS)
Xie, Jianbo; Kao, Hsien-Ching; Knobloch, Edgar
2015-03-01
Chimera states consisting of domains of coherently and incoherently oscillating nonlocally coupled phase oscillators in systems with spatial inhomogeneity are studied. The inhomogeneity is introduced through the dependence of the oscillator frequency on its location. Two types of spatial inhomogeneity, localized and spatially periodic, are considered and their effects on the existence and properties of multicluster and traveling chimera states are explored. The inhomogeneity is found to break up splay states, to pin the chimera states to specific locations, and to trap traveling chimeras. Many of these states can be studied by constructing an evolution equation for a complex order parameter. Solutions of this equation are in good agreement with the results of numerical simulations.
Liquid Cryogen Absorber for MICE
Baynham, D.E.; Bish, P.; Bradshaw, T.W.; Cummings, M.A.; Green,M.A.; Ishimoto, S.; Ivaniouchenkov, I.; Lau, W.; Yang, S.Q.; Zisman, M.S.
2005-08-20
The Muon Ionization Cooling Experiment (MICE) will test ionization cooling of muons. In order to have effective ionization cooling, one must use an absorber that is made from a low-z material. The most effective low z materials for ionization cooling are hydrogen, helium, lithium hydride, lithium and beryllium, in that order. In order to measure the effect of material on cooling, several absorber materials must be used. This report describes a liquid-hydrogen absorber that is within a pair of superconducting focusing solenoids. The absorber must also be suitable for use with liquid helium. The following absorber components are discussed in this report; the absorber body, its heat exchanger, the hydrogen system, and the hydrogen safety. Absorber cooling and the thin windows are not discussed here.
Phase diagram and the pseudogap state in a linear chiral homopolymer model
NASA Astrophysics Data System (ADS)
Sinelnikova, A.; Niemi, A. J.; Ulybyshev, M.
2015-09-01
The phase structure of a single self-interacting homopolymer chain is investigated in terms of a universal theoretical model, designed to describe the chain in the infrared limit of slow spatial variations. The effects of chirality are studied and compared with the influence of a short-range attractive interaction between monomers, at various ambient temperature values. In the high-temperature limit the homopolymer chain is in the self-avoiding random walk phase. At very low temperatures two different phases are possible: When short-range attractive interactions dominate over chirality, the chain collapses into a space-filling conformation. But when the attractive interactions weaken, there is a low-temperature unfolding transition and the chain becomes like a straight rod. Between the high- and low-temperature limits, several intermediate states are observed, including the θ regime and pseudogap state, which is a novel form of phase state in the context of polymer chains. Applications to polymers and proteins, in particular collagen, are suggested.
Phase diagram and the pseudogap state in a linear chiral homopolymer model.
Sinelnikova, A; Niemi, A J; Ulybyshev, M
2015-09-01
The phase structure of a single self-interacting homopolymer chain is investigated in terms of a universal theoretical model, designed to describe the chain in the infrared limit of slow spatial variations. The effects of chirality are studied and compared with the influence of a short-range attractive interaction between monomers, at various ambient temperature values. In the high-temperature limit the homopolymer chain is in the self-avoiding random walk phase. At very low temperatures two different phases are possible: When short-range attractive interactions dominate over chirality, the chain collapses into a space-filling conformation. But when the attractive interactions weaken, there is a low-temperature unfolding transition and the chain becomes like a straight rod. Between the high- and low-temperature limits, several intermediate states are observed, including the θ regime and pseudogap state, which is a novel form of phase state in the context of polymer chains. Applications to polymers and proteins, in particular collagen, are suggested. PMID:26465490
Topological states and phase transitions in Sb2Te3-GeTe multilayers
Nguyen, Thuy-Anh; Backes, Dirk; Singh, Angadjit; Mansell, Rhodri; Barnes, Crispin; Ritchie, David A.; Mussler, Gregor; Lanius, Martin; Grützmacher, Detlev; Narayan, Vijay
2016-01-01
Topological insulators (TIs) are bulk insulators with exotic ‘topologically protected’ surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb2Te3 and the band insulator GeTe, we provide experimental evidence of multiple topological modes in a single Sb2Te3-GeTe-Sb2Te3 structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb2Te3-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases. PMID:27291288
Topological states and phase transitions in Sb2Te3-GeTe multilayers.
Nguyen, Thuy-Anh; Backes, Dirk; Singh, Angadjit; Mansell, Rhodri; Barnes, Crispin; Ritchie, David A; Mussler, Gregor; Lanius, Martin; Grützmacher, Detlev; Narayan, Vijay
2016-01-01
Topological insulators (TIs) are bulk insulators with exotic 'topologically protected' surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb2Te3 and the band insulator GeTe, we provide experimental evidence of multiple topological modes in a single Sb2Te3-GeTe-Sb2Te3 structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb2Te3-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases. PMID:27291288
Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation
Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.
2006-11-21
Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.
Network simulation of steady-state two-phase flow in consolidated porous media
Constantinides, G.N.; Payatakes, A.C.
1996-02-01
Multiphase flow in porous media is a complex process encountered in many fields of practical engineering interest, such as oil recovery from reservoir rocks, aquifer pollution by liquid wastes and soil reconstitution, and agricultural irrigation. A computer-aided simulator of steady-state two-phase flow in consolidated porous media is developed. The porous medium is modeled as a 3-D pore network of suitably shaped and randomly sized unit cells of the constricted-tube type. The problem of two-phase flow is solved using the network approach. The wetting phase saturation, the viscosity ratio, the capillary number, and the probability of coalescence between two colliding ganglia are changed systematically, where as the geometrical and topological characteristics of the porous medium and wettability (dynamic contact angles) are kept constant. In the range of the parameter values investigated, the flow behavior observed is ganglion population dynamics (intrinsically unsteady, but giving a time-averaged steady state). The mean ganglion size and fraction of the nonwetting phase in the form of stranded ganglia are studied as functions of the main dimensionless parameters. Fractional flows and relative permeabilities are determined and correlated with flow phenomena at pore level. Effects of the wetting phase saturation, the viscosity ratio, the capillary number, and the coalescence factor on relative permeabilities are examined.
Topological states and phase transitions in Sb2Te3-GeTe multilayers
NASA Astrophysics Data System (ADS)
Nguyen, Thuy-Anh; Backes, Dirk; Singh, Angadjit; Mansell, Rhodri; Barnes, Crispin; Ritchie, David A.; Mussler, Gregor; Lanius, Martin; Grützmacher, Detlev; Narayan, Vijay
2016-06-01
Topological insulators (TIs) are bulk insulators with exotic ‘topologically protected’ surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb2Te3 and the band insulator GeTe, we provide experimental evidence of multiple topological modes in a single Sb2Te3-GeTe-Sb2Te3 structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb2Te3-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases.
Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation
NASA Astrophysics Data System (ADS)
Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.
2006-11-01
Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90°. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system—atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.
Magnetic properties of two-dimensional nanodots: Ground state and phase transition
Kasperski, Maciej; Puszkarski, Henryk; Hoang, Danh-Tai; Diep, H. T.
2013-12-15
We study the effect of perpendicular single-ion anisotropy, −As{sub z}{sup 2}, on the ground-state structure and finite-temperature properties of a two-dimensional magnetic nanodot in presence of a dipolar interaction of strength D. By a simulated annealing Monte Carlo method, we show that in the ground state a vortex core perpendicular to the nanodot plane emerges already in the range of moderate anisotropy values above a certain threshold level. In the giant-anisotropy regime the vortex structure is superseded by a stripe domain structure with stripes of alternate domains perpendicular to the surface of the sample. We have also observed an intermediate stage between the vortex and stripe structures, with satellite regions of tilted nonzero perpendicular magnetization around the core. At finite temperatures, at small A, we show by Monte Carlo simulations that there is a transition from the the in-plane vortex phase to the disordered phase characterized by a peak in the specific heat and the vanishing vortex order parameter. At stronger A, we observe a discontinuous transition with a large latent heat from the in-plane vortex phase to perpendicular stripe ordering phase before a total disordering at higher temperatures. In the regime of perpendicular stripe domains, namely with giant A, there is no phase transition at finite T: the stripe domains are progressively disordered with increasing T. Finite-size effects are shown and discussed.
Quantum correlations of an entangled state propagating through a phase-sensitive amplifier
NASA Astrophysics Data System (ADS)
Li, Tian; Anderson, Brian; Horrom, Travis; Glasser, Ryan; Jones, Kevin; Lett, Paul
2015-05-01
We investigate the advance and delay of information transmitted through an optical phase-sensitive amplifier (PSA). We start with a two-mode entangled state created by four-wave mixing in hot 85Rb vapor and measure the mutual information shared by the two modes. We then pass one of these two modes through a PSA and investigate the shift of the mutual information as a function of the PSA phase. The cross-correlation between the two modes of a bipartite EPR state can be advanced by propagation through a fast-light medium and, the extra noise added by a phase-insensitive amplifier has been shown to limit the advance of entanglement, preventing the mutual information from traveling superluminally. In the case of a PSA, however, it is well known that no extra noise will be added for the correct PSA phase (e.g. at the maximal amplification and the maximal deamplification). It is therefore of interest to examine the behavior of the dispersion and the mutual information when passing a signal through a PSA operated at different phases. The behavior of other correlation measures like the quantum discord will be presented as well. Based upon work supported by AFOSR and NSF (PFC at JQI).
TRANSITION STATE FOR THE GAS-PHASE REACTION OF URANIUM HEXAFLUORIDE WITH WATER
Garrison, S; James Becnel, J
2008-03-18
Density Functional Theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transitions states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF{sub 6}, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F{sub 5}, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structure and relative energies of the reacting complex and transition state. However, a significant change in the product complex structure was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF{sub 4}, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF{sub 6} with water.
Transition state for the gas-phase reaction of uranium hexafluoride with water.
Garrison, Stephen L; Becnel, James M
2008-06-19
Density functional theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transition states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF 6, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F 5, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structures and relative energies of the reacting complex and transition state. However, a significant change in the structure of the product complex was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF 4, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF 6 with water. PMID:18500792
Geometric quantum gates in liquid-state NMR based on a cancellation of dynamical phases
NASA Astrophysics Data System (ADS)
Ota, Yukihiro; Goto, Yoshito; Kondo, Yasushi; Nakahara, Mikio
2009-11-01
A proposal for applying nonadiabatic geometric phases to quantum computing, called double-loop method [S.-L. Zhu and Z. D. Wang, Phys. Rev. A 67, 022319 (2003)], is demonstrated in a liquid-state nuclear magnetic-resonance quantum computer. Using a spin-echo technique, the original method is modified so that quantum gates are implemented in a standard high-precision nuclear magnetic-resonance system for chemical analysis. We show that a dynamical phase is successfully eliminated and a one-qubit quantum gate is realized although the gate fidelity is not high.
Prediction of a metastable cubic phase for the transition metals with hcp ground state.
NASA Astrophysics Data System (ADS)
de Coss, Romeo; Aguayo, Aaron; Murrieta, Gabriel
2007-03-01
The discovery of a metastable phase for a given material is interesting because corresponds to a new bonding and new properties are expected. The calculation of the total-energy along the Bain path is frequently used as a method to find tetragonal metastable states. However, a local minimum in the tetragonal distortion is not a definitive proof of a metastable state, and the elastic stability needs to be evaluated. In a previous work, using the elastic stability criteria for a cubic structure, we have shown that the transition metals with hcp ground state; Ti, Zr, and Hf have a fcc metastable phase [Aguayo, G. Murrieta, and R. de Coss, Phys. Rev. B 65, 092106 (2002)]. That result is interesting since the fcc crystal structure does not appear in the current pressure-temperature phase diagram of these metals, and support the experimental observations of fcc Ti and Zr in thin films. In the present work, we extend the elastic stability study of the fcc structure to the non-magnetic transition metals with hcp ground state; Sc, Ti, Y, Zr, Tc, Ru, Hf, Re, and Os. We find that all the metals involved in this study have a metastable fcc structure. From these results, substrates on which the fcc structure of these metals could be growth epitaxially are predicted.
Meeker, Rick; Steurer, Mischa; Li, Hui; Edrington, Chris; Dale, Steinar; Faruque, MD Omar; Schoder, Karl; McLaren, Peter G.; Liu, Liming; Ravindra, Harsha; Henry, Shawn; Zhou, Yan; Liu, Xiaohu; Springstroh, Aaron; Click, David; Reedy, Robert; Moaveni, Houtan; Davis, Kristopher; Cromer, Charlie; Pappalardo, Anthoney; Krueger, Rodica; Domijan, Alexander; Islam, Arif; Islam, Mujahidil; Damole, Ademole
2012-03-30
This report provides details on the activities and accomplishments of Phase 1 of the Sunshine State Solar Grid Initiative (SUNGRIN) Project for the period beginning 4/28/2010 and ending 12/31/2011. SUNGRIN is a five-phase high-penetration solar PV project within the Systems Integration (SI) area of the Solar Energy Technologies (SETP) Program, under the SunShot Initiative. SUNGRIN is focused on understanding and enabling high-penetration grid-connected solar PV through simulation assisted studies of actual Florida utility high-penetration distribution circuits as well as substations and, to a limited extent, the bulk power system. Each phase builds and expands upon the efforts of the previous phase, leading to a comprehensive examination and understanding of high-penetration solar PV issues, from the solar resource to the conversion and integration technologies to the electric power system, with Florida and it’s utility partners providing the broad range of conditions and system integration scenarios necessary to develop useful insight and solutions. This phase, Phase 1, was funded with American Recovery and Reinvestment Act (ARRA) funds. This version of the final report is organized to align with statement of project objectives (SOPO) critical milestones.
NASA Astrophysics Data System (ADS)
Eason, R. P.; Sun, C.; Dick, A. J.; Nagarajaiah, S.
2015-05-01
Response attenuation of a linear primary structure (PS)-nonlinear tuned mass damper (NTMD) dynamic system with and without an adaptive-length pendulum tuned mass damper (ALPTMD) in a series configuration is studied by using numerical and experimental methods. In the PS-NTMD system, coexisting high and low amplitude solutions are observed in the experiment, validating previous numerical efforts. In order to eliminate the potentially dangerous high amplitude solutions, a series ALPTMD with a mass multiple orders of magnitude smaller than the PS is added to the NTMD. The ALPTMD is used in order to represent the steady-state behavior of a smart tuned mass damper (STMD). In the experiment, the length of the pendulum is adjusted such that its natural frequency matches the dominant frequency of the harmonic ground motions. In the present study, the proposed ALPTMD can be locked so that it is unable to oscillate and influence the dynamics of the system in order to obtain the benefits provided by the NTMD. The experimental data show good qualitative agreement with numerical predictions computed with parameter continuation and time integration methods. Activation of the ALPTMD can successfully prevent the transition of the response from the low amplitude solution to the high amplitude solution or return the response from the high amplitude solution to the low amplitude solution, thereby protecting the PS.
Metamaterial electromagnetic wave absorbers.
Watts, Claire M; Liu, Xianliang; Padilla, Willie J
2012-06-19
The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch-the metamaterial perfect absorber (MPA)-has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed. PMID:22627995
Absorber coatings' degradation
Moore, S.W.
1984-01-01
This report is intended to document some of the Los Alamos efforts that have been carried out under the Department of Energy (DOE) Active Heating and Cooling Materials Reliability, Maintainability, and Exposure Testing program. Funding for these activities is obtained directly from DOE although they represent a variety of projects and coordination with other agencies. Major limitations to the use of solar energy are the uncertain reliability and lifetimes of solar systems. This program is aimed at determining material operating limitations, durabilities, and failure modes such that materials improvements can be made and lifetimes can be extended. Although many active and passive materials and systems are being studied at Los Alamos, this paper will concentrate on absorber coatings and degradation of these coatings.
Epifanovsky, Evgeny; Polyakov, Igor; Grigorenko, Bella; Nemukhin, Alexander; Krylov, Anna I
2009-07-14
We present the results of quantum chemical calculations of the electronic properties of the anionic form of the green fluorescent protein chromophore in the gas phase. The vertical detachment energy of the chromophore is found to be 2.4-2.5 eV, which is below the strongly absorbing ππ* state at 2.6 eV. The vertical excitation of the lowest triplet state is around 1.9 eV, which is below the photodetachment continuum. Thus, the lowest bright singlet state is a resonance state embedded in the photodetachment continuum, whereas the lowest triplet state is a regular bound state. Based on our estimation of the vertical detachment energy, we attribute a minor feature in the action spectrum as due to the photodetachment transition. The benchmark results for the bright ππ* state demonstrated that the scaled opposite-spin method yields vertical excitation within 0.1 eV (20 nm) from the experimental maximum at 2.59 eV (479 nm). We also report estimations of the vertical excitation energy obtained with the equation-of-motion coupled cluster with the singles and doubles method, a multireference perturbation theory corrected approach MRMP2 as well as the time-dependent density functional theory with range-separated functionals. Expanding the basis set with diffuse functions lowers the ππ* vertical excitation energy by 0.1 eV at the same time revealing a continuum of "ionized" states, which embeds the bright ππ* transition. PMID:26610014
Exploring the phase space of multiple states in highly turbulent Taylor-Couette flow
NASA Astrophysics Data System (ADS)
van der Veen, Roeland; Huisman, Sander; Dung, On Yu; Tang, Ho Lun; Sun, Chao; Lohse, Detlef
2015-11-01
It was recently found that multiple turbulent states exist for large Reynolds number (Re =106) Taylor-Couette flow in the regime of ultimate turbulence. Here we investigate how the transitions between the multiple states depend on the Reynolds number in the range of Re =105 to 2 .106 , by measuring global torque and local velocity while probing the phase space spanned by the rotation rates of the inner and outer cylinder. This sheds light on the question whether multiple states persist for Reynolds numbers beyond those currently reached. By mapping the flow structures for various rotation ratios in two Taylor-Couette setups with equal radius ratio but different aspect ratio, we furthermore investigate the influence of aspect ratio on the characteristics of the multiple states.
Wei, T.-C.
2010-06-15
We consider quantum states under the renormalization-group (RG) transformations introduced by Verstraete et al. [Phys. Rev. Lett. 94, 140601 (2005)] and propose a quantification of entanglement under such RGs (via the geometric measure of entanglement). We examine the resulting entanglement under RG transformations for the ground states of ''matrix-product-state'' Hamiltonians constructed by Wolf et al. [Phys. Rev. Lett. 97, 110403 (2006)] that possess quantum phase transitions. We find that near critical points, the ground-state entanglement exhibits singular behavior. The singular behavior within finite steps of the RG obeys a scaling hypothesis and reveals the correlation length exponent. However, under the infinite steps of RG transformation, the singular behavior is rendered different and is universal only when there is an underlying conformal-field-theory description of the critical point.
Phase diagram of the Kohn-Luttinger superconducting state for bilayer graphene
NASA Astrophysics Data System (ADS)
Kagan, Maxim Yu.; Mitskan, Vitaly A.; Korovushkin, Maxim M.
2015-06-01
The effect of Coulomb interaction between Dirac fermions on the formation of the Kohn-Luttinger superconducting state in bilayer doped graphene is studied disregarding of the effect of the van der Waals potential of the substrate and impurities. The phase diagram determining the boundaries of superconductive domains with different types of symmetry of the order parameter is built using the extended Hubbard model in the Born weak-coupling approximation with allowance for the intratomic, interatomic, and interlayer Coulomb interactions between electrons. It is shown that the Kohn-Luttinger polarization contributions up to the second order of perturbation theory in the Coulomb interaction inclusively and an account for the long-range intraplane Coulomb interactions significantly affect the competition between the superconducting phases with the f-, p + ip-, and d + id-wave symmetries of the order parameter. It is demonstrated that the account for the interlayer Coulomb interaction enhances the critical temperature of the transition to the superconducting phase.
Ground state and zero temperature phase diagrams of the XXZ antiferromagnetic spin- {1}/{2} chain
NASA Astrophysics Data System (ADS)
Zhou, P.
1990-05-01
An expression of the XXZ model is given from which the Ising, isotropic XY and Heisenberg models may be more properly obtained by varying only one anisotropy parameter. The ground state and spin configuration of the antiferromagnetic quasi-classical s = {1}/{2}XXZ chain in a magnetic field of arbitrary direction are studied. The phase diagrams with a longitudinal ( h⊥ = 0) and a transverse field ( h‖ = 0) are presented. Because we take into account an effect of anisotropy in the Zeeman interaction, the phase diagrams are quite different from those given by Kurmann, et al. [Physica A 112 (1982) 235]. A ferromagnetic-antiferromagnetic first order phase transition is indicated for the Ising case with h⊥=0.
Park, Sunghun; Recher, Patrik
2015-12-11
A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages eV=±(α-2πl)ℏ/T_{J}, where α=π/2 is the exchange phase of the two circulating MBS, T_{J} is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange. PMID:26705644
Dipolar recoupling in solid state NMR by phase alternating pulse sequences
Lin, J.; Bayro, M.; Griffin, R. G.; Khaneja, N.
2009-01-01
We describe some new developments in the methodology of making heteronuclear and homonuclear recoupling experiments in solid state NMR insensitive to rf-inhomogeneity by phase alternating the irradiation on the spin system every rotor period. By incorporating delays of half rotor periods in the pulse sequences, these phase alternating experiments can be made γ encoded. The proposed methodology is conceptually different from the standard methods of making recoupling experiments robust by the use of ramps and adiabatic pulses in the recoupling periods. We show how the concept of phase alternation can be incorporated in the design of homonuclear recoupling experiments that are both insensitive to chemical-shift dispersion and rf-inhomogeneity. PMID:19157931
NASA Astrophysics Data System (ADS)
Park, Sunghun; Recher, Patrik
2015-12-01
A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages e V =±(α -2 π l )ℏ/TJ, where α =π /2 is the exchange phase of the two circulating MBS, TJ is the half rotation time of MBS, and l an integer. This result constitutes a clear experimental signature of Majorana fermion exchange.
Equation of state and phase diagram of ammonia at high pressures from ab initio simulations.
Bethkenhagen, Mandy; French, Martin; Redmer, Ronald
2013-06-21
We present an equation of state as well as a phase diagram of ammonia at high pressures and high temperatures derived from ab initio molecular dynamics simulations. The predicted phases of ammonia are characterized by analyzing diffusion coefficients and structural properties. Both the phase diagram and the subsequently computed Hugoniot curves are compared to experimental results. Furthermore, we discuss two methods that allow us to take into account nuclear quantum effects, which are of considerable importance in molecular fluids. Our data cover pressures up to 330 GPa and a temperature range from 500 K to 10,000 K. This regime is of great interest for interior models of the giant planets Uranus and Neptune, which contain, besides water and methane, significant amounts of ammonia. PMID:23802968
NASA Astrophysics Data System (ADS)
Buehler, Janine Sylvia
The aim of this dissertation is to improve our understanding of the crust and uppermost mantle structure in the western United States, profiting from the wealth of regional phase data recorded at USArray stations. USArray, a transportable seismic array of ˜400 seismometers, has greatly increased seismic data coverage across the United States in the past few years, and allows imaging of the lithosphere of the North American continent with better resolution and new methods. The regional phases are often challenging to analyze, especially in a tectonically-active region like the western United States, because of their sensitivities to the heterogeneities of the crust and uppermost mantle. However, knowledge of the seismic structure of the lithosphere is not only essential in order to accurately image the velocity structure at greater depths, but also for constraining geodynamic models that reconstruct the tectonic evolution of the continent, and hence the information that is carried by the regional phases is very valuable. The data set used in this study consists mostly of the regional seismic phases Pn and Sn, which propagate horizontally along the Moho in the mantle lid and constrain the seismic velocity structure at a confined depth. We applied traditional tomographic methods that profit from the improved ray coverage through USArray, but also employed array-based techniques that take advantage of the regular station spacing of the transportable array and don't depend on regularization. In addition, we used stacking methods to image the propagation efficiency of the Sn phase, which is often highly attenuated in tectonically active regions, on a regional scale. The results complement other seismic studies that average over greater depth intervals, such as surface- and body-wave tomographies and anisotropy analysis from shear-wave splitting, to provide information on temperature, composition, and tectonic processes at depth. Comparisons between Pn azimuthal
Ground state phase transition in the Nilsson mean-field plus standard pairing model
NASA Astrophysics Data System (ADS)
Guan, Xin; Xu, Haocheng; Zhang, Yu; Pan, Feng; Draayer, Jerry P.
2016-08-01
The ground state phase transition in Nd, Sm, and Gd isotopes is investigated by using the Nilsson mean-field plus standard pairing model based on the exact solutions obtained from the extended Heine-Stieltjes correspondence. The results of the model calculations successfully reproduce the critical phenomena observed experimentally in the odd-even mass differences, odd-even differences of two-neutron separation energy, and the α -decay and double β--decay energies of these isotopes. Since the odd-even effects are the most important signatures of pairing interactions in nuclei, the model calculations yield microscopic insight into the nature of the ground state phase transition manifested by the standard pairing interaction.
Cooperative Lamb shift and the cooperative decay rate for an initially detuned phased state
Friedberg, Richard; Manassah, Jamal T.
2010-04-15
The cooperative Lamb shift (CLS) is hard to measure because in samples much larger than a resonant wavelength it is much smaller, for an initially prepared resonantly phased state, than the cooperative decay rate (CDR). We show, however, that if the phasing of the initial state is detuned so that the spatial wave vector is k{sub 1} congruent with k{sub 0{+-}}O((1/R)) (where k{sub 0}={omega}{sub 0}/c is the resonant frequency), the CLS grows to 'giant' magnitudes making it comparable to the CDR. Moreover, for certain controlled values of detuning, the initial CDR becomes small so that the dynamical Lamb shift (DLS) can be measured over a considerable period of time.
Electronic Transport properties of SET and REST states of interfacial phase-change memory
NASA Astrophysics Data System (ADS)
Nakamura, Hisao; Tominaga, Junji; Asai, Yoshihiro; Rungger, Ivan; Narayan, Awadhesh; Sanvito, Stefano
2015-03-01
The phase change memory (PCM) is one of most promising nonvolatile information storage technologies. Recently, the superlattice structure of GeTe/Sb2Te3 is proposed as PCM to reduce the restive switching energy. This PCM is called interfacial PCM (iPCM) and it is considered that SET and RESET states are realized only by the flip-flop transition of Ge atoms in crystal phase because of small loss of entropy. Furthermore, the GeTe is sandwiched by Sb2Te3 topological insulator. In this study, we performed the first principles electric transport calculations including spin-orbit interactions. We presents the mechanism of resistive switch by the transition of Ge atoms as well as the volume change effect and the role of spin-orbit interaction to resistance ration of SET and RESE states.
Phase transition kinetics and surface binding states of methylammonium lead iodide perovskite.
Rajendra Kumar, G; Dennyson Savariraj, A; Karthick, S N; Selvam, S; Balamuralitharan, B; Kim, Hee-Je; Viswanathan, K K; Vijaykumar, M; Prabakar, Kandasamy
2016-03-01
We have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS. PMID:26894928
A quantum phase switch between a solid state spin and a photon
NASA Astrophysics Data System (ADS)
Sun, Shuo; Kim, Hyochul; Solomon, Glenn; Waks, Edo
The implementation of quantum network and distributive quantum computation replies on strong interactions between stationary matter qubits and flying photons. The spin of a single electron confined in a quantum dot is considered as a promising matter qubit as it possesses microsecond coherence time and allows picosecond timescale control using optical pulses. The quantum dot spin can also interact with a photon by controlling the optical response of a strongly coupled cavity. In this talk I will discuss our recent work on an experimental realization of a spin-photon quantum phase switch using a single spin in a quantum dot strongly coupled to a photonic crystal cavity. We show large modulation of the cavity reflection spectrum by manipulating the spin states of the quantum dot, which enables us to control the quantum state of a reflected photon. We also show the complementary effect where the presence of a single photon switches the quantum state of the spin. The reported spin-photon quantum phase operation can switch spin or photon states in picoseconds timescale, representing an important step towards GHz semiconductor based quantum logic devices on-a-chip and solid-state implementations of quantum networks.
Quantum phase transition triggering magnetic bound states in the continuum in graphene
NASA Astrophysics Data System (ADS)
Guessi, L. H.; Marques, Y.; Machado, R. S.; Kristinsson, K.; Ricco, L. S.; Shelykh, I. A.; Figueira, M. S.; de Souza, M.; Seridonio, A. C.
2015-12-01
Graphene hosting a pair of collinear adatoms in the phantom atom configuration has density of states vanishing in the vicinity of the Dirac point which can be described in terms of the pseudogap scaling as cube of the energy, Δ ∝|ɛ| 3 , which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015), 10.1103/PhysRevB.92.045409]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. Here, we explore the effects of nonlocal coupling characterized by the Fano factor of interference q0, tunable by changing the slope of the Dirac cones in the graphene band structure. We demonstrate that three distinct regimes can be identified: (i) for q0
Optical phase information writing and storage in populations of metastable quantum states
Djotyan, G. P.; Sandor, N.; Bakos, J. S.; Soerlei, Zs.
2009-10-15
We propose a scheme for robust writing and storage of optical phase information in populations of metastable states of the atoms with a tripod structure of levels by using frequency-chirped laser pulses. The method provides much longer storage times compared with the schemes based on the collective atomic spin coherences. A negligible excitation of the atom provides immunity to decoherence induced by decay of the excited states. The method is robust against small-to-medium variations in the laser pulse intensity and speed of the chirp and, being insensitive to resonance conditions, it is effective both in homogeneously and inhomogeneously broadened media.
Experimental investigation of a steady-state dynamical phase transition in a Jaynes-Cummings dimer
NASA Astrophysics Data System (ADS)
Raftery, James; Sadri, Darius; Mandt, Stephan; Tureci, Hakan; Houck, Andrew
Experimental progress in circuit-QED has made it possible to study non-equilibrium many-body physics using strongly correlated photons. Such open and driven systems can display new types of dynamical phase transitions. A steady state transition has also been predicted for a Jaynes-Cummings dimer where the photon current between the two cavities acts as an order parameter. Here, we discuss the theory and report measurements of the steady-state behavior of a circuit-QED dimer with in situ tunable inter-cavity coupling and on-site photon-photon interaction. Recently deceased.
Ground State of Magnetic Dipoles on a Two-Dimensional Lattice: Structural Phases in Complex Plasmas
Feldmann, J. D.; Kalman, G. J.; Hartmann, P.; Rosenberg, M.
2008-02-29
We study analytically and by molecular dynamics simulations the ground state configuration of a system of magnetic dipoles fixed on a two-dimensional lattice. We find different phases, in close agreement with previous results. Building on this result and on the minimum energy requirement we determine the equilibrium lattice configuration, the magnetic order (ferromagnetic versus antiferromagnetic), and the magnetic polarization direction of a system of charged mesoscopic particles with magnetic dipole moments, in the domain where the strong electrostatic coupling leads to a crystalline ground state. Orders of magnitudes of the parameters of the system relevant to possible future dusty plasma experiments are discussed.
Feddema, J.T.; Robinett, R.D.; Driessen, B.J.
1998-03-10
This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that one can begin to design provably asymptotically stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove asymptotically stable group behavior is especially important for applications such as locating military targets or land mines.
Application of the principle of corresponding states to two phase choked flow
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Simoneau, R. J.
1973-01-01
It is pointed out that several fluids including methane, oxygen, and nitrogen appear to form an average parametric plot which indicates that the isenthalpic Joule-Thomson coefficient must nearly obey the principle of corresponding states. With this as a basis, it was assumed that there could be several thermodynamic flow processes which nearly obey the principle. An examination was made to determine whether two-phase choked flow could be one of them. The analysis is described and the results are given.
Invariant criteria for bound states, degree of ionization, and plasma phase transition
NASA Technical Reports Server (NTRS)
Girardeau, M. D.
1990-01-01
Basis invariant characterizations of bound states and bound fraction of a partially ionized hydrogen plasma are given in terms of properties of the spectrum of eigenvalues and eigenfunctions of the equilibrium quantum statistical one-proton-one-electron reduced density matrix. It is suggested that these can be used to place theories of a proposed plasma-ionization phase transition on a firm foundation. This general approach may be relevant to cosmological questions such as the quark deconfinement-confinement transition.
Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system
Pang, Mingjun; Zhan, Yongzhong; Du, Yong
2013-02-15
The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.
ERIC Educational Resources Information Center
Northern Montana Coll., Havre.
The dissemination phase (Phase II) of the Rural Shared Services Project is reported in this document. Efforts of the dissemination phase were concentrated in 5 target states: Vermont, Georgia, Wyoming, Montana, and New Mexico; national dissemination was limited to attendance at national conferences, the U. S. Office of Education PREP materials for…
Classification of ground states and normal modes for phase-frustrated multicomponent superconductors
NASA Astrophysics Data System (ADS)
Weston, Daniel; Babaev, Egor
2013-12-01
We classify ground states and normal modes for n-component superconductors with frustrated intercomponent Josephson couplings, focusing on n=4. The results should be relevant not only to multiband superconductors, but also to Josephson-coupled multilayers and Josephson-junction arrays. It was recently discussed that three-component superconductors can break time-reversal symmetry as a consequence of phase frustration. We discuss how to classify frustrated superconductors with an arbitrary number of components. Although already for the four-component case there are a large number of different combinations of phase-locking and phase-antilocking Josephson couplings, we establish that there are a much smaller number of equivalence classes where properties of frustrated multicomponent superconductors can be mapped to each other. This classification is related to the graph-theoretical concept of Seidel switching. Numerically, we calculate ground states, normal modes, and characteristic length scales for the four-component case. We report conditions of appearance of new accidental continuous ground-state degeneracies.
Computer simulations of liquid silica: Equation of state and liquid-liquid phase transition
NASA Astrophysics Data System (ADS)
Saika-Voivod, Ivan; Sciortino, Francesco; Poole, Peter H.
2001-01-01
We conduct extensive molecular dynamics computer simulations of two models for liquid silica [the model of Woodcock, Angell and Cheeseman, J. Phys. Chem. 65, 1565 (1976); and that of van Beest, Kramer, and van Santen, Phys. Rev. Lett. 64, 1955 (1990)] to determine their thermodynamic properties at low temperature T across a wide density range. We find for both models a wide range of states in which isochores of the potential energy U are a linear function of T3/5, as recently proposed for simple liquids [Rosenfeld and P. Tarazona, Mol. Phys. 95, 141 (1998)]. We exploit this behavior to fit an accurate equation of state to our thermodynamic data. Extrapolation of this equation of state to low T predicts the occurrence of a liquid-liquid phase transition for both models. We conduct simulations in the region of the predicted phase transition, and confirm its existence by direct observation of phase separating droplets of atoms with distinct local density and coordination environments.
Electrochemically regenerable carbon dioxide absorber
NASA Technical Reports Server (NTRS)
Woods, R. R.; Marshall, R. D.; Schubert, F. H.; Heppner, D. B.
1979-01-01
Preliminary designs were generated for two electrochemically regenerable carbon dioxide absorber concepts. Initially, an electrochemically regenerable absorption bed concept was designed. This concept incorporated the required electrochemical regeneration components in the absorber design, permitting the absorbent to be regenerated within the absorption bed. This hardware was identified as the electrochemical absorber hardware. The second hardware concept separated the functional components of the regeneration and absorption process. This design approach minimized the extravehicular activity component volume by eliminating regeneration hardware components within the absorber. The electrochemical absorber hardware was extensively characterized for major operating parameters such as inlet carbon dioxide partial pressure, process air flow rate, operational pressure, inlet relative humidity, regeneration current density and absorption/regeneration cycle endurance testing.
Liquid Hydrogen Absorber for MICE
Ishimoto, S.; Suzuki, S.; Yoshida, M.; Green, Michael A.; Kuno, Y.; Lau, Wing
2010-05-30
Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with {approx}2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.
Broadband patterned magnetic microwave absorber
Li, Wei; Wu, Tianlong; Wang, Wei; Guan, Jianguo; Zhai, Pengcheng
2014-07-28
It is a tough task to greatly improve the working bandwidth for the traditional flat microwave absorbers because of the restriction of available material parameters. In this work, a simple patterning method is proposed to drastically broaden the absorption bandwidth of a conventional magnetic absorber. As a demonstration, an ultra-broadband microwave absorber with more than 90% absorption in the frequency range of 4–40 GHz is designed and experimentally realized, which has a thin thickness of 3.7 mm and a light weight equivalent to a 2-mm-thick flat absorber. In such a patterned absorber, the broadband strong absorption is mainly originated from the simultaneous incorporation of multiple λ/4 resonances and edge diffraction effects. This work provides a facile route to greatly extend the microwave absorption bandwidth for the currently available absorbing materials.
Warm Absorber Diagnostics of AGN Dynamics
NASA Astrophysics Data System (ADS)
Kallman, Timothy
Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are
NASA Technical Reports Server (NTRS)
Pogorzelski, Ronald J.
2004-01-01
When electronic oscillators are coupled to nearest neighbors to form an array on a hexagonal lattice, the planar phase distributions desired for excitation of a phased array antenna are not steady state solutions of the governing non-linear equations describing the system. Thus the steady state phase distribution deviates from planar. It is shown to be possible to obtain an exact solution for the steady state phase distribution and thus determine the deviation from the desired planar distribution as a function of beam steering angle.
NASA Astrophysics Data System (ADS)
Okamoto, Kiyomi; Tonegawa, Takashi; Sakai, Tôru
2016-06-01
We investigate the ground-state phase diagram of the bond-alternating S = 2 quantum spin chain with the XXZ and on-site anisotropies. For the on-site anisotropies, in addition to the popular D2sumnolimitsj (Sjz)2 term, we consider the D4sumnolimitsj (Sjz)4 term. Mainly we use the exact diagonalization and the level spectroscopy analysis. We show that the Haldane state, large-D state and the Dimer2 state belong to the same trivial phase, by finding the existence of adiabatic paths directly connecting these states without the quantum phase transition. Similarly, we show that the intermediate-D state and the Dimer1 state belong to the same symmetry protected topological phase.
Equation of state and reaction rate for condensed-phase explosives
NASA Astrophysics Data System (ADS)
Wescott, B. L.; Stewart, D. Scott; Davis, W. C.
2005-09-01
The wide-ranging equation of state is a nonideal equation of state based on empirical fitting forms argued from thermodynamic considerations that yield the proper physical features of detonation. The complete equation of state forms are presented and the equation of state and a reaction rate are calibrated for the condensed-phase explosive PBX-9502. Experimental overdriven Hugoniot data are used to calibrate the products equation of state off the principal isentrope passing through the Chapman-Jouguet state. Shock Hugoniot data are used to calibrate the reactants equation of state. The normal detonation shock speed-shock curvature data (Dn-κ) from rate-stick measurements and shock initiation data from wedge tests are used to calibrate the reaction rate. Simulations are carried out that predict detailed particle velocity transients that are measured experimentally with embedded electromagnetic gauge measurements from gas-gun experiments. Multidimensional simulations of steady detonation in a right circular cylinder rate stick are carried out and compared with experiment.
Topological phase and edge states dependence of the RKKY interaction in zigzag silicene nanoribbon
NASA Astrophysics Data System (ADS)
Zare, Moslem; Parhizgar, Fariborz; Asgari, Reza
2016-07-01
We propose versatile materials based on the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in a zigzag silicene nanoribbon (ZSNR) on half filling in the presence of an out-of-plane electric field. We show that the topological phase transition in the band dispersion of ZSNR can be probed by using the RKKY interaction. We find that, due to the zero-energy edge states of the ZSNR, the exchange coupling is significantly enhanced when the impurities are located on the zigzag edges, and also explore that the strength of the interaction in the topological insulator phase is much greater than that when the system is in the band insulator region. We present a model to investigate the phase of a system of two magnetic impurities located on the edge of the ZSNR and find that three different magnetic phases, spiral, ferromagnetic, and antiferromagnetic, are possible for different values of the electric field. This electrical tunability of the magnetic phases in silicene can be explored by using current experimental techniques and can be of interest in the field of spintronics.
Geometry-dependent phase, stress state and electrical properties in nickel-silicide nanowires
NASA Astrophysics Data System (ADS)
Wang, C. C.; Lai, W. T.; Hsiao, Y. Y.; Chen, I. H.; George, T.; Li, P. W.
2016-05-01
We report that the geometry of single-crystalline Si nanowires (NWs) prior to salicidation at 500 °C is the key factor controlling the phase, stress state, and electrical resistivity of the resulting Ni x Si y NWs of width less than 100 nm. This is a radical departure from previous observations of a single phase formation for nickel silicides generated from the silicidation of bulk Si substrates. The phase transition from NiSi for large NWs ( W Si NW = 250–450 nm) to Ni2Si for small NWs ( W Si NW = 70–100 nm) is well correlated with the observed volumetric expansion and electrical resistivity variation with the NW width. For the extremely small dimensions of Ni x Si y NWs, we propose that the preeminent, kinetics-based Zhang and d’Heurle model for salicidation be modified to a more thermodynamically-governed, volume-expansion dependent Ni x Si y phase formation. A novel, plastic deformation mechanism is proposed to explain the observed, geometry-dependent Ni x Si y NW phase formation that also strongly influences the electrical performance of the NWs.
NASA Astrophysics Data System (ADS)
Delagrange, Raphaelle; Weil, R.; Kasumov, A.; Bouchiat, H.; Deblock, R.; Luitz, D. J.; Meden, V.
The Kondo effect is a many-body phenomenon that screens the magnetic moment of an impurity in a metal. The associated singlet state can be probed in a single impurity by electronic transport in a quantum dot (QD), here made of a carbon nanotube (CNT), which provides a localized electron between the two contacts. Using superconducting leads, one can investigate the competition between the Kondo effect and the superconductivity induced in the CNT. The superconductivity can destroy the Kondo singlet in favor of a magnetic doublet, leading to a sign reversal of the supercurrent in the S-CNT-S junction. This singlet-doublet transition depends on the Kondo temperature and the superconducting gap, as well as the position of the impurity level. We demonstrate experimentally that the superconducting phase difference across the QD can also control this magnetic transition. We use the measurement of the relation between the supercurrent and this superconducting phase as a tool to probe the transition. We show that it has a distinctly anharmonic behavior, that reveals the phase-mediated singlet to doublet transition, in good agreement with finite temperature quantum Monte Carlo calculations. We extract as well a phase diagram of the phase-controlled quantum transition at zero temperature.
Imaging Rayleigh wave attenuation and phase velocity in the western and central United States
NASA Astrophysics Data System (ADS)
Bao, X.; Dalton, C. A.; Jin, G.; Gaherty, J. B.
2013-12-01
The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, little is known about the attenuation structure of the North American upper mantle. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity, and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. We jointly invert Rayleigh wave phase and amplitude observations for phase velocity and attenuation maps for the western and central United States using USArray data. This approach exploits the amplitudes' sensitivity to velocity and the phase delays' sensitivity to attenuation. The phase and amplitude data are measured in the period range 20--100 s using a new interstation cross-correlation approach, based on the Generalized Seismological Data Functional algorithm, that takes advantage of waveform similarity at nearby stations. The Rayleigh waves are generated from 670 large teleseismic earthquakes that occurred between 2006 and 2012, and measured from all available Transportable Array stations. We consider two separate and complementary approaches for imaging attenuation variations: (1) the Helmholtz tomography (Lin et al., 2012) and (2) two-station path tomography. Results obtained from the two methods are contrasted. We provide a preliminary interpretation based on the observed relationship between Rayleigh wave attenuation and phase velocity.
Phase-slip states in the normal-superconducting relaxation of current-biased microstrips
Butler, D.P.; Hsiang, T.Y.
1987-03-01
The authors have solved the generalized time-dependent Ginzburg-Landau (TDGL) equations of Kramer and Watts-Tobin numerically. The solutions are used to predict the relaxation behavior of a microstrip biased below its dc critical current and excited into the resistive state by the application of a supercritical current pulse of a fixed duration. They have studied the relaxation behavior of the gap parameter and voltage along the microstrip as a function of the current pulse amplitude and bias magnitude. The relaxation is found to occur through a succession of phase-slip oscillations. The relaxation behavior is determined by the initial phase-slip state created by the current pulse. The maximum resistance attained increases rapidly, then saturates at a value less than the normal state resistance. The numerical solutions exhibit a region in which a relaxation time anomaly occurs with respect to the current pulse amplitude. In this region, the more highly excited states were found to relax faster. These features of the resistive relaxation behavior are found to be in qualitative agreement with their previous experimental measurements.
Hemispheric Specialization Varies with EEG Brain Resting States and Phase of Menstrual Cycle
Cacioppo, Stephanie; Bianchi-Demicheli, Francesco; Bischof, Paul; DeZiegler, Dominique; Michel, Christoph M.; Landis, Theodor
2013-01-01
A growing body of behavioral studies has demonstrated that women’s hemispheric specialization varies as a function of their menstrual cycle, with hemispheric specialization enhanced during their menstruation period. Our recent high-density electroencephalogram (EEG) study with lateralized emotional versus neutral words extended these behavioral results by showing that hemispheric specialization in men, but not in women under birth-control, depends upon specific EEG resting brain states at stimulus arrival, suggesting that hemispheric specialization may be pre-determined at the moment of the stimulus onset. To investigate whether EEG brain resting state for hemispheric specialization could vary as a function of the menstrual phase, we tested 12 right-handed healthy women over different phases of their menstrual cycle combining high-density EEG recordings and the same lateralized lexical decision paradigm with emotional versus neutral words. Results showed the presence of specific EEG resting brain states, associated with hemispheric specialization for emotional words, at the moment of the stimulus onset during the menstruation period only. These results suggest that the pre-stimulus EEG pattern influencing hemispheric specialization is modulated by the hormonal state. PMID:23638185
Source attack of decoy-state quantum key distribution using phase information
NASA Astrophysics Data System (ADS)
Tang, Yan-Lin; Yin, Hua-Lei; Ma, Xiongfeng; Fung, Chi-Hang Fred; Liu, Yang; Yong, Hai-Lin; Chen, Teng-Yun; Peng, Cheng-Zhi; Chen, Zeng-Bing; Pan, Jian-Wei
2013-08-01
Quantum key distribution (QKD) utilizes the laws of quantum mechanics to achieve information-theoretically secure key generation. This field is now approaching the stage of commercialization, but many practical QKD systems still suffer from security loopholes due to imperfect devices. In fact, practical attacks have successfully been demonstrated. Fortunately, most of them only exploit detection-side loopholes, which are now closed by the recent idea of measurement-device-independent QKD. On the other hand, little attention is paid to the source, which may still leave QKD systems insecure. In this work, we propose and demonstrate an attack that exploits a source-side loophole existing in qubit-based QKD systems using a weak coherent state source and decoy states. Specifically, by implementing a linear-optics unambiguous state discrimination measurement, we show that the security of a system without phase randomization—which is a step assumed in conventional security analyses but sometimes neglected in practice—can be compromised. We conclude that implementing phase randomization is essential to the security of decoy-state QKD systems under current security analyses.
Parry, J.
1995-02-01
Decontamination of heavy metals-polluted soils remains one of the most intractable problems of cleanup technology. Currently available techniques include extraction of the metals by physical and chemical means, such as acid leaching and electroosmosis, or immobilization by vitrification. There are presently no techniques for cleanup which are low cost and retain soil fertility after metals removal. But a solution to the problem could be on the horizon. A small but growing number of plants native to metalliferous soils are known to be capable of accumulating extremely high concentrations of metals in their aboveground portions. These hyperaccumulators, as they are called, contain up to 1,000 times larger metal concentrations in their aboveground parts than normal species. Their distribution is global, including many different families of flowering plants of varying growth forms, from herbaceous plants to trees. Hyperaccumulators absorb metals they do not need for their own nutrition. The metals are accumulated in the leaf and stem vacuoles, and to a lesser extent in the roots.
Chimera states in networks of phase oscillators: The case of two small populations
NASA Astrophysics Data System (ADS)
Panaggio, Mark J.; Abrams, Daniel M.; Ashwin, Peter; Laing, Carlo R.
2016-01-01
Chimera states are dynamical patterns in networks of coupled oscillators in which regions of synchronous and asynchronous oscillation coexist. Although these states are typically observed in large ensembles of oscillators and analyzed in the continuum limit, chimeras may also occur in systems with finite (and small) numbers of oscillators. Focusing on networks of 2 N phase oscillators that are organized in two groups, we find that chimera states, corresponding to attracting periodic orbits, appear with as few as two oscillators per group and demonstrate that for N >2 the bifurcations that create them are analogous to those observed in the continuum limit. These findings suggest that chimeras, which bear striking similarities to dynamical patterns in nature, are observable and robust in small networks that are relevant to a variety of real-world systems.
Quantum state engineering with flux-biased Josephson phase qubits by rapid adiabatic passages
Nie, W.; Huang, J. S.; Shi, X.; Wei, L. F.
2010-09-15
In this article, the scheme of quantum computing based on the Stark-chirped rapid adiabatic passage (SCRAP) technique [L. F. Wei, J. R. Johansson, L. X. Cen, S. Ashhab, and F. Nori, Phys. Rev. Lett. 100, 113601 (2008)] is extensively applied to implement quantum state manipulations in flux-biased Josephson phase qubits. The broken-parity symmetries of bound states in flux-biased Josephson junctions are utilized to conveniently generate the desirable Stark shifts. Then, assisted by various transition pulses, universal quantum logic gates as well as arbitrary quantum state preparations can be implemented. Compared with the usual {pi}-pulse operations widely used in experiments, the adiabatic population passages proposed here are insensitive to the details of the applied pulses and thus the desirable population transfers can be satisfyingly implemented. The experimental feasibility of the proposal is also discussed.
NASA Astrophysics Data System (ADS)
Wei, Tzu-Chieh
2010-06-01
We consider quantum states under the renormalization-group (RG) transformations introduced by Verstraete [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.94.140601 94, 140601 (2005)] and propose a quantification of entanglement under such RGs (via the geometric measure of entanglement). We examine the resulting entanglement under RG transformations for the ground states of “matrix-product-state” Hamiltonians constructed by Wolf [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.97.110403 97, 110403 (2006)] that possess quantum phase transitions. We find that near critical points, the ground-state entanglement exhibits singular behavior. The singular behavior within finite steps of the RG obeys a scaling hypothesis and reveals the correlation length exponent. However, under the infinite steps of RG transformation, the singular behavior is rendered different and is universal only when there is an underlying conformal-field-theory description of the critical point.
Chimera and phase-cluster states in populations of coupled chemical oscillators
NASA Astrophysics Data System (ADS)
Tinsley, Mark R.; Nkomo, Simbarashe; Showalter, Kenneth
2012-09-01
Populations of coupled oscillators may exhibit two coexisting subpopulations, one with synchronized oscillations and the other with unsynchronized oscillations, even though all of the oscillators are coupled to each other in an equivalent manner. This phenomenon, discovered about ten years ago in theoretical studies, was then further characterized and named the chimera state after the Greek mythological creature made up of different animals. The highly counterintuitive coexistence of coherent and incoherent oscillations in populations of identical oscillators, each with an equivalent coupling structure, inspired great interest and a flurry of theoretical activity. Here we report on experimental studies of chimera states and their relation to other synchronization states in populations of coupled chemical oscillators. Our experiments with coupled Belousov-Zhabotinsky oscillators and corresponding simulations reveal chimera behaviour that differs significantly from the behaviour found in theoretical studies of phase-oscillator models.
NASA Technical Reports Server (NTRS)
Fan, An-Fu; Sun, Nian-Chun; Zhou, Xin
1996-01-01
The Phase-dynamical properties of the squeezed vacuum state intensity-couple interacting with the two-level atom in an ideal cavity are studied using the Hermitian phase operator formalism. Exact general expressions for the phase distribution and the associated expectation value and variance of the phase operator have been derived. we have also obtained the analytic results of the phase variance for two special cases-weakly and strongly squeezed vacuum. The results calculated numerically show that squeezing has a significant effect on the phase properties of squeezed vacuum.
The use of lipids as phase change materials for thermal energy storage
Technology Transfer Automated Retrieval System (TEKTRAN)
Phase change materials (PCMs) are substances capable of absorbing and releasing large 2 amounts of thermal energy (heat or cold) as latent heat over constant temperature as they 3 undergo a change in state of matter (phase transition), commonly, between solid and 4 liquid phases. Since the late 194...
Hermitian-phase-operator treatment of the superfluid states in a quantum two-well problem
Kostrun, Marijan
2004-07-01
We apply the Hermitian phase operator method (HPOM), as discussed by Pegg and Barnett [D. T. Pegg and S. M. Barnett, Phys. Rev. A 39, 1665 (1989)] to a two-well Bose-Hubbard model. Application of the HPOM formalism yields an approximate quantum phase model, or a Schroedinger-like differential equation for the phase variable {theta}, which is a conjugate variable to the half of the number difference between the wells, m=(N{sub 1}-N{sub 2})/2. In the construction of the model we take care so that the Hermiticity of the original Bose-Hubbard model in number representation is inherited. We demonstrate that the quantum phase model supersedes two theoretical models suggested for the group of so-called 'normal' states, for which <{theta}>=
Mott insulating states and quantum phase transitions of correlated SU(2 N ) Dirac fermions
NASA Astrophysics Data System (ADS)
Zhou, Zhichao; Wang, Da; Meng, Zi Yang; Wang, Yu; Wu, Congjun
2016-06-01
The interplay between charge and spin degrees of freedom in strongly correlated fermionic systems, in particular of Dirac fermions, is a long-standing problem in condensed matter physics. We investigate the competing orders in the half-filled SU (2 N ) Hubbard model on a honeycomb lattice, which can be accurately realized in optical lattices with ultracold large-spin alkaline-earth fermions. Employing large-scale projector determinant quantum Monte Carlo simulations, we have explored quantum phase transitions from the gapless Dirac semimetals to the gapped Mott insulating phases in the SU(4) and SU(6) cases. Both of these Mott insulating states are found to be columnar valence bond solid (cVBS) and to be absent of the antiferromagnetic Néel ordering and the loop current ordering. Inside the cVBS phases, the dimer ordering is enhanced by increasing fermion components and behaves nonmonotonically as the interaction strength increases. Although the transitions generally should be of first order due to a cubic invariance possessed by the cVBS order, the coupling to gapless Dirac fermions can soften the transitions to second order through a nonanalytic term in the free energy. Our simulations provide important guidance for the experimental explorations of novel states of matter with ultracold alkaline-earth fermions.
Optimal Gaussian squeezed states for atom interferometry in the presence of phase diffusion
Tikhonenkov, Igor; Moore, Michael G.; Vardi, Amichay
2010-10-15
We optimize the signal-to-noise ratio of a Mach-Zehnder atom interferometer with Gaussian squeezed input states in the presence interactions. For weak interactions, our results coincide with those of Huang and Moore [Y. P. Huang and M. G. Moore, Phys. Rev. Lett. 100, 250406 (2008)], with an optimal initial number variance {sigma}{sub o{proportional_to}}N{sup 1/3} and an optimal signal-to-noise ratio s{sub o{proportional_to}}N{sup 2/3} for the total atom number N. As the interaction strength u increases past unity, phase diffusion becomes dominant, leading to a transition in the optimal squeezing from initial number squeezing to initial phase squeezing with {sigma}{sub o{proportional_to}{radical}}(uN) and s{sub o{proportional_to}{radical}}(N/u) shot-noise scaling. The initial phase squeezing translates into hold-time number squeezing, which is less sensitive to interactions than coherent states and improves s{sub o} by a factor of {radical}(u).
Crosson, Garry S; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary Kay; O'Day, Peggy A; Mueller, Karl T
2006-01-19
The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3-, 1 mol kg-1 of OH-, and pH approximately 13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10(-3), 10(-4), and 10(-5) molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10(-5) m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10(-3) m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and
Crosson, Garry S.; Choi, Sunkyung; Chorover, Jon; Amistadi, Mary K.; O'Day, Peggy A.; Mueller, Karl T.
2006-01-19
The weathering of a specimen kaolinite clay was studied over the course of 369 d via solid-state 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and high-field 27Al MAS NMR. The chosen baseline solution conditions (0.05 mol kg-1 of Al, 2 mol kg-1 of Na+, 1 mol kg-1 of NO3 -, 1 mol kg-1 of OH-, and pH ~13.8) approximate those of solutions leaking from waste tanks at the Hanford Site in Richland, WA. Nonradioactive Cs and Sr cations were added to this synthetic tank waste leachate (STWL) solution at concentrations of 10-3, 10-4, and 10-5 molal (m) to represent their radionuclide counterparts. The transformations of silicon- and aluminum-containing solid phase species were monitored quantitatively by using NMR spectroscopy, with the resulting spectra directly reporting the influence of the initial Cs and Sr on formation and transformation of the neo-formed solids. At the lowest concentration of Cs and Sr employed (10-5 m in each cation) peaks consistent with the formation of zeolite-like minerals were detected via 29Si and 27Al MAS NMR as early as 33 d. At concentrations of 10-3 m in each cation, new silicon species are not detected until 93 d, although neophases containing four-coordinate aluminum were detectable at earlier reaction times via 27Al MAS NMR. At the highest magnetic field strengths employed in this NMR study, deconvolutions of resonances detected in the tetrahedral region of the 27Al MAS spectra yielded multiple components, indicating the existence of at least four new aluminum-containing phases. Two of these phases are identified as sodalite and cancrinite through comparison with diffuse-reflectance infrared (DRIFT) spectra and powder X-ray diffraction (XRD) results, while a third phase may correlate with a previously detected aluminum-rich chabazite phase. All measurable solid reaction products have been quantified via their 27Al MAS resonances acquired at high magnetic field strengths (17.6 T), and the quantitative
NASA Astrophysics Data System (ADS)
Wesselski, Clarence J.
1994-05-01
The energy absorber that was developed for the CETA (Crew Equipment and Translation Aid) on Space Station Freedom is a metal on metal frictional type and has a load regulating feature that prevents excessive stroking loads from occurring while in operation. This paper highlights some of the design and operating aspects and the testing of this energy absorber.
NASA Technical Reports Server (NTRS)
Wesselski, Clarence J.
1994-01-01
The energy absorber that was developed for the CETA (Crew Equipment and Translation Aid) on Space Station Freedom is a metal on metal frictional type and has a load regulating feature that prevents excessive stroking loads from occurring while in operation. This paper highlights some of the design and operating aspects and the testing of this energy absorber.
Metal-shearing energy absorber
NASA Technical Reports Server (NTRS)
Fay, R. J.; Wittrock, E. P.
1971-01-01
Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.
Leaf absorbance and photosynthesis
NASA Technical Reports Server (NTRS)
Schurer, Kees
1994-01-01
The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.
NASA Astrophysics Data System (ADS)
Ferruzzo Correa, Diego Paolo; Wulff, Claudia; Piqueira, José Roberto Castilho
2015-05-01
In recent years there has been an increasing interest in studying time-delayed coupled networks of oscillators since these occur in many real life applications. In many cases symmetry patterns can emerge in these networks, as a consequence a part of the system might repeat itself, and properties of this subsystem are representative of the dynamics on the whole phase space. In this paper an analysis of the second order N-node time-delay fully connected network is presented which is based on previous work: synchronous states in time-delay coupled periodic oscillators: a stability criterion. Correa and Piqueira (2013), for a 2-node network. This study is carried out using symmetry groups. We show the existence of multiple eigenvalues forced by symmetry, as well as the existence of Hopf bifurcations. Three different models are used to analyze the network dynamics, namely, the full-phase, the phase, and the phase-difference model. We determine a finite set of frequencies ω , that might correspond to Hopf bifurcations in each case for critical values of the delay. The Sn map is used to actually find Hopf bifurcations along with numerical calculations using the Lambert W function. Numerical simulations are used in order to confirm the analytical results. Although we restrict attention to second order nodes, the results could be extended to higher order networks provided the time-delay in the connections between nodes remains equal.
NASA Astrophysics Data System (ADS)
Wang, Qiang; Xiao, Meng; Liu, Hui; Zhu, Shining; Chan, C. T.
2016-01-01
The Zak phase labels the topological property of one-dimensional Bloch bands. Here we propose a scheme and experimentally measure the Zak phase in a photonic system. The Zak phase of a bulk band is related to the topological properties of the two band gaps sandwiching this band, which in turn can be inferred from the existence or absence of an interface state. Using a reflection spectrum measurement, we determined the existence of interface states in the gaps and then obtained the Zak phases. The knowledge of Zak phases can also help us predict the existence of interface states between a metasurface and a photonic crystal. By manipulating the property of the metasurface, we can further tune the excitation frequency and the polarization of the interface state.
Visible light broadband perfect absorbers
NASA Astrophysics Data System (ADS)
Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O.
2016-03-01
The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.
Heaving buoys, point absorbers and arrays.
Falnes, Johannes; Hals, Jørgen
2012-01-28
Absorption of wave energy may be considered as a phenomenon of interference between incident and radiated waves generated by an oscillating object; a wave-energy converter (WEC) that displaces water. If a WEC is very small in comparison with one wavelength, it is classified as a point absorber (PA); otherwise, as a 'quasi-point absorber'. The latter may be a dipole-mode radiator, for instance an immersed body oscillating in the surge mode or pitch mode, while a PA is so small that it should preferably be a source-mode radiator, for instance a heaving semi-submerged buoy. The power take-off capacity, the WEC's maximum swept volume and preferably also its full physical volume should be reasonably matched to the wave climate. To discuss this matter, two different upper bounds for absorbed power are applied in a 'Budal diagram'. It appears that, for a single WEC unit, a power capacity of only about 0.3 MW matches well to a typical offshore wave climate, and the full physical volume has, unfortunately, to be significantly larger than the swept volume, unless phase control is used. An example of a phase-controlled PA is presented. For a sizeable wave-power plant, an array consisting of hundreds, or even thousands, of mass-produced WEC units is required. PMID:22184661
Berry's phase observed in the ordered state of Fe(Se,S)
NASA Astrophysics Data System (ADS)
Kasahara, Shigeru; Yamashita, T.; Shimoyama, Y.; Watashige, T.; Matsuda, Y.; Béard, J.; Nardone, M.; Knafo, W.; Watson, M. D.; Davis, N. R.; Coldea, A. I.; Suzuki, M.; Arita, R.; Ikeda, H.; Shibauchi, T.
Among iron-based superconductors, FeSe offers a unique platform in that it exhibits a nematically ordered phase without long-range magnetic ordering. Several experiments have shown that the low-temperature Fermi surface of FeSe consists only of very small, shallow pockets [1-3]. Tuning the ground state via isoelectronic chemical substitution provides an ideal way to solve the puzzles regarding the nematic ordering in this material. Here, by using ultra-high magnetic fields up to ~ 90 T, we report observations of Shubnikov-de Haas (SdH) oscillations in isoelectronically substituted Fe(Se,S). For the smallest pocket of ~ 0 . 2 % of the Brillouin-zone, we observe non-zero π Berry's phase shift in the SdH oscillations. Our results indicate presence of Dirac cone, which would be a key to understand the mechanism of the nematic ordering in this system.
Qubit phase space: SU(n) coherent-state P representations
NASA Astrophysics Data System (ADS)
Barry, D. W.; Drummond, P. D.
2008-11-01
We introduce a phase-space representation for qubits and spin models. The technique uses an SU(n) coherent-state basis and can equally be used for either static or dynamical simulations. We review previously known definitions and operator identities, and show how these can be used to define an off-diagonal, positive phase-space representation analogous to the positive- P function. As an illustration of the phase-space method, we use the example of the Ising model, which has exact solutions for the finite-temperature canonical ensemble in two dimensions. We show how a canonical ensemble for an Ising model of arbitrary structure can be efficiently simulated using SU(2) or atomic coherent states. The technique utilizes a transformation from a canonical (imaginary-time) weighted simulation to an equivalent unweighted real-time simulation. The results are compared to the exactly soluble two-dimensional case. We note that Ising models in one, two, or three dimensions are potentially achievable experimentally as a lattice gas of ultracold atoms in optical lattices. The technique is not restricted to canonical ensembles or to Ising-like couplings. It is also able to be used for real-time evolution and for systems whose time evolution follows a master equation describing decoherence and coupling to external reservoirs. The case of SU(n) phase space is used to describe n -level systems. In general, the requirement that time evolution be stochastic corresponds to a restriction to Hamiltonians and master equations that are quadratic in the group generators or generalized spin operators.
NASA Astrophysics Data System (ADS)
Liu, Zhao; Vaezi, Abolhassan; Lee, Kyungmin; Kim, Eun-Ah
2015-08-01
Recent theoretical insights into the possibility of non-Abelian phases in ν =2 /3 fractional quantum Hall states revived the interest in the numerical phase diagram of the problem. We investigate the effect of various kinds of two-body interlayer couplings on the (330) bilayer state and exactly solve the Hamiltonian for up to 14 electrons on sphere and torus geometries. We consider interlayer tunneling, short-ranged repulsive/attractive pseudopotential interactions, and Coulomb repulsion. We find a 6-fold ground-state degeneracy on the torus when the interlayer hollow-core interaction is dominant. To identify the topological nature of this phase we measure the orbital-cut entanglement spectrum, quasihole counting, topological entanglement entropy, and wave-function overlap. Comparing the numerical results to the theoretical predictions, we interpret this 6-fold ground-state degeneracy phase to be the non-Abelian bilayer Fibonacci state.
The ultimate chrome absorber in photomask making
NASA Astrophysics Data System (ADS)
Hashimoto, Masahiro; Iwashita, Hiroyuki; Kominato, Atsushi; Shishido, Hiroaki; Ushida, Masao; Mitsui, Hideaki
2008-05-01
193nm-immersion lithography is the most promising technology for 32nm-node device fabrication. A new Cr absorber (TFC) for 193-nm attenuated phase-shift blanks was developed to meet the photomask requirements without any additional process step, such as hardmask etching. TFC was introduced with a design concept of the vertical profile for shorter etching time, the over etching time reduction. As a result, the dry-etching time was dramatically improved by more than 20% shorter than the conventional Cr absorber (TF11) without any process changes. We confirmed that 150nm-resist thickness was possible by TFC. The 32nm technology-node requirement is fully supported by TFC with thinner CAR, such as resolution and CD performance.
Litynski, John T; Plasynski, Sean; McIlvried, Howard G; Mahoney, Christopher; Srivastava, Rameshwar D
2008-01-01
This paper reviews the Validation Phase (Phase II) of the Department of Energy's Regional Carbon Sequestration Partnerships initiative. In 2003, the U.S. Department of Energy created a nationwide network of seven Regional Carbon Sequestration Partnerships (RCSP) to help determine and implement the technology, infrastructure, and regulations most appropriate to promote carbon sequestration in different regions of the nation. The objectives of the Characterization Phase (Phase I) were to characterize the geologic and terrestrial opportunities for carbon sequestration; to identify CO(2) point sources within the territories of the individual partnerships; to assess the transportation infrastructure needed for future deployment; to evaluate CO(2) capture technologies for existing and future power plants; and to identify the most promising sequestration opportunities that would need to be validated through a series of field projects. The Characterization Phase was highly successful, with the following achievements: established a national network of companies and professionals working to support sequestration deployment; created regional and national carbon sequestration atlases for the United States and portions of Canada; evaluated available and developing technologies for the capture of CO(2) from point sources; developed an improved understanding of the permitting requirements that future sequestration activities will need to address as well as defined the gap in permitting requirements for large scale deployment of these technologies; created a raised awareness of, and support for, carbon sequestration as a greenhouse gas (GHG) mitigation option, both within industry and among the general public; identified the most promising carbon sequestration opportunities for future field tests; and established protocols for project implementation, accounting, and management. Economic evaluation was started and is continuing and will be a factor in project selection. During the
Canonical deformations of surfaces of equilibrium states in thermodynamic phase space
Jurkowski
2000-08-01
Deformations of submanifolds of thermodynamic equilibrium states introduced by continuous contact maps on a phase-space manifold are considered in terms of the geometrical formulation of thermodynamics. The notion of a contact Hamiltonian is recalled in order to give some possible physical interpretations of such a function in terms of statistical quantities describing initial and deformed systems. Using contact flows we propose a very efficient method for constructing continuous families of thermodynamic systems. A few examples show the possible advantages of using contact Hamiltonians. PMID:11088641
Low-temperature solid-state phase transformations in 2H silicon carbide.
NASA Technical Reports Server (NTRS)
Powell, J. A.; Will, H. A.
1972-01-01
Study of the phase transformations taking place in 2H SiC single crystals at temperatures as low as 400 C. Some crystals transformed to a structure with one-dimensional disorder along the crystal c axis. Others transformed to a faulted cubic/6H structure. The transformation is time and temperature dependent, and is greatly enhanced by dislocations. The transformation takes place by means of a slip process perpendicular to the c axis. Cubic SiC crystals were observed to undergo a solid-state transformation above 1400 C.
Low-temperature solid-state phase transformations in 2H silicon carbide
NASA Technical Reports Server (NTRS)
Will, H. A.; Powell, J. A.
1972-01-01
Single crystals of 2H SiC were observed to undergo phase transformations at temperatures as low as 400 C. Some 2H crystals transformed to a structure with one-dimensional disorder along the crystal c axis. Others transformed to a faulted cubic/6H structure. The transformation is time and temperature dependent and is greatly enhanced by dislocations. Observations indicate that the transformation takes place by means of a slip process perpendicular to the c axis. Cubic SiC crystals were observed to undergo a solid state transformation above 1400 C.
NASA Astrophysics Data System (ADS)
Miškovičová, Ivica; Hell, Natalie; Hanke, Manfred; Nowak, Michael A.; Pottschmidt, Katja; Schulz, Norbert S.; Grinberg, Victoria; Duro, Refiz; Madej, Oliwia K.; Lohfink, Anne M.; Rodriguez, Jérôme; Cadolle Bel, Marion; Bodaghee, Arash; Tomsick, John A.; Lee, Julia C.; Brown, Gregory V.; Wilms, Jörn
2016-05-01
Accretion onto the black hole in the system HDE 226868/Cygnus X-1 is powered by the strong line-driven stellar wind of the O-type donor star. We study the X-ray properties of the stellar wind in the hard state of Cyg X-1, as determined using data from the Chandra High Energy Transmission Gratings. Large density and temperature inhomogeneities are present in the wind, with a fraction of the wind consisting of clumps of matter with higher density and lower temperature embedded in a photoionized gas. Absorption dips observed in the light curve are believed to be caused by these clumps. This work concentrates on the non-dip spectra as a function of orbital phase. The spectra show lines of H-like and He-like ions of S, Si, Na, Mg, Al, and highly ionized Fe (Fe xvii-Fe xxiv). We measure velocity shifts, column densities, and thermal broadening of the line series. The excellent quality of these five observations allows us to investigate the orbital phase-dependence of these parameters. We show that the absorber is located close to the black hole. Doppler shifted lines point at a complex wind structure in this region, while emission lines seen in some observations are from a denser medium than the absorber. The observed line profiles are phase-dependent. Their shapes vary from pure, symmetric absorption at the superior conjunction to P Cygni profiles at the inferior conjunction of the black hole.
Thermal equations of state of the {alpha}, {beta}, and {omega} phases of zirconium
Zhao Yusheng; Zhang Jianzhong; Pantea, Cristian; Qian Jiang; Daemen, Luke L.; Rigg, Paulo A.; Hixson, Robert S.; Gray, George T. III; Yang Yunpeng; Wang Liping; Wang Yanbin; Uchida, Takeyuki
2005-05-01
We have conducted synchrotron x-ray diffraction studies on high purity zirconium metal at pressures (P) up to 17 GPa and temperatures (T) up to 973 K. Unit cell volumes (V) were derived from the refinements of x-ray diffraction data for the {alpha}, {beta}, and {omega} phases of zirconium and fitted to a Birch-Murnaghan equation of state with the pressure derivative of the bulk modulus, K{sub 0}{sup '}, fixed at 4.0. The derived thermoelastic parameters for {alpha} zirconium are isothermal bulk modulus K{sub 0}=92(3) GPa, temperature derivative of bulk modulus ({partial_derivative}K/{partial_derivative}T){sub P}=-2.3(8)x10{sup -2} GPa/K, volumetric thermal expansivity {alpha}{sub T}=a+bT with a=1.5({+-}0.8)x10{sup -5} K{sup -1} and b=1.7({+-}1.4)x10{sup -8} K{sup -2}, and the pressure derivative of thermal expansion ({partial_derivative}{alpha}/{partial_derivative}P){sub T}=-2.7(9)x10{sup -6} GPa{sup -1} K{sup -1}. For the {beta} phase we obtained an isothermal bulk modulus of K{sub T}=66(3) GPa at 973 K and a unit-cell volume of V(973 K)=47.7(3) A{sup 3} at ambient pressure. For the {omega} zirconium we obtained K{sub 0}=90(5) GPa. Within the experimental errors, the K{sub 0} values we determined for the {alpha} and {omega} phases and volumetric thermal expansion for the {alpha} phase are in agreement with previous experimental results, whereas all other thermoelastic parameters represent the first determinations for the three crystalline phases of zirconium metal.
Thermal Equations of State of the alpha, beta, and omega Phases of Zirconium
Zhao,Y.; Zhang, J.; Pantea, C.; Qian, J.; Daemen, L.; Rigg, P.; Hixson, R.; Gray, III, G.; Yang, Y.; et al.
2005-01-01
We have conducted synchrotron x-ray diffraction studies on high purity zirconium metal at pressures (P) up to 17 GPa and temperatures (T) up to 973 K. Unit cell volumes (V) were derived from the refinements of x-ray diffraction data for the {alpha}, {beta}, and {omega} phases of zirconium and fitted to a Birch-Murnaghan equation of state with the pressure derivative of the bulk modulus, K{sub 0}{prime}, fixed at 4.0. The derived thermoelastic parameters for {alpha} zirconium are isothermal bulk modulus K{sub 0}=92(3) GPa, temperature derivative of bulk modulus ({partial_derivative}K/{partial_derivative}T)P=-2.3(8)x10{sup -2} GPa/K, volumetric thermal expansivity {alpha}{sub T=a+bT} with a=1.5({+-}0.8)x10{sup -5} K{sup -1} and b=1.7({+-}1.4)x10{sup -8} K{sup -2}, and the pressure derivative of thermal expansion ({partial_derivative}{alpha}/{partial_derivative}P)T=-2.7(9)x10{sup -6} GPa{sup -1} K{sup -1}. For the {beta} phase we obtained an isothermal bulk modulus of K{sub T}=66(3) GPa at 973 K and a unit-cell volume of V(973 K)=47.7(3) Angstroms{sup 3} at ambient pressure. For the {omega} zirconium we obtained K{sub 0}=90(5) GPa. Within the experimental errors, the K0 values we determined for the {alpha} and {omega} phases and volumetric thermal expansion for the {alpha} phase are in agreement with previous experimental results, whereas all other thermoelastic parameters represent the first determinations for the three crystalline phases of zirconium metal.
Phase transition and equation of state of paratellurite (TeO2) under high pressure
NASA Astrophysics Data System (ADS)
Liu, Xun; Mashimo, Tsutomu; Kawai, Nobuaki; Sekine, Toshimori; Zeng, Zhaoyi; Zhou, Xianming
2016-07-01
The Hugoniot data for TeO2 single crystals were obtained for pressures up to ∼85 GPa along both the <100> (a-axis) and <001> (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun or two-stage light gas gun. The Hugoniot-elastic limit of TeO2 was determined to be 3.3–4.3 GPa along the c-axes. The shock velocity (U s) versus particle velocity (U p) relation for TeO2 shows a kink around U p = 1.0 km s‑1, which suggests a phase transition completes at ∼26 ± 2 GPa. The Hugoniot relations of the low and high pressure phase are given by U s = 3.13(5) + 1.10(6)U p for U p < 1.0 km s‑1 and U s = 2.73(9) + 1.49(5)U p for U p > 1.0 km s‑1, respectively. First-principles geometry optimizations based on the generalized gradient approximation after Perdew, Burke and Ernzerhof method were also performed on TeO2. It suggested that a continuous structure distortion occurs up to 22 GPa, and the lattice parameters b and c abruptly increase and decrease at 22 GPa, respectively, indicating a first-order phase transition to the cotunnite structure phase. The equation of state of the cotunnite phase TeO2 is discussed based on the experimental and simulation results.
Equation of state and phase behavior of a propane-tetrafluoroethane mixture
NASA Astrophysics Data System (ADS)
Vasserman, A. A.; Mal'chevsky, V. P.
2012-09-01
A general equation of state was derived for a propane-tetrafluoroethane mixture in a form representing the free Helmholtz energy of a mixture as the function of density, temperature, and composition. Coefficients of equation were determined according to data on the density of the mixture and assuming the equilibrium condition of phases. The equation describes the thermodynamic properties of vapor and liquid in the temperature range from 255 to 400 K under pressures up to 6 MPa. The thermodynamic behavior of the mixture at the saturation state was analyzed. It is established that the difference between the temperatures of saturated vapor and of liquid on isobars for four compositions did not exceed 1.8 K.
Microwave Reflectometry Measurements of Flux States of a dc SQUID Phase Qubit
NASA Astrophysics Data System (ADS)
Cooper, B. K.; Lewis, R. M.; Dutta, S. K.; Palomaki, T. A.; Przybysz, Anthony; Kwon, H.; Paik, Hanhee; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.
2008-03-01
We examine microwave reflectometry readout of a dc SQUID phase qubit. Our device is a Nb/AlOx/Nb SQUID fabricated by Hypres with loop inductance of 1.3 nH and symmetric junction critical currents of approximately 5 μA. The SQUID is current and flux biased, with one junction used as the qubit and the other used to provide isolation. The isolation junction is shunted by a large capacitor to depress its plasma frequency to about 1.5 GHz. This frequency can be shifted by flux-induced circulating current in the SQUID loop, allowing us to determine which flux state we are in by making reflectometry measurements of the resonant behavior of the isolation junction. The utility of this measurement for qubit state readout is discussed.
Spin glass state and enhanced spiral phase in doped delafossite oxide CuCr O2
NASA Astrophysics Data System (ADS)
Yan, Z. R.; Qin, M. H.; Dong, S.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.
2016-07-01
In this paper, we study the doping effects on the magnetic states of CuCr O2 based on the classical frustrated spin model [13aa Lin et al., Phys. Rev. B 89, 220405(R) (2014), 10.1103/PhysRevB.89.220405]. Several experimental observations can be well reproduced by the Monte Carlo simulations of the modified spin models. Our paper suggests that the disorder induced by V/Al doping cooperating with the frustration in the system may contribute to the emergence of the spin glass state. Furthermore, the hole doping by M g2 + substituting C r3 + enhances the quantum fluctuations and bond disorder which modulate the biquadratic exchanges and in turn results in the promotion of the spiral phase, consistent with the experimental report.
Absorbent product to absorb fluids. [for collection of human wastes
NASA Technical Reports Server (NTRS)
Dawn, F. S.; Correale, J. V. (Inventor)
1982-01-01
A multi-layer absorbent product for use in contact with the skin to absorb fluids is discussed. The product utilizes a water pervious facing layer for contacting the skin, overlayed by a first fibrous wicking layer, the wicking layer preferably being of the one-way variety in which fluid or liquid is moved away from the facing layer. The product further includes a first container section defined by inner and outer layer of a water pervious wicking material between which is disposed a first absorbent mass. A second container section defined by inner and outer layers between which is disposed a second absorbent mass and a liquid impermeable/gas permeable layer. Spacesuit applications are discussed.
The Potential Economic Impact of Electricity Restructuring in the State of Oklahoma: Phase II Report
Hadley, SW
2001-10-30
Because of the recent experiences of several states undergoing restructuring (e.g., higher prices, greater volatility, lower reliability), concerns have been raised in states currently considering restructuring as to whether their systems are equally vulnerable. Factors such as local generation costs, transmission constraints, market concentration, and market design can all play a role in the success or failure of the market. These factors along with the mix of generation capacity supplying the state will influence the relative prices paid by consumers. The purpose of this project is to provide a model and process to evaluate the potential price and economic impacts of restructuring the Oklahoma electric industry. The Phase I report concentrated on providing an analysis of the Oklahoma system in the near-term, using only present generation resources and customer demands. This Phase II study analyzed the Oklahoma power market in 2010, incorporating the potential of new generation resources and customer responses. Five key findings of this Phase II were made: (1) Projected expansion in generating capacity exceeds by over 3,000 MW the demands within the state plus the amount that could be exported with the current transmission system. (2) Even with reduced new plant construction, most new plants could lose money (although residential consumers would see lower rates) unless they have sufficient market power to raise their prices without losing significant market share (Figure S-1). (3) If new plants can raise prices to stay profitable, existing low-cost coal and hydro plants will have very high profits. Average prices to customers could be 5% to 25% higher than regulated rates (Figure S-1). If the coal and hydro plants are priced at cost-based rates (through long-term contracts or continued regulation) while all other plants use market-based rates then prices are lower. (4) Customer response to real-time prices can lower the peak capacity requirements by around 9
Determination of neutron absorbed doses in lithium aluminates.
Delfín Loya, A; Carrera, L M; Ureña-Núñez, F; Palacios, O; Bosch, P
2003-04-01
Lithium-based ceramics have been proposed as tritium breeders for fusion reactors. The lithium aluminate (gamma phase) seems to be thermally and structurally stable, the damages produced by neutron irradiation depend on the absorbed dose. A method based on the measurement of neutron activation of foils through neutron capture has been developed to obtain the neutron absorbed dose in lithium aluminates irradiated in the thermal column facility and in the fixed irradiation system of a Triga Mark III Nuclear Reactor. PMID:12672632
Corrections of Hayes Equation of State for Phase Transform under Dynamic Loading
NASA Astrophysics Data System (ADS)
Chong, Tao
Abstract: The experimental results of iron under ramp wave and shock compression are simulated with Hayes equation of state (EOS) for phase transition. The calculated results are consistent with the experimental data under shock, and don't agree well with the data under ramp wave loading. The reason for the problem is that the bulk modulus in Hayes model is constant (i.e., Bulk sound speed is constant). The sound speed corresponds to the slope of the Rayleigh line when materials leap from the initial state to the final state under shock loading, therefore, the bulk modulus can be considered as a constant. However, under ramp loading, material from initial to the final state is consecutive, and the bulk modulus is not a constant any more but a function of pressure and temperature. The bulk modulus of Hayes EOS is corrected with Murnaghan EOS, and the corrected Hayes EOS is applies to simulate the experimental results. The results show that the calculated data agree well with the experimental data under both shock and ramp wave loadings. . I hope you give me an oral presentation, otherwise I might not be able to attend the meeting.
Stabilizing the phase of superpositions of cat states in a cavity using real-time feedback
NASA Astrophysics Data System (ADS)
Ofek, N.; Petrenko, A.; Heeres, R.; Reinhold, P.; Liu, Y.; Leghtas, Z.; Vlastakis, B.; Frunzio, L.; Jiang, Liang; Mirrahimi, M.; Devoret, M. H.; Schoelkopf, R. J.
In a superconducting cQED architecture, a hardware efficient quantum error correction (QEC) scheme exists, called the cat code, which maps a qubit onto superpositions of cat states in a superconducting resonator, by mapping the occurrence of errors, or single photon jumps, onto unitary rotations of the encoded state. By tracking the parity of the encoded state, we can count the number of photon jumps and are able to apply a correcting unitary transformation. However, the situation is complicated by the fact that photon jumps do not commute with the deterministic anharmonic time evolution of a resonator state, or Kerr, inherited by the resonator from its coupling to a Josephson junction. As predicted in, a field in the resonator will inherit an overall phase θ = KT in IQ space each time a photon jumps that is proportional to the Kerr K and the time T at which the jump occurs. Here I will present how we can track the errors in real time, take them into account together with the time they occur and make it possible to stabilize the qubit information. Please place my talk right after the talk of Andrei Petrenko.
Ground-state phase structure of the spin-1/2 anisotropic planar pyrochlore.
Li, P H Y; Bishop, R F
2015-09-30
We study the zero-temperature ground-state (GS) properties of the spin-1/2 anisotropic planar pyrochlore, using the coupled cluster method (CCM) implemented to high orders of approximation. The system comprises a J 1-J 2 model on the checkerboard lattice, with isotropic Heisenberg interactions of strength J 1 between all nearest-neighbour pairs of spins on the square lattice, and of strength J 2 between half of the next-nearest-neighbour pairs (in the checkerboard pattern). We calculate results for the GS energy and average local GS on-site magnetization, using various antiferromagnetic classical ground states as CCM model states. We also give results for the susceptibility of one of these states against the formation of crossed-dimer valence-bond crystalline (CDVBC) ordering. The complete GS phase diagram is presented for arbitrary values of the frustration parameter k≡J2/J1, and when each of the exchange couplings can take either sign. PMID:26348836
First-order optimal linear and nonlinear detuning of centrifugal pendulum vibration absorbers
NASA Astrophysics Data System (ADS)
Mayet, J.; Ulbrich, H.
2015-01-01
Centrifugal pendulum vibration absorbers are used to attenuate steady-state torsional vibrations in rotating and reciprocating machines. In most practical implementations, a set of multiple absorbers is symmetrically arranged on a rotor. Typically, each absorber mass is bifilar suspended, which allows the absorber mass to be moved along a prescribed path. Previous studies have considered how to determine absorber paths in order to obtain absorbers with amplitude-independent frequency known as tautochronic absorbers. It is known that a tautochronic absorber is highly desirable if only one absorber is installed on the rotor. However, in most applications multiple interacting absorbers are installed and as a result symmetry-induced nonlinear instabilities or localization caused by relative imperfections among the absorbers may occur. An effective strategy to avoid such situations is to perturb the tautochronic tuning which has been confirmed in practice and by previous theoretical investigations. This paper presents an approach for detuning a recently developed general tautochronic absorber design. The general design makes it possible to consider a wide class of tautochronic absorbers, e.g. absorbers without bifilar suspensions. The intent of this paper is to extend the existing tautochronic design guideline to non-tautochronic designs. As a result, different absorber designs can be addressed by one uniform theoretical approach, and existing absorber designs are included as special cases. Former studies on detuning of bifilar tautochronic absorbers use a one-parameter family of curves on which the absorber mass rides. Here, however, the detuning is not restricted to a one-parameter family of curves, which makes it possible to either optimize system performance or to avoid asynchronous absorber responses. In the case of synchronously responding equal absorbers, a necessary condition for optimal performance is derived analytically. Further, it is shown that asynchronous
Skyrme random-phase-approximation description of lowest Kπ=2γ+ states in axially deformed nuclei
NASA Astrophysics Data System (ADS)
Nesterenko, V. O.; Kartavenko, V. G.; Kleinig, W.; Kvasil, J.; Repko, A.; Jolos, R. V.; Reinhard, P.-G.
2016-03-01
The lowest quadrupole γ -vibrational Kπ=2+ states in axially deformed rare-earth (Nd, Sm, Gd, Dy, Er, Yb, Hf, W) and actinide (U) nuclei are systematically investigated within the separable random-phase-approximation (SRPA) based on the Skyrme functional. The energies Eγ and reduced transition probabilities B (E 2 ) of 2γ+ states are calculated with the Skyrme forces SV-bas and SkM*. The energies of two-quasiparticle configurations forming the SRPA basis are corrected by using the pairing blocking effect. This results in a systematic downshift of Eγ by 0.3-0.5 MeV and thus in a better agreement with the experiment, especially in Sm, Gd, Dy, Hf, and W regions. For other isotopic chains, a noticeable overestimation of Eγ and too weak collectivity of 2γ+ states still persist. It is shown that domains of nuclei with low and high 2γ+ collectivity are related to the structure of the lowest two-quasiparticle states and conservation of the Nilsson selection rules. The description of 2γ+ states with SV-bas and SkM* is similar in light rare-earth nuclei but deviates in heavier nuclei. However SV-bas much better reproduces the quadrupole deformation and energy of the isoscalar giant quadrupole resonance. The accuracy of SRPA is justified by comparison with exact RPA. The calculations suggest that a further development of the self-consistent calculation schemes is needed for a systematic satisfactory description of the 2γ+ states.
High pressure-temperature phase diagram and equation of state of titanium
NASA Astrophysics Data System (ADS)
Dewaele, Agnès; Stutzmann, Vincent; Bouchet, Johann; Bottin, François; Occelli, Florent; Mezouar, Mohamed
2015-04-01
The high pressure-temperature behavior of titanium has been studied with x-ray diffraction in resistively heated and laser-heated diamond anvil cells up to 200 GPa and ˜3500 K. The stability fields of α -Ti ,ω -Ti ,β -Ti ,γ -Ti , and δ -Ti have been determined in this range. γ -Ti and δ -Ti , which had been evidenced earlier under nonhydrostatic compression, are also observed in helium pressure transmitting medium. Equation-of-state parameters are proposed for α -Ti and ω -Ti at 300 K, and β -Ti at high temperature. The stability fields of the α ,ω ,γ , and δ phases are also studied using the projector-augmented wave method based on density-functional theory. Using the relevant core radius to avoid overlapping between atomic spheres, and relaxing cells and atomic positions, we show that all those phases have a stability domain at 0 K. We explain why γ -Ti and δ -Ti were calculated to be unstable in earlier works. In addition, a new phase, called δ'-Ti, which is a distortion of δ -Ti , is predicted to form between 80 and 120 GPa and below ≃200 K.
Phase control of squeezed vacuum states of light in gravitational wave detectors.
Dooley, K L; Schreiber, E; Vahlbruch, H; Affeldt, C; Leong, J R; Wittel, H; Grote, H
2015-04-01
Quantum noise will be the dominant noise source for the advanced laser interferometric gravitational wave detectors currently under construction. Squeezing-enhanced laser interferometers have been recently demonstrated as a viable technique to reduce quantum noise. We propose two new methods of generating an error signal for matching the longitudinal phase of squeezed vacuum states of light to the phase of the laser interferometer output field. Both provide a superior signal to the one used in previous demonstrations of squeezing applied to a gravitational-wave detector. We demonstrate that the new signals are less sensitive to misalignments and higher order modes, and result in an improved stability of the squeezing level. The new signals also offer the potential of reducing the overall rms phase noise and optical losses, each of which would contribute to achieving a higher level of squeezing. The new error signals are a pivotal development towards realizing the goal of 6 dB and more of squeezing in advanced detectors and beyond. PMID:25968662
Phase based venous suppression in resting-state BOLD GE-fMRI.
Curtis, Andrew T; Hutchison, R Matthew; Menon, Ravi S
2014-10-15
Resting-state functional MRI (RS-fMRI) is a widely used method for inferring connectivity between brain regions or nodes. As with task-based fMRI, the spatial specificity of the connectivity maps can be distorted by the strong biasing effect of the BOLD signal in macroscopic veins. In RS-fMRI this effect is exacerbated by the temporal coherences of physiological origin between large veins that are widely distributed in the brain. In gradient echo based EPI, used for the vast majority of RS-fMRI, macroscopic veins that carry BOLD-related changes exhibit a strong phase response. This allows for post-processing identification and removal of venous signals using a phase regressor technique. Here, we employ this approach to suppress macrovascular venous contributions in high-field whole-brain RS-fMRI data sets, resulting in significant changes to both the spatial localization of the networks and the correlations between the network nodes. These effects were observed at both the individual and group analysis level, suggesting that venous contamination is a confounding factor for RS-fMRI studies even at relatively low image resolutions. Suppression of the macrovascular signal using the phase regression approach may therefore help to better identify, delineate, and interpret the true structure of large-scale brain networks. PMID:24907484
A concise model for mixed-mode phase transformations in the solid state
Sietsma, Jilt; Zwaag, Sybrand van der
2004-08-16
Using a Zener-like approach, the character of partitioning mixed-mode phase transformations in the solid state is shown to be governed by a single parameter Z. The parameter is proportional to the diffusivity of the partitioning element and the area-to-volume ratio of the growing grain, and inversely proportional to the interface mobility and to the driving pressure per unit of concentration difference. A value Z=0 implies a diffusion-controlled transformation, for Z{yields}{infinity} the transformation is interface-controlled. The significance of the parameter, both for the character of the transformation and for the transformation kinetics, is shown by the example of the austenite-to-ferrite transformation in iron-carbon alloys. A remarkable outcome is that all phase transformations start as an interface-controlled transformation and with proceeding growth of the newly forming phase gradually shift towards diffusion control. This gradual change in transformation character is accompanied by a gradual decrease of the interface velocity.
A Simple State-Determined Model Reproduces Entrainment and Phase-Locking of Human Walking
Ahn, Jooeun; Hogan, Neville
2012-01-01
Theoretical studies and robotic experiments have shown that asymptotically stable periodic walking may emerge from nonlinear limit-cycle oscillators in the neuro-mechanical periphery. We recently reported entrainment of human gait to periodic mechanical perturbations with two essential features: 1) entrainment occurred only when the perturbation period was close to the original (preferred) walking period, and 2) entrainment was always accompanied by phase locking so that the perturbation occurred at the end of the double-stance phase. In this study, we show that a highly-simplified state-determined walking model can reproduce several salient nonlinear limit-cycle behaviors of human walking: 1) periodic gait that is 2) asymptotically stable; 3) entrainment to periodic mechanical perturbations only when the perturbation period is close to the model's unperturbed period; and 4) phase-locking to locate the perturbation at the end of double stance. Importantly, this model requires neither supra-spinal control nor an intrinsic self-sustaining neural oscillator such as a rhythmic central pattern generator. Our results suggest that several prominent limit-cycle features of human walking may stem from simple afferent feedback processes without significant involvement of supra-spinal control or a self-sustaining oscillatory neural network. PMID:23152761
NASA Astrophysics Data System (ADS)
He, Yuan-Yao; Wu, Han-Qing; You, Yi-Zhuang; Xu, Cenke; Meng, Zi Yang; Lu, Zhong-Yi
2016-03-01
It is expected that the interplay between nontrivial band topology and strong electron correlation will lead to very rich physics. Thus a controlled study of the competition between topology and correlation is of great interest. Here, employing large-scale quantum Monte Carlo simulations, we provide a concrete example of the Kane-Mele-Hubbard model on an AA-stacking bilayer honeycomb lattice with interlayer antiferromagnetic interaction. Our simulation identified several different phases: a quantum spin Hall insulator (QSH), an x y -plane antiferromagnetic Mott insulator, and an interlayer dimer-singlet insulator. Most importantly, a bona fide topological phase transition between the QSH and the dimer-singlet insulators, purely driven by the interlayer antiferromagnetic interaction, is found. At the transition, the spin and charge gap of the system close while the single-particle excitations remain gapped, which means that this transition has no mean-field analog and it can be viewed as a transition between bosonic symmetry-protected topological (SPT) states. At one special point, this transition is described by a (2 +1 )d O (4 ) nonlinear sigma model with exact S O (4 ) symmetry and a topological term at exactly Θ =π . The relevance of this work towards more general interacting SPT states is discussed.
Decoherence of odd compass states in the phase-sensitive amplifying/dissipating environment
NASA Astrophysics Data System (ADS)
Dodonov, V. V.; Valverde, C.; Souza, L. S.; Baseia, B.
2016-08-01
We study the evolution of odd compass states (specific superpositions of four coherent states), governed by the standard master equation with phase-sensitive amplifying/attenuating terms, in the presence of a Hamiltonian describing a parametric degenerate linear amplifier. Explicit expressions for the time-dependent Wigner function are obtained. The time of disappearance of the so called "sub-Planck structures" is calculated using the negative value of the Wigner function at the origin of phase space. It is shown that this value rapidly decreases during a short "conventional interference degradation time" (CIDT), which is inversely proportional to the size of quantum superposition, provided the anti-Hermitian terms in the master equation are of the same order (or stronger) as the Hermitian ones (governing the parametric amplification). The CIDT is compared with the final positivization time (FPT), when the Wigner function becomes positive. It appears that the FPT does not depend on the size of superpositions, moreover, it can be much bigger in the amplifying media than in the attenuating ones. Paradoxically, strengthening the Hamiltonian part results in decreasing the CIDT, so that the CIDT almost does not depend on the size of superpositions in the asymptotical case of very weak reservoir coupling. We also analyze the evolution of the Mandel factor, showing that for some sets of parameters this factor remains significantly negative, even when the Wigner function becomes positive.
Bona fide interaction-driven topological phase transition in correlated SPT states
NASA Astrophysics Data System (ADS)
Meng, Zi Yang; He, Yuan-Yao; Wu, Han-Qing; You, Yi-Zhuang; Xu, Cenke; Lu, Zhong-Yi
It is expected the interplay between non-trivial band topology and strong electron correlation will lead to very rich physics. Thus a controlled study of the competition between topology and correlation is of great interest. Here, employing large-scale quantum Monte Carlo simulations, we provide a concrete example of the Kane-Mele-Hubbard model on an AA stacking bilayer honeycomb lattice with inter-layer antiferromagnetic interaction. Our simulation identified several different phases: a quantum spin-Hall insulator (QSH), a xy-plane antiferromagnetic Mott insulator (xy-AFM) and an inter-layer dimer-singlet insulator (dimer-singlet). Most importantly, a bona fide topological phase transition between the QSH and the dimer-singlet insulators, purely driven by the inter-layer antiferromagnetic interaction is found. At the transition, the spin and charge gap of the system close while the single-particle excitations remain gapped, which means that this transition has no mean field analogue and it can be viewed as a transition between bosonic SPT states. At one special point, this transition is described by a (2+1)d O(4) nonlinear sigma model with exact SO(4) symmetry, and a topological term at theta=p. Relevance of this work towards more general interacting SPT states is discussed.
Phase sensitivity of two nonlinear interferometers with inputting entangled coherent states
NASA Astrophysics Data System (ADS)
Wei, Chao-Ping; Xiao-Yu, Hu; Ya-Fei, Yu; Zhi-Ming, Zhang
2016-04-01
We investigate the phase sensitivity of the SU(1,1) interfereometer [SU(1,1)I] and the modified Mach–Zehnder interferometer (MMZI) with the entangled coherent states (ECS) as inputs. We consider the ideal case and the situations in which the photon losses are taken into account. We find that, under ideal conditions, the phase sensitivity of both the MMZI and the SU(1,1)I can beat the shot-noise limit (SNL) and approach the Heisenberg limit (HL). In the presence of photon losses, the ECS can beat the coherent and squeezed states as inputs in the SU(1,1)I, and the MMZI is more robust against internal photon losses than the SU(1,1)I. Project supported by the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91121023), the National Natural Science Foundation of China (Grant Nos. 11574092, 61378012, and 60978009), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20124407110009), the National Basic Research Program of China (Grant Nos. 2011CBA00200 and 2013CB921804), and the Program for Innovative Research Team in University (Grant No. IRT1243).
Numerical prediction of steady-state detonation properties of condensed-phase explosives.
Cengiz, F; Ulas, A
2009-12-30
Within the scope of this study, a computer code named BARUT-X has been developed to calculate the detonation properties of C-H-N-O based condensed-phase explosives using the Chapman-Jouguet (C-J) theory. Determination of the detonation properties is performed in chemical equilibrium and steady-state conditions. Unlike other codes in the literature which use steepest descent optimization method, BARUT-X uses a nonlinear optimization code based on Generalized Reduced Gradient algorithm to compute the equilibrium composition of the detonation products. This optimization code provides a higher level of robustness of the solutions and global optimum determination efficiency. The Becker-Kistiakowsky-Wilson's (BKW) equation of state (EOS) is applied to the high-density gaseous detonation products at high pressures. BARUT-X uses RDX, TNT, BKWR, and BKWN set of constants in the BKW EOS. In addition, the Cowan-Fickett's EOS is applied for the compressible solid carbon in the detonation products. The calculated detonation properties for several condensed-phase explosives by BARUT-X have been compared with those computed by EXPLO5 and FORTRAN BKW codes as well as the experimental data in terms of detonation velocity and detonation pressure. Satisfactory agreement is obtained from these comparisons. PMID:19747772
NASA Astrophysics Data System (ADS)
Yoshii, Ryosuke; Takada, Satoshi; Tsuchiya, Shunji; Marmorini, Giacomo; Hayakawa, Hisao; Nitta, Muneto
2015-12-01
We find the angular Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states (or the twisted kink crystals) in which a phase and an amplitude of a pair potential modulate simultaneously in a quasi-one-dimensional superconducting ring with a static Zeeman magnetic field applied on the ring and static Aharonov-Bohm magnetic flux penetrating the ring. The superconducting ring with magnetic flux produces a persistent current, whereas the Zeeman split of Fermi energy results in the spatial modulation of the pair potential. We show that these two magnetic fields stabilize the FFLO phase in a large parameter region of the magnetic fields. We further draw the phase diagram with the two kinds of first-order phase transitions; one corresponds to phase slips separating the Aharonov-Bohm magnetic flux, and the other separates the number of peaks of the pair amplitude for the Zeeman magnetic field.
Properties of meso-Erythritol; phase state, accommodation coefficient and saturation vapour pressure
NASA Astrophysics Data System (ADS)
Emanuelsson, Eva; Tschiskale, Morten; Bilde, Merete
2016-04-01
Introduction Saturation vapour pressure and the associated temperature dependence (enthalpy ΔH), are key parameters for improving predictive atmospheric models. Generally, the atmospheric aerosol community lack experimentally determined values of these properties for relevant organic aerosol compounds (Bilde et al., 2015). In this work we have studied the organic aerosol component meso-Erythritol. Methods Sub-micron airborne particles of meso-Erythritol were generated by nebulization from aqueous solution, dried, and a mono disperse fraction of the aerosol was selected using a differential mobility analyser. The particles were then allowed to evaporate in the ARAGORN (AaRhus Atmospheric Gas phase OR Nano particle) flow tube. It is a temperature controlled 3.5 m long stainless steel tube with an internal diameter of 0.026 m (Bilde et al., 2003, Zardini et al., 2010). Changes in particle size as function of evaporation time were determined using a scanning mobility particle sizer system. Physical properties like air flow, temperature, humidity and pressure were controlled and monitored on several places in the setup. The saturation vapour pressures were then inferred from the experimental results in the MATLAB® program AU_VaPCaP (Aarhus University_Vapour Pressure Calculation Program). Results Following evaporation, meso-Erythriol under some conditions showed a bimodal particle size distribution indicating the formation of particles of two different phase states. The issue of physical phase state, along with critical assumptions e.g. the accommodation coefficient in the calculations of saturation vapour pressures of atmospheric relevant compounds, will be discussed. Saturation vapour pressures from the organic compound meso-Erythritol will be presented at temperatures between 278 and 308 K, and results will be discussed in the context of atmospheric chemistry. References Bilde, M. et al., (2015), Chemical Reviews, 115 (10), 4115-4156. Bilde, M. et. al., (2003
Space Evaporator Absorber Radiator (SEAR) for Thermal Storage on Manned Spacecraft
NASA Technical Reports Server (NTRS)
Izenson, Michael G.; Chen, Weibo; Chepko, Ariane; Bue, Grant; Quinn, Gregory
2014-01-01
Future manned exploration spacecraft will need to operate in challenging thermal environments. State-of the- art technology for active thermal control relies on sublimating water ice and venting the vapor overboard in very hot environments. This approach can lead to large loss of water and a significant mass penalty for the spacecraft. This paper describes an innovative thermal control system that uses a Space Evaporator Absorber Radiator (SEAR) to control spacecraft temperatures in highly variable environments without venting water. SEAR uses heat pumping and energy storage by LiCl/water absorption to enable effective cooling during hot periods and regeneration during cool periods. The LiCl absorber technology has the potential to absorb over 800 kJ per kg of system mass, compared to phase change heat sink systems that typically achieve approx. 50 kJ/kg. The optimal system is based on a trade-off between the mass of water saved and extra power needed to regenerate the LiCl absorber. This paper describes analysis models and the predicted performance and optimize the size of the SEAR system, estimated size and mass of key components, and power requirements for regeneration. We also present a concept design for an ISS test package to demonstrate operation of a subscale system in zero gravity.
NASA Astrophysics Data System (ADS)
Meyer, Jessica; Krämer, Martina; Afchine, Armin; Gallagher, Martin; Dorsey, James; Brown, Phil; Woolley, Alan; Bierwirth, Eike; Ehrlich, Andre; Wendisch, Manfred; Gehrmann, Martin
2013-04-01
The influence of mixed-phase clouds on the radiation budget of the earth is largely unknown. One of the key parameters to determine mixed-phase cloud radiative properties however is the fraction of ice particles and liquid droplets in these clouds. The separate detection of liquid droplets and ice crystals especially in the small cloud particle size range below 50 µm remains challenging though. Here, we present airborne NIXE-CAPS mixed-phase cloud particle measurements observed in mid-latitude and Arctic low-level mixed-phase clouds during the COALESC field campaign in 2011 and the Arctic field campaign VERDI in 2012. NIXE-CAPS (Novel Ice EXpEriment - Cloud and Aerosol Particle Spectrometer, manufactured by DMT) is a cloud particle spectrometer which measures the cloud particle number, size as well as their phase for each cloud particle in the diameter range 0.6 to 945 µm. The common understanding in mixed-phase cloud research is that liquid droplets and ice crystals in the same cloud volume are rather sparse, but instead either liquid droplets or ice crystals are present. However, recently published model studies (e.g. Korolev, A. & Field, P., The effect of dynamics on mixed-phase clouds: Theoretical considerations. J. Atmos. Sci. 65, 66-86, 2008) indicate that a cloud state containing both liquid droplets and ice crystals can be kept up by turbulence. Indeed, our particle by particle analyses of the observed mixed-phase clouds during COALESC and VERDI indicate that the real mixed-phase state is rather common in the atmosphere. The spatial distribution of the mixed-phase ice fraction and the size of the droplets and ice crystals however vary substantially from case to case. The latter parameters seem to be influenced not only by concentration of ice nuclei but also - to a large degree - by cloud dynamics.
ERIC Educational Resources Information Center
Nicolaides, Cleanthes A.; Constantoudis, Vasilios
2009-01-01
In Planck's model of the harmonic oscillator (HO) a century ago, both the energy and the phase space were quantized according to epsilon[subscript n] = nhv, n = 0, 1, 2..., and [double integral]dp[subscript x] dx = h. By referring to just these two relations, we show how the adoption of "cycle-averaged phase-space states" (CAPSSs) leads to the…
Countercurrent flow absorber and desorber
Wilkinson, William H.
1984-01-01
Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.
Packed Alumina Absorbs Hypergolic Vapors
NASA Technical Reports Server (NTRS)
Thomas, J. J.; Mauro, D. M.
1984-01-01
Beds of activated alumina effective as filters to remove hypergolic vapors from gas streams. Beds absorb such substances as nitrogen oxides and hydrazines and may also absorb acetylene, ethylene, hydrogen sulfide, benzene, butadiene, butene, styrene, toluene, and xoylene. Bed has no moving parts such as pumps, blowers and mixers. Reliable and energy-conservative. Bed readily adapted to any size from small portable units for use where little vapor release is expected to large stationary units for extensive transfer operations.
Countercurrent flow absorber and desorber
Wilkinson, W.H.
1984-10-16
Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.
Naikaew, Atittaya; Prajongtat, Pongthep; Lux-Steiner, Martha Ch.; Dittrich, Thomas; Arunchaiya, Marisa
2015-06-08
Modulated surface photovoltage (SPV) spectra have been correlated with the phase composition in layers of CH{sub 3}NH{sub 3}PbI{sub 3} (MAPbI{sub 3}) prepared from MAI and PbCl{sub 2} and annealed at 100 °C. Depending on the annealing time, different compositions of MAPbI{sub 3}, MAPbCl{sub 3}, MACl, PbI{sub 2}, and an un-identified phase were found. It has been demonstrated that evaporation of MAI and HI is crucial for the development of electronic states in MAPbI{sub 3} and that only the appearance and evolution of the phase PbI{sub 2} has an influence on electronic states in MAPbI{sub 3}. With ongoing annealing, (i) a transition from p- to n-type doping was observed with the appearance of PbI{sub 2}, (ii) shallow acceptor states were distinguished and disappeared in n-type doped MAPbI{sub 3}, and (iii) a minimum of the SPV response related to deep defect states was found at the transition from p- to n-type doping. The results are discussed with respect to the further development of highly efficient and stable MAPbI{sub 3} absorbers for solar cells.
NASA Astrophysics Data System (ADS)
Jamal, Wasifa; Das, Saptarshi; Maharatna, Koushik; Pan, Indranil; Kuyucu, Doga
2015-09-01
Degree of phase synchronization between different Electroencephalogram (EEG) channels is known to be the manifestation of the underlying mechanism of information coupling between different brain regions. In this paper, we apply a continuous wavelet transform (CWT) based analysis technique on EEG data, captured during face perception tasks, to explore the temporal evolution of phase synchronization, from the onset of a stimulus. Our explorations show that there exists a small set (typically 3-5) of unique synchronized patterns or synchrostates, each of which are stable of the order of milliseconds. Particularly, in the beta (β) band, which has been reported to be associated with visual processing task, the number of such stable states has been found to be three consistently. During processing of the stimulus, the switching between these states occurs abruptly but the switching characteristic follows a well-behaved and repeatable sequence. This is observed in a single subject analysis as well as a multiple-subject group-analysis in adults during face perception. We also show that although these patterns remain topographically similar for the general category of face perception task, the sequence of their occurrence and their temporal stability varies markedly between different face perception scenarios (stimuli) indicating toward different dynamical characteristics for information processing, which is stimulus-specific in nature. Subsequently, we translated these stable states into brain complex networks and derived informative network measures for characterizing the degree of segregated processing and information integration in those synchrostates, leading to a new methodology for characterizing information processing in human brain. The proposed methodology of modeling the functional brain connectivity through the synchrostates may be viewed as a new way of quantitative characterization of the cognitive ability of the subject, stimuli and information integration
Mechanically stretchable and tunable metamaterial absorber
NASA Astrophysics Data System (ADS)
Zhang, Fuli; Feng, Shuqi; Qiu, Kepeng; Liu, Zijun; Fan, Yuancheng; Zhang, Weihong; Zhao, Qian; Zhou, Ji
2015-03-01
In this letter, we present experimental demonstration of a mechanically stretchable and tunable metamaterial absorber composed of dielectric resonator stacked on a thin conductive rubber layer. A near unity absorption is observed due to strong local field confinement around magnetic Mie resonance of dielectric resonator. Furthermore, the interspacing between unit cells is modulated dynamically under uniaxial stress. Owing to the decreases of longitudinal coupling between neighboring unit cells, the resonant absorption peak is reversibly tuned by 410 MHz, as the stain varies up to 180% along H field direction. On the contrary, the resonant absorption state is nearly independent on strain variation when external stress is applied along E field direction, due to the weak transverse interplaying. The mechanically tunable metamaterial absorber featured by flexibility paves a way forwards for actual application.
Uribe-Patarroyo, Nestor; Alvarez-Herrero, Alberto; Belenguer, Tomas
2010-05-15
We propose the use of a phase-diversity technique to estimate the orbital angular momentum (OAM) superposition state of an ensemble of photons that passes through an optical system, proceeding from an extended object. The phase-diversity technique permits the estimation of the optical transfer function (OTF) of an imaging optical system. As the OTF is derived directly from the wave-front characteristics of the observed light, we redefine the phase-diversity technique in terms of a superposition of OAM states. We test this new technique experimentally and find coherent results among different tests, which gives us confidence in the estimation of the photon ensemble state. We find that this technique not only allows us to estimate the square of the amplitude of each OAM state, but also the relative phases among all states, thus providing complete information about the quantum state of the photons. This technique could be used to measure the OAM spectrum of extended objects in astronomy or in an optical communication scheme using OAM states. In this sense, the use of extended images could lead to new techniques in which the communication is further multiplexed along the field.
The equation of state of the Pmmn phase of NiSi
Lord, Oliver T.; Thomson, Andrew R.; Wann, Elizabeth T. H.; Wood, Ian G.; Dobson, David P.; Vocadlo, Lidunka
2015-01-01
The equation of state of the orthorhombic phase of NiSi with Pmmn symmetry has been determined at room temperature from synchrotron-based X-ray diffraction measurements of its lattice parameters, made in a diamond anvil cell. Measurements were performed up to 44 GPa, using Ne as the pressure medium and Au as the pressure standard. The resulting pressure–volume (P–V) data have been fitted with a Birch–Murnaghan equation of state of third order to yield V 0 = 11.650 (7) Å3 atom−1, K 0 = 162 (3) GPa and K 0′ = 4.6 (2). In addition, P–V data have been collected on Ni53Si47 in the B20 structure using both Ne and He as the pressure media and Cu and Au as the pressure standards, also to 44 GPa. A fit using the same Birch–Murnaghan equation of state of third order yields V 0 = 11.364 (6) Å3 atom−1, K 0 = 171 (4) GPa and K 0′ = 5.5 (3). PMID:26664346
Is solid state lighting ready for the incandescent lamp phase-out?
NASA Astrophysics Data System (ADS)
Narendran, Nadarajah
2011-10-01
To encourage energy-efficient light sources, many governments around the globe have introduced legislation to phase out the incandescent lamp for general illumination. The United States enacted the Energy Independence and Security Act of 2007 that introduced minimum efficiency standards for lighting that will eliminate some incandescent lamps in the range of 40 W to 100 W by 2014. This begs the question: Is solid-state lighting ready to handle the incandescent phaseout? There is no doubt today that LED technology has advanced to a stage where it can cater to many lighting applications, including A-lamp replacements up to 60 W. However, several challenges must still be addressed before white LED based A-lamp replacements are adopted broadly in the general lighting market. The LED lighting community is actively seeking answers to many of the technical and market challenges. This paper discusses the current state of LED lighting technology, where it is in terms of performance, the challenges to be overcome, and the considerations needed if LED lighting is to succeed in the market for incandescent replacement lamps.
Bina, Matteo; Allevi, Alessia; Bondani, Maria; Olivares, Stefano
2016-01-01
Phase estimation represents a crucial challenge in many fields of Physics, ranging from Quantum Metrology to Quantum Information Processing. This task is usually pursued by means of interferometric schemes, in which the choice of the input states and of the detection apparatus is aimed at minimizing the uncertainty in the estimation of the relative phase between the inputs. State discrimination protocols in communication channels with coherent states also require the monitoring of the optical phase. Therefore, the problem of phase estimation is relevant to face the issue of coherent states discrimination. Here we consider a quasi-optimal Kennedy-like receiver, based on the interference of two coherent signals, to be discriminated, with a reference local oscillator. By means of the Bayesian processing of a small amount of data drawn from the outputs of the shot-by-shot discrimination protocol, we demonstrate the achievement of the minimum uncertainty in phase estimation, also in the presence of uniform phase noise. Moreover, we show that the use of photon-number resolving detectors in the receiver improves the phase-estimation strategy, especially with respect to the usually employed on/off detectors. From the experimental point of view, this comparison is realized by employing hybrid photodetectors. PMID:27189140
Bina, Matteo; Allevi, Alessia; Bondani, Maria; Olivares, Stefano
2016-01-01
Phase estimation represents a crucial challenge in many fields of Physics, ranging from Quantum Metrology to Quantum Information Processing. This task is usually pursued by means of interferometric schemes, in which the choice of the input states and of the detection apparatus is aimed at minimizing the uncertainty in the estimation of the relative phase between the inputs. State discrimination protocols in communication channels with coherent states also require the monitoring of the optical phase. Therefore, the problem of phase estimation is relevant to face the issue of coherent states discrimination. Here we consider a quasi-optimal Kennedy-like receiver, based on the interference of two coherent signals, to be discriminated, with a reference local oscillator. By means of the Bayesian processing of a small amount of data drawn from the outputs of the shot-by-shot discrimination protocol, we demonstrate the achievement of the minimum uncertainty in phase estimation, also in the presence of uniform phase noise. Moreover, we show that the use of photon-number resolving detectors in the receiver improves the phase-estimation strategy, especially with respect to the usually employed on/off detectors. From the experimental point of view, this comparison is realized by employing hybrid photodetectors. PMID:27189140
NASA Astrophysics Data System (ADS)
Bina, Matteo; Allevi, Alessia; Bondani, Maria; Olivares, Stefano
2016-05-01
Phase estimation represents a crucial challenge in many fields of Physics, ranging from Quantum Metrology to Quantum Information Processing. This task is usually pursued by means of interferometric schemes, in which the choice of the input states and of the detection apparatus is aimed at minimizing the uncertainty in the estimation of the relative phase between the inputs. State discrimination protocols in communication channels with coherent states also require the monitoring of the optical phase. Therefore, the problem of phase estimation is relevant to face the issue of coherent states discrimination. Here we consider a quasi-optimal Kennedy-like receiver, based on the interference of two coherent signals, to be discriminated, with a reference local oscillator. By means of the Bayesian processing of a small amount of data drawn from the outputs of the shot-by-shot discrimination protocol, we demonstrate the achievement of the minimum uncertainty in phase estimation, also in the presence of uniform phase noise. Moreover, we show that the use of photon-number resolving detectors in the receiver improves the phase-estimation strategy, especially with respect to the usually employed on/off detectors. From the experimental point of view, this comparison is realized by employing hybrid photodetectors.
Metastable morphotropic phase boundary state in the multiferroic BiFeO3-PbTiO3
NASA Astrophysics Data System (ADS)
Kothai, V.; Prasath Babu, R.; Ranjan, Rajeev
2013-09-01
Temperature-time study of the magnetoelectric multiferroic (1-x)BiFeO3-(x)PbTiO3 by x-ray and electron diffraction on the reported morphotropic phase boundary (MPB) compositions revealed that this MPB does not correspond to the equilibrium state. The MPB like state is rather of metastable nature and arise due to kinetic arrest of metastable rhombohedral (R3c) phase, along with the equilibrium tetragonal (P4mm) phase. The life time of the metastable R3c nuclei is very sensitive to composition and temperature, and nearly diverges at x → 0.27. The MPB like state appears only if the system is cooled before the metastable R3c nuclei could vanish. These findings resolve the long standing controversy with regard to seemingly erratic phase formation behaviour reported by different groups and provides a rational basis for developing genuine equilibrium MPB compositions in this system for better piezoelectric properties.
GAS-PHASE ELECTRONIC SPECTRA OF POLYACETYLENE CATIONS: RELEVANCE OF HIGHER EXCITED STATES
Rice, C. A.; Rudnev, V.; Dietsche, R.; Maier, J. P.
2010-07-15
Transitions to higher electronic states of polyacetylene cations (HC{sub 2n}H{sup +}, n = 4, 5, 6) have been measured in the gas phase at {approx}20 K. The absorption spectra were obtained using a resonant two-color, two-photon fragmentation technique in an ion trap, allowing a direct comparison between laboratory and astrophysical data. The purpose was to investigate the relevance of such transitions to astronomical observations because the general expectation is that the bands could be too broad due to fast intramolecular processes. It is shown that the origin bands are still narrow enough (1-10 cm{sup -1}) to be considered, especially as the higher-lying transitions often possess large oscillator strengths.
Clarke, Patrick J.; Collins, Robert J.; Dunjko, Vedran; Andersson, Erika; Jeffers, John; Buller, Gerald S.
2012-01-01
Digital signatures are frequently used in data transfer to prevent impersonation, repudiation and message tampering. Currently used classical digital signature schemes rely on public key encryption techniques, where the complexity of so-called ‘one-way' mathematical functions is used to provide security over sufficiently long timescales. No mathematical proofs are known for the long-term security of such techniques. Quantum digital signatures offer a means of sending a message, which cannot be forged or repudiated, with security verified by information-theoretical limits and quantum mechanics. Here we demonstrate an experimental system, which distributes quantum signatures from one sender to two receivers and enables message sending ensured against forging and repudiation. Additionally, we analyse the security of the system in some typical scenarios. Our system is based on the interference of phase-encoded coherent states of light and our implementation utilizes polarization-maintaining optical fibre and photons with a wavelength of 850 nm. PMID:23132024
Density of states at disorder-induced phase transitions in a multichannel Majorana wire
NASA Astrophysics Data System (ADS)
Rieder, Maria-Theresa; Brouwer, Piet W.
2014-11-01
An N -channel spinless p -wave superconducting wire is known to go through a series of N topological phase transitions upon increasing the disorder strength. Here, we show that at each of those transitions the density of states shows a Dyson singularity ν (ɛ ) ∝ɛ-1|lnɛ| -3 , whereas ν (ɛ ) ∝ɛ|α |-1 has a power-law singularity for small energies ɛ away from the critical points. Using the concept of "superuniversality" [Gruzberg et al., Phys. Rev. B 71, 245124 (2005), 10.1103/PhysRevB.71.245124], we are able to relate the exponent α to the wire's transport properties at zero energy and, hence, to the mean free path l and the superconducting coherence length ξ .
Structure-phase states evolution in rails during a long operation
Peregudov, Oleg Gromov, Victor Morozov, Konstantin Alsaraeva, Krestina Semina, Olga; Ivanov, Yurii
2015-10-27
By methods of scanning and transmission electron microscopy the transformation regularities of structure-phase states, defect substructure, fracture surface of rail surface layer up to 10 mm deep in process of long-term operation (passed tonnage of gross weight 1000 mln tons) were revealed. It has been shown that the surface layer ∼20 μm in thickness has a multiphase, submicro- and nanocrystalline structure and it contains micropores and microcracks. The increased density of bend extinction contours at 2 mm depth from the tread contact surface was noted. The analysis of structure morphological constituents and internal stress fields, created by intra- and interphase boundaries after long operation was carried out. It was shown that the maximum amplitude of stress fields was formed on the interphase boundary the globular cementite particle–matrix. The evaluation of stress fields was done.
Phase space dynamics and control of the quantum particles associated to hypergraph states
NASA Astrophysics Data System (ADS)
Berec, Vesna
2015-05-01
As today's nanotechnology focus becomes primarily oriented toward production and manipulation of materials at the subatomic level, allowing the performance and complexity of interconnects where the device density accepts more than hundreds devices on a single chip, the manipulation of semiconductor nanostructures at the subatomic level sets its prime tasks on preserving and adequate transmission of information encoded in specified (quantum) states. The presented study employs the quantum communication protocol based on the hypergraph network model where the numerical solutions of equations of motion of quantum particles are associated to vertices (assembled with device chip), which follow specific controllable paths in the phase space. We address these findings towards ultimate quest for prediction and selective control of quantum particle trajectories. In addition, presented protocols could represent valuable tool for reducing background noise and uncertainty in low-dimensional and operationally meaningful, scalable complex systems.
Space Evaporator Absorber Radiator (SEAR) for Thermal Storage on Manned Spacecraft
NASA Technical Reports Server (NTRS)
Izenson, Michael G.; Chen, Weibo; Chepko, Ariane; Bue, Grant; Quinn, Gregory
2015-01-01
Future manned exploration spacecraft will need to operate in challenging thermal environments. State-of-the-art technology for active thermal control relies on sublimating water ice and venting the vapor overboard in very hot environments, and or heavy phase change material heat exchangers for thermal storage. These approaches can lead to large loss of water and a significant mass penalties for the spacecraft. This paper describes an innovative thermal control system that uses a Space Evaporator Absorber Radiator (SEAR) to control spacecraft temperatures in highly variable environments without venting water. SEAR uses heat pumping and energy storage by LiCl/water absorption to enable effective cooling during hot periods and regeneration during cool periods. The LiCl absorber technology has the potential to absorb over 800 kJ per kg of system mass, compared to phase change heat sink systems that typically achieve approx. 50 kJ/kg. This paper describes analysis models to predict performance and optimize the size of the SEAR system, estimated size and mass of key components, and an assessment of potential mass savings compared with alternative thermal management approaches. We also describe a concept design for an ISS test package to demonstrate operation of a subscale system in zero gravity.
Synthesis and equation of state of high pressure phase of chromium-bearing spinel
NASA Astrophysics Data System (ADS)
Shieh, S. R.; Khan, T.; Prescher, C.; Prakapenka, V.; MI, Z.
2015-12-01
Chromium-bearing spinel (Mg,Fe)Cr2O4 can be found in the Earth's crust, upper mantle, and even in meteorites. Mantle derived chromium-bearing spinel suggests that its high pressure phase may be existing at deep mantle but however its high pressure elastic property is not well understood yet. In situ synchrotron X-ray diffraction studies of magnesiochromite and chromite using the laser-heated diamond anvil cell were performed at GSECARS, Advanced Photon Source, to explore their high pressure phases and elastic property. Our results on magnesiochromite showed dissociation of MgCr2O4 to Cr2O3+MgO at ~15 GPa and to modified Ludwigite (mLd)-type Mg2Cr2O5+Cr2O3 below and above ~1500 K, respectively. At above 20 GPa, only a single phase CaTi2O4-type structure of MgCr2O4 was observed at 1400-2000 K. Pressure-volume data of CaTi2O4 type structure of MgCr2O4 fitted to Birch-Murnaghan equation of state yield zero-pressure volume (V0) = 264.4(8) Å3, bulk modulus (K0) = 185.4(4) GPa, and pressure derivative (K0') = 4; and mLd-type Mg2Cr2O5 yields: V0 = 338.9(8) Å3, K0 = 186.5(6) GPa, K0' = 4. For CaTi2O4 type structure of natural chromite, our fitted P-V data show V0 = 261(1) Å3, K0 = 175.4(2) GPa, and K0' = 4.
Probing Phase Coherence Via Density of States for Strongly Correlated Excitons
NASA Astrophysics Data System (ADS)
Apinyan, V.; Kopeć, T. K.
2015-03-01
We present the calculation of the coherent spectral functions and density of states (DOS) for excitonic systems in the frame of the three-dimensional extended Falicov-Kimball model. Using gage-invariant U(1) transformation to the usual fermions, we represent the electron operator as a fermion attached to the U(1) phase-flux tube. The emergent bosonic gage field, related to the phase variables, is crucial for the Bose-Einstein condensation (BEC) of excitons. Employing the path-integral formalism, we manipulate the bosonic and fermionic degrees of freedom to obtain the effective actions related to fermionic and bosonic sectors. Considering the normal and anomalous excitonic Green functions, we calculate the spectral functions, which have the forms of convolutions in the reciprocal space between bosonic and fermionic counterparts. For the fermionic incoherent part of the DOS, we have found the strong evidence of the hybridization gap in DOS spectra. Furthermore, considering Bogoliubov coherence mechanism, we calculate the coherent DOS spectra. For the coherent normal fermionic DOS, there is no hybridization gap found in the system due to strong coherence effects and phase stiffness. The similar behavior is observed also for the condensate part of the anomalous excitonic DOS spectra. We show that for small values of the Coulomb interaction the fermionic DOS exhibits a Bardeen-Cooper-Schrieffer (BCS)-like double-peak structure. In the BEC region of the BCS-BEC crossover, the double-peak structure disappears totally for both: coherent and incoherent DOS spectra. We discuss also the temperature dependence of DOS functions.
Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds
NASA Astrophysics Data System (ADS)
Ebert, M.; Worringen, A.; Benker, N.; Mertes, S.; Weingartner, E.; Weinbruch, S.
2011-03-01
During an intensive campaign at the high alpine research station Jungfraujoch, Switzerland, in February/March 2006 ice particle residuals within mixed-phase clouds were sampled using the Ice-counterflow virtual impactor (Ice-CVI). Size, morphology, chemical composition, mineralogy and mixing state of the ice residual and the interstitial (i.e., non-activated) aerosol particles were analyzed by scanning and transmission electron microscopy. Ice nuclei (IN) were identified from the significant enrichment of particle groups in the ice residual (IR) samples relative to the interstitial aerosol. In terms of number lead-bearing particles are enriched by a factor of approximately 25, complex internal mixtures with silicates or metal oxides as major components by a factor of 11, and mixtures of secondary aerosol and carbonaceous material (C-O-S particles) by a factor of 2. Other particle groups (sulfates, sea salt, Ca-rich particles, external silicates) observed in the ice-residual samples cannot be assigned unambiguously as IN. Between 9 and 24% of all IR are Pb-bearing particles. Pb was found as major component in around 10% of these particles (PbO, PbCl2). In the other particles, Pb was found as some 100 nm sized agglomerates consisting of 3-8 nm sized primary particles (PbS, elemental Pb). C-O-S particles are present in the IR at an abundance of 17-27%. The soot component within these particles is strongly aged. Complex internal mixtures occur in the IR at an abundance of 9-15%. Most IN identified at the Jungfraujoch station are internal mixtures containing anthropogenic components (either as main or minor constituent), and it is concluded that admixture of the anthropogenic component is responsible for the increased IN efficiency within mixed phase clouds. The mixing state appears to be a key parameter for the ice nucleation behaviour that cannot be predicted from the sole knowledge of the main component of an individual particle.
NASA Astrophysics Data System (ADS)
Pan, Weichun; Kolomeisky, Anatoly B.; Vekilov, Peter G.
2005-05-01
Nucleation of ordered solid phases of proteins triggers numerous phenomena in laboratory, industry, and in healthy and sick organisms. Recent simulations and experiments with protein crystals suggest that the formation of an ordered crystalline nucleus is preceded by a disordered high-density cluster, akin to a droplet of high-density liquid that has been observed with some proteins; this mechanism allowed a qualitative explanation of recorded complex nucleation kinetics curves. Here, we present a simple phenomenological theory that takes into account intermediate high-density metastable states in the nucleation process. Nucleation rate data at varying temperature and protein concentration are reproduced with high fidelity using literature values of the thermodynamic and kinetic parameters of the system. Our calculations show that the growth rate of the near-critical and supercritical ordered clusters within the dense intermediate is a major factor for the overall nucleation rate. This highlights the role of viscosity within the dense intermediate for the formation of the ordered nucleus. The model provides an understanding of the action of additives that delay or accelerate nucleation and presents a framework within which the nucleation of other ordered protein solid phases, e.g., the sickle cell hemoglobin polymers, can be analyzed.
Pathways through equilibrated states with coexisting phases for gas hydrate formation
Malolepsza, Edyta; Keyes, Tom
2015-12-01
Under ambient conditions, water freezes to either hexagonal ice or a hexagonal/cubic composite ice. The presence of hydrophobic guest molecules introduces a competing pathway: gas hydrate formation, with the guests in clathrate cages. Here, the pathways of the phase transitions are sought as sequences of states with coexisting phases, using a generalized replica exchange algorithm designed to sample them in equilibrium, avoiding nonequilibrium processes. For a dilute solution of methane in water under 200 atm, initializing the simulation with the full set of replicas leads to methane trapped in hexagonal/cubic ice, while gradually adding replicas with decreasing enthalpy produces the initial steps of hydrate growth. Once a small amount of hydrate is formed, water rearranges to form empty cages, eventually transforming the remainder of the system to metastable β ice, a scaffolding for hydrates. It is suggested that configurations with empty cages are reaction intermediates in hydrate formation when more guest molecules are available. Furthermore, free energy profiles show that methane acts as a catalyst reducing the barrier for β ice versus hexagonal/cubic ice formation.
Pathways through Equilibrated States with Coexisting Phases for Gas Hydrate Formation.
Małolepsza, Edyta; Keyes, Tom
2015-12-31
Under ambient conditions, water freezes to either hexagonal ice or a hexagonal/cubic composite ice. The presence of hydrophobic guest molecules introduces a competing pathway: gas hydrate formation, with the guests in clathrate cages. Here, the pathways of the phase transitions are sought as sequences of states with coexisting phases, using a generalized replica exchange algorithm designed to sample them in equilibrium, avoiding nonequilibrium processes. For a dilute solution of methane in water under 200 atm, initializing the simulation with the full set of replicas leads to methane trapped in hexagonal/cubic ice, while gradually adding replicas with decreasing enthalpy produces the initial steps of hydrate growth. Once a small amount of hydrate is formed, water rearranges to form empty cages, eventually transforming the remainder of the system to metastable β ice, a scaffolding for hydrates. It is suggested that configurations with empty cages are reaction intermediates in hydrate formation when more guest molecules are available. Free energy profiles show that methane acts as a catalyst reducing the barrier for β ice versus hexagonal/cubic ice formation. PMID:26624929
SESAME 96171, a three-phase equation of state for CeO_{2}
Chisolm, Eric D.
2014-07-08
This report describes an earlier version of an equation of state (EOS) for cerium (IV) oxide, CeO_{2}. This work has been superseded by a newer version that is described in LA-UR-14-24689. Everything from this report needed to understand the new version is included in the new report. I have constructed SESAME 96171, an EOS for cerium (IV) oxide that includes two solid phases and the liquid. Unlike its immediate predecessor, this EOS is valid over a larger range in pressure due to including the extra phase. I have described the process of constructing and testing the EOS, emphasizing its continuity with the previous EOS and the modifications needed for the new frame-work. The comparison with data is good, but is still limited by the same issues with nuclear models that were present in the previous work. The remaining significant issue is the comparison of the crystal-density EOS with experimental porous Hugoniot data, which may require using more sophisticated model to represent porosity, as discussed in the previous report.
Pathways through equilibrated states with coexisting phases for gas hydrate formation
Malolepsza, Edyta; Keyes, Tom
2015-12-01
Under ambient conditions, water freezes to either hexagonal ice or a hexagonal/cubic composite ice. The presence of hydrophobic guest molecules introduces a competing pathway: gas hydrate formation, with the guests in clathrate cages. Here, the pathways of the phase transitions are sought as sequences of states with coexisting phases, using a generalized replica exchange algorithm designed to sample them in equilibrium, avoiding nonequilibrium processes. For a dilute solution of methane in water under 200 atm, initializing the simulation with the full set of replicas leads to methane trapped in hexagonal/cubic ice, while gradually adding replicas with decreasing enthalpy produces themore » initial steps of hydrate growth. Once a small amount of hydrate is formed, water rearranges to form empty cages, eventually transforming the remainder of the system to metastable β ice, a scaffolding for hydrates. It is suggested that configurations with empty cages are reaction intermediates in hydrate formation when more guest molecules are available. Furthermore, free energy profiles show that methane acts as a catalyst reducing the barrier for β ice versus hexagonal/cubic ice formation.« less
The Warm Absorber of the Seyfert Galaxy NGC 5548
NASA Astrophysics Data System (ADS)
Andrade, M.; Krongold, Y.; Elvis, M.; Nicastro, F.; Binette, L.; Brickhouse, N.
2008-04-01
We present a spectral analysis of the X-ray Chandraof the Seyfert 1 Galaxy NGC 5548. The warm absorber present in this object was modeled with the code PHASE. We detected two different outflow velocity systems in this source. One of the absorbing systems has outflow velocity of -1091+/-63 km s(-1) and the other of -568+/-49 km s(-1) . Each system required two absorption components with different ionization level to fit the observed features. Each velocity system may consist of a multi-phase medium.
Two-Phase ({gamma},{alpha}) Equation of State for Cerium and Features of its Dynamic Compression
Yelkin, V. M.; Kozlov, E. A.; Kakshina, E. V.; Moreva, Yu. S.
2006-07-28
The unusual thermodynamic properties of cerium result from features in the narrow 4f-zone whose electrons are subdivided into localized and delocalized subsystems. In this paper the model of pseudo-binary solid solutions allowing for two different electronic states is applied to construct the thermodynamically complete two-phase equation of state for cerium. The parameters of the model were fitted to describe the thermodynamic data obtained in the static experiments with high-purity cerium. This equation of state was used to analyze wave structures realized under dynamic compression with regard to the equilibrium ({gamma},{alpha}) phase transition.
NASA Astrophysics Data System (ADS)
Curty, Marcos; Tamaki, Kiyoshi; Moroder, Tobias; Gómez-Sousa, Hipólito
2009-04-01
In this paper we present limitations imposed by sequential attacks on the maximal distance achievable by a differential-phase-shift (DPS) quantum key distribution (QKD) protocol with weak coherent pulses. Specifically, we compare the performance of two possible sequential attacks against DPS QKD where Eve realizes, respectively, optimal unambiguous state discrimination of Alice's signal states, and optimal unambiguous discrimination of the relative phases between consecutive signal states. We show that the second eavesdropping strategy provides tighter upper bounds for the security of a DPS QKD scheme than the former one.
NASA Astrophysics Data System (ADS)
Zhang, Kai; Nusran, N. M.; Slezak, B. R.; Gurudev Dutt, M. V.
2016-05-01
While it is often thought that the geometric phase is less sensitive to fluctuations in the control fields, a very general feature of adiabatic Hamiltonians is the unavoidable dynamic phase that accompanies the geometric phase. The effect of control field noise during adiabatic geometric quantum gate operations has not been probed experimentally, especially in the canonical spin qubit system that is of interest for quantum information. We present measurement of the Berry phase and carry out adiabatic geometric phase gate in a single solid-state spin qubit associated with the nitrogen-vacancy center in diamond. We manipulate the spin qubit geometrically by careful application of microwave radiation that creates an effective rotating magnetic field, and observe the resulting Berry phase signal via spin echo interferometry. Our results show that control field noise at frequencies higher than the spin echo clock frequency causes decay of the quantum phase, and degrades the fidelity of the geometric phase gate to the classical threshold after a few (∼10) operations. This occurs inspite of the geometric nature of the state preparation, due to unavoidable dynamic contributions. We have carried out systematic analysis and numerical simulations to study the effects of the control field noise and imperfect driving waveforms on the quantum phase gate.
Statistical-mechanical equation of state for nonpolar fluids: Prediction of phase boundaries
NASA Astrophysics Data System (ADS)
Tao, Fu-Ming; Mason, E. A.
1994-06-01
A perturbation correction term for the effect of attraction forces on the equation of state is calculated and combined with previous statistical-mechanical analytical equations of state proposed by Song and Mason and by Ihm, Song, and Mason. The major effect of the correction on the p-v isotherms occurs in the metastable and unstable regions (the ``van der Waals loops''), with the result that the vapor pressures and orthobaric densities predicted from the Maxwell equal-area construction are greatly improved in accuracy. Comparison is made with experimental data for 13 selected nonpolar fluids (Ar, Kr, Xe, N2, O2, CO2, CH4, C2H6, C3H8, n-C4H10, i-C4H10, C2H4, and benzene) and one slightly polar fluid (toluene). Densities in the stable region of the p-v-T surface are accurate to about 1%-2% in the dense fluid region, and to better than 1% in the low-density gas region; the accuracy is slightly better than that achieved without the perturbation correction. Vapor pressures are predicted with an accuracy of about 2%, with orthobaric densities that are accurate to about 2% for the saturated vapor and to better than 1% for the saturated liquid. As usual for analytical equations of state, the critical region is described less accurately. In principle, the entire fluid equation of state and its vapor-liquid phase boundaries can be calculated from the intermolecular potential plus a few liquid densities. If the potential is not known, measurements of the second virial coefficient as a function of temperature can be used instead; in the absence of any such measurements, the calculation can use as input only the critical temperature, the critical pressure, and the Pitzer acentric factor, with only slight loss of accuracy. Comparison is also made with several widely used empirical equations of state. The present equation of state can be extended to include mixtures, but numerical computations on mixtures are postponed for future work.
Mushroom plasmonic metamaterial infrared absorbers
NASA Astrophysics Data System (ADS)
Ogawa, Shinpei; Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi
2015-01-01
There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF2 etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.
Additive manufacturing of RF absorbers
NASA Astrophysics Data System (ADS)
Mills, Matthew S.
The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.
Mushroom plasmonic metamaterial infrared absorbers
Ogawa, Shinpei Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi
2015-01-26
There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF{sub 2} etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.
Nonventing, Regenerable, Lightweight Heat Absorber
NASA Technical Reports Server (NTRS)
Izenson, Michael G.; Chen, Weibo
2008-01-01
A lightweight, regenerable heat absorber (RHA), developed for rejecting metabolic heat from a space suit, may also be useful on Earth for short-term cooling of heavy protective garments. Unlike prior space-suit-cooling systems, a system that includes this RHA does not vent water. The closed system contains water reservoirs, tubes through which water is circulated to absorb heat, an evaporator, and an absorber/radiator. The radiator includes a solution of LiCl contained in a porous material in titanium tubes. The evaporator cools water that circulates through a liquid-cooled garment. Water vapor produced in the evaporator enters the radiator tubes where it is absorbed into the LiCl solution, releasing heat. Much of the heat of absorption is rejected to the environment via the radiator. After use, the RHA is regenerated by heating it to a temperature of 100 C for about 2 hours to drive the absorbed water back to the evaporator. A system including a prototype of the RHA was found to be capable of maintaining a temperature of 20 C while removing heat at a rate of 200 W for 6 hours.
NASA Technical Reports Server (NTRS)
Caves, C. M.; Schumaker, B. L.
1985-01-01
A new formalism for analyzing two-photon devices, such as parametric amplifiers and phase-conjugate mirrors, is proposed in part I, focusing on the properties and the significance of the quadrature-phase amplitudes and two-mode squeezed states. Time-stationary quasi-probability noise is also detailed for the case of Gaussian noise, and uncertainty principles for the quadrature-phase amplitudes are outlined, as well as some important properties of the two-mode states. Part II establishes a mathematical foundation for the formalism, with introduction of a vector notation for compact representation of two-mode properties. Fundamental unitary operators and special quantum states are also examined with an emphasis on the two-mode squeezed states. The results are applied to a previously studied degenerate limit (epsilon = 0).
Ground-state phase diagram of a spin-orbit-coupled bosonic superfluid in an optical lattice
NASA Astrophysics Data System (ADS)
Chen, Zhu; Liang, Zhaoxin
2016-01-01
In recent experiments, spin-orbit-coupled (SOC) bosonic gases in an optical lattice have been successfully prepared into any Bloch band [Hamner et al., Phys. Rev. Lett. 114, 070401 (2015), 10.1103/PhysRevLett.114.070401], which promises a viable contender in the competitive field of simulating gauge-related phenomena. However, the ground-state phase diagram of such systems in the superfluid regime is still lacking. Here we present a detailed study of the phase diagram in an optically trapped Bose gas with equal-weight Rashba and Dresselhaus SO coupling. We identify four different quantum phases, which include three normal phases and a mixed phase, by considering the wave vector k1, the longitudinal <σz> , and the transverse <σx> spin polarizations as three order parameters. The ground state of normal phases is a Bloch wave with a single wave vector k1, which can position in arbitrary regions in the Brillouin zone. By contrast, the ground state of the mixed phase is a superposition of two Bloch waves with opposite k1, which, remarkably, may lack periodicity even though the system's Hamiltonian is periodic. This mixed phase in the lattice setting can be seen as the counterpart of the stripe phase associated with the uniform SOC gas. Furthermore, due to the lattice-renormalized SOC, the phase diagram of the model system becomes significantly different from the uniform case when the lattice strength grows. Finally, a scheme for experimentally probing the mixed phase using Bragg spectroscopy is proposed.