Eesti Teadusfondi preemia Astrid Haljasele ja Tõnu Laasile

Index Scriptorium Estoniae

2000-01-01

Eesti Teadusfondi täppisteaduste ekspertkomisjoni poolt korraldatud magistrantide ja doktorantide teadustööde konkursil määrati preemia 4000 krooni loodusteaduste osakonna teadurile Astrid Haljasele artikli Mankin, R., Ainsaar, A., Haljas, A. Trichotomous-noise-induced phase transitions for the stochastic Hongler model. Proc. Estonian Acad. Sci. Phys. Math., 2000, 49, 1, 28-39 eest. Loodusteaduste osakonna assistendile, TPÜ doktorandile Tõnu Laasile määrati preemia 7000 krooni artiklite sarja Lainete levik kõveras aeg-ruumis eest : [täistekst

Pressure induced phase transition behaviour in -electron based ...

Indian Academy of Sciences (India)

The present review on the high pressure phase transition behaviour of ... For instance, closing of energy gaps lead to metal–insulator transitions [4], shift in energy ... systematic study of the pressure induced structural sequences has become ...

Lightning-Discharge Initiation as a Noise-Induced Kinetic Transition

Science.gov (United States)

Iudin, D. I.

2017-10-01

The electric fields observed in thunderclouds have the peak values one order of magnitude smaller than the electric strength of air. This fact renders the issue of the lightning-discharge initiation one of the most intriguing problems of thunderstorm electricity. In this work, the lightning initiation in a thundercloud is considered as a noise-induced kinetic transition. The stochastic electric field of the charged hydrometeors is the noise source. The considered kinetic transition has some features which distinguish it from other lightning-initiation mechanisms. First, the dynamic realization of this transition, which is due to interaction of the electron and ion components, is extended for a time significantly exceeding the spark-discharge development time. In this case, the fast attachment of electrons generated by supercritical bursts of the electric field of hydrometeors is balanced during long-term time intervals by the electron-release processes when the negative ions are destroyed. Second, an important role in the transition kinetics is played by the stochastic drift of electrons and ions caused by the small-scale fluctuations of the field of charged hydrometeors. From the formal mathematical viewpoint, this stochastic drift is indistinguishable from the scalar-impurity advection in a turbulent flow. In this work, it is shown that the efficiency of "advective mixing" is several orders of magnitude greater than that of the ordinary diffusion. Third, the considered transition leads to a sharp increase in the conductivity in the exponentially rare compact regions of space against the background of the vanishingly small variations in the average conductivity of the medium. In turn, the spots with increased conductivity are polarized in the mean field followed by the streamer initiation and discharge contraction.

Characterization and reduction of noise in Mo/Au transition edge sensors

International Nuclear Information System (INIS)

Lindeman, Mark A.; Bandler, Simon; Brekosky, Regis P.; Chervenak, James A.; Figueroa-Feliciano, Enectali; Finkbeiner, Fred M.; Saab, Tarek; Stahle, Caroline K.

2004-01-01

We measured noise in a variety of Mo/Au transition-edge sensor (TES) X-ray calorimeters. We investigated the relationship between the noise, bias, and the superconducting phase transition in the TESs. Our square TES calorimeters have achieved very good energy resolutions (2.4 eV at 1.5 keV) but their resolutions have been limited by broadband white excess noise generated by the TES when it is biased in the phase transition. We have recently fabricated Mo/Cu TESs with interdigitated normal metal bars deposited on top of the bilayer. The new TES calorimeters have demonstrated little or no excess noise in the phase transition. These results point the way to development of TES calorimeters with higher energy resolution

Analytical expressions for transition edge sensor excess noise models

International Nuclear Information System (INIS)

Brandt, Daniel; Fraser, George W.

2010-01-01

Transition edge sensors (TESs) are high-sensitivity thermometers used in cryogenic microcalorimeters which exploit the steep gradient in resistivity with temperature during the superconducting phase transition. Practical TES devices tend to exhibit a white noise of uncertain origin, arising inside the device. We discuss two candidate models for this excess noise, phase slip shot noise (PSSN) and percolation noise. We extend the existing PSSN model to include a magnetic field dependence and derive a basic analytical model for percolation noise. We compare the predicted functional forms of the noise current vs. resistivity curves of both models with experimental data and provide a set of equations for both models to facilitate future experimental efforts to clearly identify the source of excess noise.

Phase noise of dispersion-managed solitons

International Nuclear Information System (INIS)

Spiller, Elaine T.; Biondini, Gino

2009-01-01

We quantify noise-induced phase deviations of dispersion-managed solitons (DMS) in optical fiber communications and femtosecond lasers. We first develop a perturbation theory for the dispersion-managed nonlinear Schroedinger equation (DMNLSE) in order to compute the noise-induced mean and variance of the soliton parameters. We then use the analytical results to guide importance-sampled Monte Carlo simulations of the noise-driven DMNLSE. Comparison of these results with those from the original unaveraged governing equations confirms the validity of the DMNLSE as a model for many dispersion-managed systems and quantify the increased robustness of DMS with respect to noise-induced phase jitter.

Novel BCH Code Design for Mitigation of Phase Noise Induced Cycle Slips in DQPSK Systems

DEFF Research Database (Denmark)

Leong, M. Y.; Larsen, Knud J.; Jacobsen, G.

2014-01-01

We show that by proper code design, phase noise induced cycle slips causing an error floor can be mitigated for 28 Gbau d DQPSK systems. Performance of BCH codes are investigated in terms of required overhead......We show that by proper code design, phase noise induced cycle slips causing an error floor can be mitigated for 28 Gbau d DQPSK systems. Performance of BCH codes are investigated in terms of required overhead...

The novel phenomenon of noise-catalyzed chaos-order transitions

Energy Technology Data Exchange (ETDEWEB)

Gassmann, F. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Numerical simulations of the Lorenzian water wheel have been used to investigate the influence of stochastic noise on the lifetime of chaotic transients. Whereas in one region of parameter space no noise dependency could be detected, a shortening of the lifetimes by more than four decades was found in another region. This large effect was produced by a significant modification of the attraction basin of a quasistable stationary state rather than by affecting the chaotic orbits before the chaos-order transition occurred. This novel phenomenon of noise-induced chaos-order transitions is not related to stochastic resonance or other noise-induced effects. (author) 2 figs., 5 refs.

Noise-induced transitions at a Hopf bifurcation in a first-order delay-differential equation

International Nuclear Information System (INIS)

Longtin, A.

1991-01-01

The influence of colored noise on the Hopf bifurcation in a first-order delay-differential equation (DDE), a model paradigm for nonlinear delayed feedback systems, is considered. First, it is shown, using a stability analysis, how the properties of the DDE depend on the ratio R of system delay to response time. When this ratio is small, the DDE behaves more like a low-dimensional system of ordinary differential equations (ODE's); when R is large, one obtains a singular perturbation limit in which the behavior of the DDE approaches that of a discrete time map. The relative magnitude of the additive and multiplicative noise-induced postponements of the Hopf bifurcation are numerically shown to depend on the ratio R. Although both types of postponements are minute in the large-R limit, they are almost equal due to an equivalence of additive and parametric noise for discrete time maps. When R is small, the multiplicative shift is larger than the additive one at large correlation times, but the shifts are equal for small correlation times. In fact, at constant noise power, the postponement is only slightly affected by the correlation time of the noise, except when the noise becomes white, in which case the postponement drastically decreases. This is a numerical study of the stochastic Hopf bifurcation, in ODE's or DDE's, that looks at the effect of noise correlation time at constant power. Further, it is found that the slope at the fixed point averaged over the stochastic-parameter motion acts, under certain conditions, as a quantitative indicator of oscillation onset in the presence of noise. The problem of how properties of the DDE carry over to ODE's and to maps is discussed, along with the proper theoretical framework in which to study nonequilibrium phase transitions in this class of functional differential equations

Stochastic kinetics of photoinduced phase transitions in spin-crossover solids

Science.gov (United States)

Gudyma, Iurii; Maksymov, Artur; Dimian, Mihai

2013-10-01

We study the stochastic macroscopic kinetics of photoinduced phase transitions in spin-crossover compounds assisted by white and colored Ornstein-Uhlenbeck noise. By using a phenomenological master equation obtained in the mean-field approach, the phase diagram is constructed based on the associated Lyapunov function. The stochastic behavior is then analyzed in the Langevin framework and the corresponding Fokker-Planck equations. Both additive and multiplicative and white and colored types of noise are considered and the stationary probability densities are found along with the noise-assisted light induced hysteretic loops. By using the Kramers formalism, we also focus our attention on the escape time problem in these noise perturbed systems. A detailed study of the relative escape time dependence on various noise characteristics is performed and the main features are compared for different types of noise.

Fermionic phase transition induced by the effective impurity in holography

Energy Technology Data Exchange (ETDEWEB)

Fang, Li-Qing [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); School of Physics and Electronic Information, Shangrao Normal University,Shangrao 334000 (China); Kuang, Xiao-Mei [Department of Physics, National Technical University of Athens,GR-15780 Athens (Greece); Instituto de Física, Pontificia Universidad Católica de Valparaíso,Casilla 4059, Valparaíso (Chile); Wang, Bin [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); Wu, Jian-Pin [Institute of Gravitation and Cosmology, Department of Physics,School of Mathematics and Physics, Bohai University, Jinzhou 121013 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences, Beijing 100190 (China)

2015-11-20

We investigate the holographic fermionic phase transition induced by the effective impurity in holography, which is introduced by massless scalar fields in Einstein-Maxwell-massless scalar gravity. We obtain a phase diagram in (α,T) plane separating the Fermi liquid phase and the non-Fermi liquid phase.

Validity and Reliability of Trichotomous Achievement Goal Scale

Science.gov (United States)

Ilker, Gokce Erturan; Arslan, Yunus; Demirhan, Giyasettin

2011-01-01

The Trichotomous Achievement Goal Scale was developed by Agbuga and Xiang (2008) by including selected items from the scales of Duda and Nicholls (1992), Elliot (1999), and Elliot and Church (1997) and adapting them into Turkish. The scale consists of 18 items, and students rated each item on a 7-point Likert scale. To ascertain the validity and…

Hydrostatic-pressure induced phase transition of phonons in single-walled nanotubes

International Nuclear Information System (INIS)

Feng Peng; Meng Qingchao

2009-01-01

We study the effect of the hydrostatic pressure on the phonons in single-walled carbon nanotubes (SWNTs) in a magnetic field. We calculate the magnetic moments of the phonons using a functional integral technique, and find that the phonons in SWNTs undergo a pressure-induced phase transition from the paramagnetic phase to the diamagnetic phase under hydrostatic pressure 2 GPa. We explain the mechanism of generating this phase transition.

Pressure-induced phase transitions in nanocrystalline ReO3

International Nuclear Information System (INIS)

Biswas, Kanishka; Muthu, D V S; Sood, A K; Kruger, M B; Chen, B; Rao, C N R

2007-01-01

Pressure-induced phase transitions in the nanocrystals of ReO 3 with an average diameter of ∼12 nm have been investigated in detail by using synchrotron x-ray diffraction and the results compared with the literature data of bulk samples of ReO 3 . The study shows that the ambient-pressure cubic I phase (space group Pm3-barm) transforms to a monoclinic phase (space group C 2/c), then to a rhombohedral I phase (space group R3-barc), and finally to another rhombohedral phase (rhombohedral II, space group R3-barc) with increasing pressure over the 0.0-20.3 GPa range. The cubic I to monoclinic transition is associated with the largest volume change (∼5%), indicative of a reconstructive transition. The transition pressures are generally lower than those known for bulk ReO 3 . The cubic II (Im3-bar) or tetragonal (P4/mbm) phases do not occur at lower pressures. The nanocrystals are found to be more compressible than bulk ReO 3 . On decompression to ambient pressure, the structure does not revert back to the cubic I structure

Effect of Parametric Dichotomic Markov Noise on the Properties of Chaotic Transitions in Dynamical Systems

Science.gov (United States)

Gac, J. M.; Żebrowski, J. J.

A chaotic transition occurs when a continuous change of one of the parameters of the system causes a discontinuous change in the properties of the chaotic attractor of the system. Such phenomena are present in many dynamical systems, in which a chaotic behavior occurs. The best known of these transitions are: the period-doubling bifurcation cascade, intermittency and crises. The effect of dichotomous Markov noise (DMN) on the properties of systems with chaotic transitions is discussed. DMN is a very simple two-valued stochastic process, with constant transition rates between the two states. In spite of its simplicity, this kind of noise is a very powerful tool to describe various phenomena present in many physical, chemical or biological systems. Many interesting phenomena induced by DMN are known. However, there is no research on the effect of this kind of noise on intermittency or crises. We present the change of the mean laminar phase length and of laminar phase length distribution caused by DMN modulating the parameters of a system with intermittency and the modification of the mean life time on the pre-crisis attractor in the case of a boundary crisis. The results obtained analytically are compared with numerical simulations for several simple dynamical systems.

Noise-induced phase space transport in two-dimensional Hamiltonian systems.

Science.gov (United States)

Pogorelov, I V; Kandrup, H E

1999-08-01

First passage time experiments were used to explore the effects of low amplitude noise as a source of accelerated phase space diffusion in two-dimensional Hamiltonian systems, and these effects were then compared with the effects of periodic driving. The objective was to quantify and understand the manner in which "sticky" chaotic orbits that, in the absence of perturbations, are confined near regular islands for very long times, can become "unstuck" much more quickly when subjected to even very weak perturbations. For both noise and periodic driving, the typical escape time scales logarithmically with the amplitude of the perturbation. For white noise, the details seem unimportant: Additive and multiplicative noise typically have very similar effects, and the presence or absence of a friction related to the noise by a fluctuation-dissipation theorem is also largely irrelevant. Allowing for colored noise can significantly decrease the efficacy of the perturbation, but only when the autocorrelation time, which vanishes for white noise, becomes so large that there is little power at frequencies comparable to the natural frequencies of the unperturbed orbit. Similarly, periodic driving is relatively inefficient when the driving frequency is not comparable to these natural frequencies. This suggests that noise-induced extrinsic diffusion, like modulational diffusion associated with periodic driving, is a resonance phenomenon. The logarithmic dependence of the escape time on amplitude reflects the fact that the time required for perturbed and unperturbed orbits to diverge a given distance scales logarithmically in the amplitude of the perturbation.

Invasion-wave-induced first-order phase transition in systems of active particles.

Science.gov (United States)

Ihle, Thomas

2013-10-01

An instability near the transition to collective motion of self-propelled particles is studied numerically by Enskog-like kinetic theory. While hydrodynamics breaks down, the kinetic approach leads to steep solitonlike waves. These supersonic waves show hysteresis and lead to an abrupt jump of the global order parameter if the noise level is changed. Thus they provide a mean-field mechanism to change the second-order character of the phase transition to first order. The shape of the wave is shown to follow a scaling law and to quantitatively agree with agent-based simulations.

Noise-induced phase space transport in two-dimensional Hamiltonian systems

International Nuclear Information System (INIS)

Pogorelov, I.V.; Kandrup, H.E.

1999-01-01

First passage time experiments were used to explore the effects of low amplitude noise as a source of accelerated phase space diffusion in two-dimensional Hamiltonian systems, and these effects were then compared with the effects of periodic driving. The objective was to quantify and understand the manner in which open-quotes stickyclose quotes chaotic orbits that, in the absence of perturbations, are confined near regular islands for very long times, can become open-quotes unstuckclose quotes much more quickly when subjected to even very weak perturbations. For both noise and periodic driving, the typical escape time scales logarithmically with the amplitude of the perturbation. For white noise, the details seem unimportant: Additive and multiplicative noise typically have very similar effects, and the presence or absence of a friction related to the noise by a fluctuation-dissipation theorem is also largely irrelevant. Allowing for colored noise can significantly decrease the efficacy of the perturbation, but only when the autocorrelation time, which vanishes for white noise, becomes so large that there is little power at frequencies comparable to the natural frequencies of the unperturbed orbit. Similarly, periodic driving is relatively inefficient when the driving frequency is not comparable to these natural frequencies. This suggests that noise-induced extrinsic diffusion, like modulational diffusion associated with periodic driving, is a resonance phenomenon. The logarithmic dependence of the escape time on amplitude reflects the fact that the time required for perturbed and unperturbed orbits to diverge a given distance scales logarithmically in the amplitude of the perturbation. copyright 1999 The American Physical Society

Ultrafast Hot Electron Induced Phase Transitions in Vanadium Dioxide

Directory of Open Access Journals (Sweden)

Haglund R. F.

2013-03-01

Full Text Available The Au/Cr/VO2/Si system was investigated in pump–probe experiments. Hot-electrons generated in the Au were found to penetrate into the underlying VO2 and couple with its lattice inducing a semiconductor-to-metal phase transition in ~2 picoseconds.

Study on phase noise induced by 1/f noise of the modulator drive circuit in high-sensitivity fiber optic gyroscope

Science.gov (United States)

Teng, Fei; Jin, Jing; Li, Yong; Zhang, Chunxi

2018-05-01

The contribution of modulator drive circuit noise as a 1/f noise source to the output noise of the high-sensitivity interferometric fiber optic gyroscope (IFOG) was studied here. A noise model of closed-loop IFOG was built. By applying the simulated 1/f noise sequence into the model, a gyroscope output data series was acquired, and the corresponding power spectrum density (PSD) and the Allan variance curve were calculated to analyze the noise characteristic. The PSD curve was in the spectral shape of 1/f, which verifies that the modulator drive circuit induced a low frequency 1/f phase noise into the gyroscope. The random walk coefficient (RWC), a standard metric to characterize the noise performance of the IFOG, was calculated according to the Allan variance curve. Using an operational amplifier with an input 1/f noise of 520 nV/√Hz at 1 Hz, the RWC induced by this 1/f noise was 2 × 10-4°/√h, which accounts for 63% of the total RWC. To verify the correctness of the noise model we proposed, a high-sensitivity gyroscope prototype was built and tested. The simulated Allan variance curve gave a good rendition of the prototype actual measured curve. The error percentage between the simulated RWC and the measured value was less than 13%. According to the model, a noise reduction method is proposed and the effectiveness is verified by the experiment.

Dipolar-induced interplay between inter-level physics and macroscopic phase transitions in triple-well potentials

International Nuclear Information System (INIS)

Zhang Aixia; Xue Jukui

2012-01-01

We propose a scheme to reveal the interplay between dipole–dipole interaction (DDI), inter-level coupling and macroscopic phase transitions in dipolar condensates. By considering a macroscopic sample of dipolar bosons in triple-well potentials, DDI-induced coupling between the inter-level physics and the macroscopic phase transitions is presented. When the DDI exceeds certain thresholds, the degeneracy of the two lowest energy levels and the excitation of new eigenstates occur, respectively. Interestingly, these thresholds give the boundaries of various quantum phase transitions. That is, the quantum phase transitions are the consequence of the levels' degeneracy and the new eigenstates' excitation. Furthermore, DDI-induced long-range macroscopic Josephson oscillations are observed and long-range coherent quantum transportation is achieved. Our results give clear proof of the interplay between the multi-level physics and quantum phase transitions, and also provide a way for designing the long-range coherent quantum transportation. (paper)

Noise-Induced Transition in a Voltage-Controlled Oscillator Neuron Model

International Nuclear Information System (INIS)

Xie Huizhang; Liu Xuemei; Li Zhibing; Ai Baoquan; Liu Lianggang

2008-01-01

In the presence of Gaussian white noise, we study the properties of voltage-controlled oscillator neuron model and discuss the effects of the additive and multiplicative noise. It is found that the additive noise can accelerate and counterwork the firing of neuron, which depends on the value of central frequency of neuron itself, while multiplicative noise can induce the continuous change or mutation of membrane potential

Ultrafast studies of shock-induced melting and phase transitions at LCLS

Science.gov (United States)

McMahon, Malcolm

The study of shock-induced phase transitions, which is vital to the understanding of material response to rapid pressure changes, dates back to the 1950s, when Bankcroft et al reported a transition in iron. Since then, many transitions have been reported in a wide range of materials, but, due to the lack of sufficiently bright x-ray sources, the structural details of these new phases has been notably lacking. While the development of nanosecond in situ x-ray diffraction has meant that lattice-level studies of such phenomena have become possible, including studies of the phase transition reported 60 years ago in iron, the quality of the diffraction data from such studies is noticeably poorer than that obtained from statically-compressed samples on synchrotrons. The advent of x-ray free electron lasers (XFELs), such as the LCLS, has resulted in an unprecedented improvement in the quality of diffraction data that can be obtained from shock-compressed matter. Here I describe the results from three recent experiment at the LCLS that looked at the solid-solid and solid-liquid phase transitions in Sb, Bi and Sc using single 50 fs x-ray exposures. The results provide new insight into the structural changes and melting induced by shock compression. This work is supported by EPSRC under Grant No. EP/J017051/1. Use of the LCLS, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.

Pressure-induced phase transitions of multiferroic BiFeO3

OpenAIRE

XiaoLi, Zhang; Ye, Wu; Qian, Zhang; JunCai, Dong; Xiang, Wu; Jing, Liu; ZiYu, Wu; DongLiang, Chen

2013-01-01

Pressure-induced phase transitions of multiferroic BiFeO3 have been investigated using synchrotron radiation X-ray diffraction with diamond anvil cell technique at room temperature. Present experimental data clearly show that rhombohedral (R3c) phase of BiFeO3 first transforms to monoclinic (C2/m) phase at 7 GPa, then to orthorhombic (Pnma) phase at 11 GPa, which is consistent with recent theoretical ab initio calculation. However, we observe another peak at 2{\\theta}=7{\\deg} in the pressure ...

Photo-induced phase transition: from where it comes and to where it goes?

International Nuclear Information System (INIS)

Koshihara, Shin-ya

2005-01-01

It is an attractive target for materials science to find a system which shows the phase transition triggered by external stimulation of light. The purpose of our study is to review experimental evidences indicating that the photo-injected local excitation can really trigger the cooperative phenomena in solids. In this sense, this unique photo-induced effect can be named as photo-induced phase transition (PIPT). Here, I will also make brief review on the experimental research on PIPT combining with a development of ultra-fast quantum electronics technology

Photo-induced charge-transfer phase transition of rubidium manganese hexacyanoferrate in ferromagnetic and paramagnetic states

International Nuclear Information System (INIS)

Tokoro, Hiroko; Hashimoto, Kazuhito; Ohkoshi, Shin-ichi

2007-01-01

A charge transfer phase transition with thermal hysteresis loop is observed in a series of rubidium manganese hexacyanoferrates, RbMn[Fe(China) 6 ] (1), Rb 0.88 Mn[Fe(China) 6 ] 0.96 .0.6H 2 O (2), and Rb 0.97 Mn[Fe(China) 6 ] 0.99 .0.2H 2 O (3). This phase transition is accompanied by a structural change from cubic (F4-bar 3m) to tetragonal (I4-bar m2). Its high-temperature (HT) and low-temperature (LT) phases are composed of Mn II (S=2/5)NC-Fe III (S=1/2) and Mn III (S=2)-NC-Fe II (S=0), respectively. The phase transition is caused by a metal-to-metal charge transfer from Mn II to Fe III and a Jahn-Teller distortion of the produced Mn III ion. At the ferromagnetic state in LT phase of 2, the photo-induced phase transition is observed, i.e., magnetization is quenched by the irradiation with only one shot of laser pulse. This phenomenon is caused by a photo-induced phase transition from the LT phase to the HT phase. In 3, optical switching between LT and HT phases at room temperature in paramagnetic region is observed

Magnetic phase transition induced by electrostatic gating in two-dimensional square metal-organic frameworks

Science.gov (United States)

Wang, Yun-Peng; Li, Xiang-Guo; Liu, Shuang-Long; Fry, James N.; Cheng, Hai-Ping

2018-03-01

We investigate theoretically magnetism and magnetic phase transitions induced by electrostatic gating of two-dimensional square metal-organic framework compounds. We find that electrostatic gating can induce phase transitions between homogeneous ferromagnetic and various spin-textured antiferromagnetic states. Electronic structure and Wannier function analysis can reveal hybridizations between transition-metal d orbitals and conjugated π orbitals in the organic framework. Mn-containing compounds exhibit a strong d -π hybridization that leads to partially occupied spin-minority bands, in contrast to compounds containing transition-metal ions other than Mn, for which electronic structure around the Fermi energy is only slightly spin split due to weak d -π hybridization and the magnetic interaction is of the Ruderman-Kittel-Kasuya-Yosida type. We use a ferromagnetic Kondo lattice model to understand the phase transition in Mn-containing compounds in terms of carrier density and illuminate the complexity and the potential to control two-dimensional magnetization.

Pressure induced structural phase transition of OsB2: First-principles calculations

International Nuclear Information System (INIS)

Ren Fengzhu; Wang Yuanxu; Lo, V.C.

2010-01-01

Orthorhombic OsB 2 was synthesized at 1000 deg. C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB 2 . An analysis of the calculated enthalpy shows that orthorhombic OsB 2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 6 3 /mmc structure (high-pressure phase) is stable for OsB 2 . We expect the phase transition can be further confirmed by the experimental work. - Abstract: Graphical Abstract Legend (TOC Figure): Table of Contents Figure Pressure induced structural phase transition from the orthorhombic structure to the hexagonal one for OsB 2 takes place under 10.8 GPa (0 K), 10.35 GPa (300, 1000 K) by the first-principles predictions.

Electric field-induced phase transitions in Li-modified Na{sub 0.5}K{sub 0.5}NbO{sub 3} at the polymorphic phase boundary

Energy Technology Data Exchange (ETDEWEB)

Iamsasri, Thanakorn; Jones, Jacob L., E-mail: jacobjones@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Tutuncu, Goknur [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Uthaisar, Chunmanus; Pojprapai, Soodkhet [School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakorn Ratchasima 30000 (Thailand); Wongsaenmai, Supattra [Program in Materials Science, Faculty of Science, Maejo University, Chiang Mai 50290 (Thailand)

2015-01-14

The electric field-induced phase transitions in Li-modified Na{sub 0.5}K{sub 0.5}NbO{sub 3} at the polymorphic phase boundary (PPB) were observed using in situ X-ray diffraction. The ratio of monoclinic to tetragonal phase fraction was used as an indicator of the extent and reversibility of the phase transitions. The reversibility of the phase transition was greater in compositions further from the PPB. These results demonstrate that the field-induced phase transition is one of the origins of high piezoelectric properties in lead-free ferroelectric materials.

Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4

Directory of Open Access Journals (Sweden)

Simone Techert

2009-09-01

Full Text Available Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse/x-ray probe (pulse techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated.

Pressure-induced phase transition of 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6

Science.gov (United States)

Takekiyo, Takahiro; Hatano, Naohiro; Imai, Yusuke; Abe, Hiroshi; Yoshimura, Yukihiro

2011-03-01

We have investigated the pressure-induced Raman spectral change of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) using Raman spectroscopy. The relative Raman intensity at 590 cm-1 of the CH2 rocking band assigned to the gauche conformer of the NCCC dihedral angle of the butyl group in the [bmim]+ cation increases when the pressure-induced liquid-crystalline phase transition occurs, while that at 610 cm-1 assigned to the trans conformer decreases. Our results show that the high-pressure phase transition of [bmim][PF6] causes the increase of the gauche conformer of the [bmim]+ cation.

Phase transitions in the q -voter model with noise on a duplex clique

Science.gov (United States)

Chmiel, Anna; Sznajd-Weron, Katarzyna

2015-11-01

We study a nonlinear q -voter model with stochastic noise, interpreted in the social context as independence, on a duplex network. To study the role of the multilevelness in this model we propose three methods of transferring the model from a mono- to a multiplex network. They take into account two criteria: one related to the status of independence (LOCAL vs GLOBAL) and one related to peer pressure (AND vs OR). In order to examine the influence of the presence of more than one level in the social network, we perform simulations on a particularly simple multiplex: a duplex clique, which consists of two fully overlapped complete graphs (cliques). Solving numerically the rate equation and simultaneously conducting Monte Carlo simulations, we provide evidence that even a simple rearrangement into a duplex topology may lead to significant changes in the observed behavior. However, qualitative changes in the phase transitions can be observed for only one of the considered rules: LOCAL&AND. For this rule the phase transition becomes discontinuous for q =5 , whereas for a monoplex such behavior is observed for q =6 . Interestingly, only this rule admits construction of realistic variants of the model, in line with recent social experiments.

Pressure-induced phase transitions in acentric BaHf(BO{sub 3}){sub 2}

Energy Technology Data Exchange (ETDEWEB)

Mączka, Mirosław, E-mail: m.maczka@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Szymborska-Małek, Katarzyna [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Sousa Pinheiro, Gardenia de [Departamento de Física, Universidade Federal do Piauí, Teresina, PI 64049-550 (Brazil); Cavalcante Freire, Paulo Tarso [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza CE-60455-970 (Brazil); Majchrowski, Andrzej [Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Street, 00-908 Warszawa (Poland)

2015-08-15

High-pressure Raman scattering studies revealed that BaHf(BO{sub 3}){sub 2} is more compressible than calcite-type orthoborates and calcite, aragonite or dolomite carbonates. It undergoes a first-order reversible pressure-induced phase transition in the 3.9–4.4 GPa pressure range. Second structural change is observed at 9.2 GPa. The intermediate phase is most likely trigonal. However, Raman results suggest increase in the number of distinct BO{sub 3} groups from two in the ambient pressure phase to at least three in the intermediate phase. This intermediate phase is also strongly compressible and strong pressure dependence of the lattice modes proves that the main changes under pressure occur within the layers built from BaO{sub 6} and HfO{sub 6} octahedra. The second phase transition leads most likely to lowering of the trigonal symmetry, as evidenced by significant increase of the number of observed bands. The pressure coefficients of the Raman bands of the high-pressure phase are relatively small, suggesting more dense arrangement of the metal–oxygen polyhedra and BO{sub 3} groups in this phase. It is worth noting that the high-pressure phase was not reached in the second compression experiment up to 10 GPa. This behavior can be most likely attributed to worse hydrostatic conditions of the first experiment. - Graphical abstract: Raman spectra of BaHf(BO{sub 3}){sub 2} recorded at different pressures during compression showing onset of pressure-induced phase transitions. - Highlights: • High-pressure Raman spectra were measured for BaHf(BO{sub 3}){sub 2.} • BaHf(BO{sub 3}){sub 2} undergoes a reversible first-order phase transition at 3.9–4.4 GPa into a trigonal phase. • The intermediate trigonal phase is strongly compressible second structural transformation is observed at 9.2 GPa under non-perfect hydrostatic conditions.

Ab initio molecular dynamics study of pressure-induced phase transition in ZnS

International Nuclear Information System (INIS)

Martinez, Israel; Durandurdu, Murat

2006-01-01

The pressure-induced phase transition in zinc sulfide is studied using a constant-pressure ab initio technique. The reversible phase transition from the zinc-blende structure to a rock-salt structure is successfully reproduced through the simulations. The transformation mechanism at the atomistic level is characterized and found to be due to a monoclinic modification of the simulation cell, similar to that obtained in SiC. This observation supports the universal transition state of high-pressure zinc-blende to rock-salt transition in semiconductor compounds. We also study the role of stress deviations on the transformation mechanism and find that the system follows the same transition pathway under nonhydrostatic compressions as well

Pressure-induced phase transitions of multiferroic BiFeO3

International Nuclear Information System (INIS)

Zhang Xiaoli; Dong Juncai; Liu Jing; Chen Dongliang; Wu Ye; Zhang Qian; Wu Xiang; Wu Ziyu

2013-01-01

Pressure-induced phase transitions of multiferroic BiFeO 3 have been investigated using synchrotron radiation X-ray diffraction with diamond anvil cell technique at room temperature. Present experimental data clearly show that rhombohedral (R3c) phase of BiFeO 3 first transforms to monoclinic (C2/m) phase at 7 GPa, then to orthorhombic (Pnma) phase at 11 GPa, which is consistent with recent theoretical ab initio calculation. However, we observe another peak at 2θ=7° in the pressure range of 5-7 GPa that has not been reported previously. Further analysis reveals that this reflection peak is attributed to the orthorhombic (Pbam) phase, indicating the coexistence of monoclinic phase with orthorhombic phase in low pressure range. (authors)

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

Science.gov (United States)

Rehn, Daniel A.; Li, Yao; Pop, Eric; Reed, Evan J.

2018-01-01

Structural phase-change materials are of great importance for applications in information storage devices. Thermally driven structural phase transitions are employed in phase-change memory to achieve lower programming voltages and potentially lower energy consumption than mainstream nonvolatile memory technologies. However, the waste heat generated by such thermal mechanisms is often not optimized, and could present a limiting factor to widespread use. The potential for electrostatically driven structural phase transitions has recently been predicted and subsequently reported in some two-dimensional materials, providing an athermal mechanism to dynamically control properties of these materials in a nonvolatile fashion while achieving potentially lower energy consumption. In this work, we employ DFT-based calculations to make theoretical comparisons of the energy required to drive electrostatically-induced and thermally-induced phase transitions. Determining theoretical limits in monolayer MoTe2 and thin films of Ge2Sb2Te5, we find that the energy consumption per unit volume of the electrostatically driven phase transition in monolayer MoTe2 at room temperature is 9% of the adiabatic lower limit of the thermally driven phase transition in Ge2Sb2Te5. Furthermore, experimentally reported phase change energy consumption of Ge2Sb2Te5 is 100-10,000 times larger than the adiabatic lower limit due to waste heat flow out of the material, leaving the possibility for energy consumption in monolayer MoTe2-based devices to be orders of magnitude smaller than Ge2Sb2Te5-based devices.

Laser-induced microscopic phase-transition on an ionic liquid

International Nuclear Information System (INIS)

Iguchi, Natsuki; Datta, Alokmay; Yoshikawa, Kenichi; Ma Yue

2009-01-01

Nematic-isotropic transition is induced in a 5 μm 'droplet' within an oriented bulk of a mixture of a liquid crystalline material with a room-temperature ionic liquid, by a laser working at 532 nm with an output power of 200 mW and a beam diameter of 1 μm. No microscopic phase transition is observed either in absence of the ionic liquid or at the other wavelength of 1064 nm, available to the Nd-YAG laser. This indicates the essential role on a resonant transfer of energy to the ionic liquid from the laser radiation, which is subsequently transferred to the liquid crystal. Spectroscopy of the pure liquid crystal and ionic liquid samples confirms this concept. Spatio-temporal image of the droplet growth shows, however, that the phase transition remains confined within the microscopic domain for the first 50 s, and then spreads out rapidly. Since resonant, quantum transitions between molecular levels takes place in less than microseconds, the about seven orders of magnitude slowing down of energy transfer observed here suggests unique hierarchical dynamics including the coupling between the intra-molecular motions in the ionic liquid and the inter-molecular forces between ionic liquid and liquid crystal.

Contribution to the investigation of phase transitions induced by irradiation in insulating crystalline ceramics

International Nuclear Information System (INIS)

Simeone, D.

2003-01-01

The author gives a rather detailed overview of his research activities on the behaviour of ceramics subjected to irradiations by charged or not-charged particles. He reports the development of a new application of low incidence X ray diffraction to assess the evolutions within irradiated solids. Coupling this technique with Raman spectroscopy studies enabled the monitoring of order parameter evolution in these solids. He shows that, in some oxides, irradiation effects entail order-disorder type transitions and, more surprisingly, displacive phase transitions. From this experimental work, he developed a modelling of these phase transitions induced by irradiation. Quantitative data obtained on the evolutions of order parameters enabled these phase transitions to be explained within the frame of the thermodynamics of off-equilibrium phenomena

Light-induced ultrafast phase transitions in VO2 thin film

International Nuclear Information System (INIS)

Lysenko, S.; Rua, A.J.; Vikhnin, V.; Jimenez, J.; Fernandez, F.; Liu, H.

2006-01-01

Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 deg. C. As a kind of functional material, VO 2 thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO 2 were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm 2 . The observed PT is associated with the optical interband transition in VO 2 thin film. It suggests that with a pump laser illuminating on the film, excitation from the d θ,ε - state of valence band to the unoccupied excited mixed d θ,ε -π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d θ,ε -π* - state of the metallic phase band

Gravitationally self-induced phase transition

International Nuclear Information System (INIS)

Novello, M.; Duque, S.L.S.

1990-01-01

We propose a new mechanism by means of which a phase transition can be stimulated by self-gravitating matter. We suggest that this model could be used to explain the observed isotropy of the Universe. (orig.)

Trichotomous Processes in Early Memory Development, Aging, and Neurocognitive Impairment: A Unified Theory

Science.gov (United States)

Brainerd, C. J.; Reyna, V. F.; Howe, M. L.

2009-01-01

One of the most extensively investigated topics in the adult memory literature, dual memory processes, has had virtually no impact on the study of early memory development. The authors remove the key obstacles to such research by formulating a trichotomous theory of recall that combines the traditional dual processes of recollection and…

Noise-induced polarization switching in complex networks

Science.gov (United States)

Haerter, Jan O.; Díaz-Guilera, Albert; Serrano, M. Ángeles

2017-04-01

The combination of bistability and noise is ubiquitous in complex systems, from biology to social interactions, and has important implications for their functioning and resilience. Here we use a simple three-state dynamical process, in which nodes go from one pole to another through an intermediate state, to show that noise can induce polarization switching in bistable systems if dynamical correlations are significant. In large, fully connected networks, where dynamical correlations can be neglected, increasing noise yields a collapse of bistability to an unpolarized configuration where the three possible states of the nodes are equally likely. In contrast, increased noise induces abrupt and irreversible polarization switching in sparsely connected networks. In multiplexes, where each layer can have a different polarization tendency, one layer is dominant and progressively imposes its polarization state on the other, offsetting or promoting the ability of noise to switch its polarization. Overall, we show that the interplay of noise and dynamical correlations can yield discontinuous transitions between extremes, which cannot be explained by a simple mean-field description.

Complex Nonlinearity Chaos, Phase Transitions, Topology Change and Path Integrals

CERN Document Server

Ivancevic, Vladimir G

2008-01-01

Complex Nonlinearity: Chaos, Phase Transitions, Topology Change and Path Integrals is a book about prediction & control of general nonlinear and chaotic dynamics of high-dimensional complex systems of various physical and non-physical nature and their underpinning geometro-topological change. The book starts with a textbook-like expose on nonlinear dynamics, attractors and chaos, both temporal and spatio-temporal, including modern techniques of chaos–control. Chapter 2 turns to the edge of chaos, in the form of phase transitions (equilibrium and non-equilibrium, oscillatory, fractal and noise-induced), as well as the related field of synergetics. While the natural stage for linear dynamics comprises of flat, Euclidean geometry (with the corresponding calculation tools from linear algebra and analysis), the natural stage for nonlinear dynamics is curved, Riemannian geometry (with the corresponding tools from nonlinear, tensor algebra and analysis). The extreme nonlinearity – chaos – corresponds to th...

Strain-induced topological quantum phase transition in phosphorene oxide

Science.gov (United States)

Kang, Seoung-Hun; Park, Jejune; Woo, Sungjong; Kwon, Young-Kyun

Using ab initio density functional theory, we investigate the structural stability and electronic properties of phosphorene oxides (POx) with different oxygen compositions x. A variety of configurations are modeled and optimized geometrically to search for the equilibrium structure for each x value. Our electronic structure calculations on the equilibrium configuration obtained for each x reveal that the band gap tends to increase with the oxygen composition of x 0.5. We further explore the strain effect on the electronic structure of the fully oxidized phosphorene, PO, with x = 1. At a particular strain without spin-orbit coupling (SOC) is observed a band gap closure near the Γ point in the k space. We further find the strain in tandem with SOC induces an interesting band inversion with a reopened very small band gap (5 meV), and thus gives rise to a topological quantum phase transition from a normal insulator to a topological insulator. Such a topological phase transition is confirmed by the wave function analysis and the band topology identified by the Z2 invariant calculation.

Large magnetoresistance dips and perfect spin-valley filter induced by topological phase transitions in silicene

Science.gov (United States)

Prarokijjak, Worasak; Soodchomshom, Bumned

2018-04-01

Spin-valley transport and magnetoresistance are investigated in silicene-based N/TB/N/TB/N junction where N and TB are normal silicene and topological barriers. The topological phase transitions in TB's are controlled by electric, exchange fields and circularly polarized light. As a result, we find that by applying electric and exchange fields, four groups of spin-valley currents are perfectly filtered, directly induced by topological phase transitions. Control of currents, carried by single, double and triple channels of spin-valley electrons in silicene junction, may be achievable by adjusting magnitudes of electric, exchange fields and circularly polarized light. We may identify that the key factor behind the spin-valley current filtered at the transition points may be due to zero and non-zero Chern numbers. Electrons that are allowed to transport at the transition points must obey zero-Chern number which is equivalent to zero mass and zero-Berry's curvature, while electrons with non-zero Chern number are perfectly suppressed. Very large magnetoresistance dips are found directly induced by topological phase transition points. Our study also discusses the effect of spin-valley dependent Hall conductivity at the transition points on ballistic transport and reveals the potential of silicene as a topological material for spin-valleytronics.

Raman and loss induced quantum noise in depleted fiber optical parametric amplifiers

DEFF Research Database (Denmark)

Friis, Søren Michael Mørk; Rottwitt, Karsten; McKinstrie, C. J.

2013-01-01

We present a semi-classical approach for predicting the quantum noise properties of fiber optical parametric amplifiers. The unavoidable contributors of noise, vacuum fluctuations, loss-induced noise, and spontaneous Raman scattering, are included in the analysis of both phase-insensitive and phase...

Electroweak phase transitions

International Nuclear Information System (INIS)

Anderson, G.W.

1991-01-01

An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, left-angle φ right-angle T is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of left-angle φ right-angle T . In very minimal extensions of the standard model it is quite easy to increase left-angle φ right-angle T so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value left-angle φ right-angle = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state left-angle φ right-angle = 246 GeV unstable. The requirement that the state left-angle φ right-angle = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field

The dynamics of the laser-induced metal-semiconductor phase transition of samarium sulfide (SmS)

International Nuclear Information System (INIS)

Kaempfer, Tino

2009-01-01

The present thesis is dedicated to the experimental study of the metal-semiconductor phase transition of samarium sulfide (SmS): Temperature- and time-resolved experiments on the characterization of the phase transition of mixed-valence SmS samples (M-SmS) are presented. The measurement of the dynamics of the laser-induced phase transition pursues via time-resolved ultrashort-time microscopy and by X-ray diffraction with sub-picosecond time resolution. The electronic and structural processes, which follow an excitation of M-SmS with infrared femtosecond laser pulses, are physically interpreted on the base of the results obtained in this thesis and model imaginations. [de

Sensitivity analysis of the noise-induced oscillatory multistability in Higgins model of glycolysis

Science.gov (United States)

Ryashko, Lev

2018-03-01

A phenomenon of the noise-induced oscillatory multistability in glycolysis is studied. As a basic deterministic skeleton, we consider the two-dimensional Higgins model. The noise-induced generation of mixed-mode stochastic oscillations is studied in various parametric zones. Probabilistic mechanisms of the stochastic excitability of equilibria and noise-induced splitting of randomly forced cycles are analysed by the stochastic sensitivity function technique. A parametric zone of supersensitive Canard-type cycles is localized and studied in detail. It is shown that the generation of mixed-mode stochastic oscillations is accompanied by the noise-induced transitions from order to chaos.

Phase slip and telegraph noise in δ-MoN nanowires

Energy Technology Data Exchange (ETDEWEB)

Buh, Jože, E-mail: joze.buh@ijs.si [Jozef Stefan Institute, Department of Complex Matter, Jamova 39, SI-1000 Ljubljana (Slovenia); Mrzel, Aleš; Kovič, Andrej; Kabanov, Viktor [Jozef Stefan Institute, Department of Complex Matter, Jamova 39, SI-1000 Ljubljana (Slovenia); Jagličić, Zvonko [Institute of Mathematics, Physics and Mechanics, Jadranska 19, SI-1000 Ljubljana (Slovenia); University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova 2, SI-1000 Ljubljana (Slovenia); Vrtnik, Stanislav; Koželj, Primož [Jozef Stefan Institute, Jozef Stefan Institute, Department of Condensed Matter Physics, Jamova 39, SI-1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, Jozef Stefan Institute, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Mihailović, Dragan [Jozef Stefan Institute, Department of Complex Matter, Jamova 39, SI-1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, Jozef Stefan Institute, University of Ljubljana, SI-1000 Ljubljana (Slovenia); Jozef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana (Slovenia)

2017-04-15

Highlights: • Normal to SC transition width is strongly dependent on the diameter of the wire. • Telegraph noise frequency can be controlled by bias current. • Bias current is controlling the stability of different resistive states. • Magnetic field blurs of transitions between resistive superconducting states. - Abstract: We have investigated the effect of the nanowire thickness on the superconducting resistive phase transition R(T) in δ-MoN nanowires. We have characterized the width of the transition in terms of thermally-activated phase-slip theory. A large increase in the width of the transition was found with the decrease of the nanowire thickness. Discrete phase-slip fluctuations also lead to the appearance of meta-stable resistive superconducting states in current-bearing superconducting wires, with spontaneous switching between them. We have investigated the effect of the bias current on the switching rate and the stability of different resistive states.

Chicago transit authority train noise exposure.

Science.gov (United States)

Phan, Linh T; Jones, Rachael M

2017-06-01

To characterize noise exposure of riders on Chicago Transit Authority (CTA) trains, we measured noise levels twice on each segment of 7 of the 8 CTA train lines, which are named after colors, yielding 48 time-series measurements. We found the Blue Line has the highest noise levels compared to other train lines, with mean 76.9 dBA; and that the maximum noise level, 88.9 dBA occurred in the tunnel between the Chicago and Grand stations. Train segments involving travel through a tunnel had significantly higher noise levels than segments with travel on elevated and ground level tracks. While 8-hr doses inside the passenger cars were not estimated to exceed occupational exposure limits, train operators ride in a separate cab with operational windows and may therefore have higher noise exposures than riders. Despite the low risk of hearing loss for riders on CTA trains, in part because transit noise accounts for a small part of total daily noise exposure, 1-min average noise levels exceeded 85 dBA at times. This confirms anecdotal observations of discomfort due to noise levels, and indicates a need for noise management, particularly in tunnels.

Stochastic resonance induced by novel random transitions of motion of FitzHugh-Nagumo neuron model

International Nuclear Information System (INIS)

Zhang Guangjun; Xu Jianxue

2005-01-01

In contrast to the previous studies which have dealt with stochastic resonance induced by random transitions of system motion between two coexisting limit cycle attractors in the FitzHugh-Nagumo (FHN) neuron model after Hopf bifurcation and which have dealt with the phenomenon of stochastic resonance induced by external noise when the model with periodic input has only one attractor before Hopf bifurcation, in this paper we have focused our attention on stochastic resonance (SR) induced by a novel transition behavior, the transitions of motion of the model among one attractor on the left side of bifurcation point and two attractors on the right side of bifurcation point under the perturbation of noise. The results of research show: since one bifurcation of transition from one to two limit cycle attractors and the other bifurcation of transition from two to one limit cycle attractors occur in turn besides Hopf bifurcation, the novel transitions of motion of the model occur when bifurcation parameter is perturbed by weak internal noise; the bifurcation point of the model may stochastically slightly shift to the left or right when FHN neuron model is perturbed by external Gaussian distributed white noise, and then the novel transitions of system motion also occur under the perturbation of external noise; the novel transitions could induce SR alone, and when the novel transitions of motion of the model and the traditional transitions between two coexisting limit cycle attractors after bifurcation occur in the same process the SR also may occur with complicated behaviors types; the mechanism of SR induced by external noise when FHN neuron model with periodic input has only one attractor before Hopf bifurcation is related to this kind of novel transition mentioned above

Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

Energy Technology Data Exchange (ETDEWEB)

Bychkov, Igor V. [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kuzmin, Dmitry A., E-mail: kuzminda@csu.ru [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G. [Kotelnikov Institute of Radio-engineering and Electronics of RAS, Mokhovaya Street 11-7, Moscow 125009 (Russian Federation)

2016-11-01

In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii–Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii–Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications. - Highlights: • Magnetostrictive ultrasound generation by spiral magnets at phase transition (PT) is studied. • Spiral magnets during PT may generate transverse sound with wavelength equal to spiral period. • Amplitude of the sound is strictly depends on the phase transition speed. • Microwave-to-sound transformation in the vicinity of PT is investigated as well.

Dynamics of a quantum phase transition

International Nuclear Information System (INIS)

Zurek, W.H.

2005-01-01

We present two approaches to the non-equilibrium dynamics of a quench-induced phase transition in quantum Ising model. First approach retraces steps of the standard calculation to thermodynamic second order phase transitions in the quantum setting. The second calculation is purely quantum, based on the Landau-Zener formula for transition probabilities in processes that involve avoided level crossings. We show that the two approaches yield compatible results for the scaling of the defect density with the quench rate. We exhibit similarities between them, and comment on the insights they give into dynamics of quantum phase transitions. (author)

Mechanism of the monoclinic-to-tetragonal phase transition induced in zirconia and hafnia by swift heavy ions

International Nuclear Information System (INIS)

Benyagoub, Abdenacer

2005-01-01

Recent results demonstrated that defect formation or amorphization are not the only structural changes induced by swift heavy ions in crystalline materials and that under certain circumstances crystalline-to-crystalline phase transitions can also occur. For instance, it was found that both zirconia and hafnia transform from the monoclinic to the tetragonal phase with a kinetics involving a double ion impact process. In order to understand the origin of this ion-beam induced phase transition, the behavior of these twin oxides was analyzed and compared. In fact, the likeness of these materials offered the unique opportunity to impose drastic constraints on the possible models proposed to explain the creation of atomic displacements in the wake of swift heavy ions. This comparison clearly suggests that the thermal spike is the most appropriate process which governs the transition from the monoclinic to the tetragonal phase in zirconia and hafnia

Pressure-induced phase transitions in organic molecular crystals: a combination of x-ray single-crystal and powder diffraction, raman and IR-spectroscopy

International Nuclear Information System (INIS)

Boldyreva, E V; Goryainov, S V; Seryotkin, Y V; Kolesnik, E N; Shakhtshneider, T P; Ivashevskaya, S N; Drebushchak, T N; Sowa, H; Ahsbahs, H; Chernyshev, V V; Dmitriev, V P

2008-01-01

The contribution summarizes the results of recent studies of phase transitions induced by high pressure in a number of molecular organic crystals, such as polymorphs of paracetamol, chlorpropamide, polymorphs of glycine, L- and DL-serine, β-alanine. The main attention is paid to the following topics: (1) Reversible / irreversible transformations; (2) Different behavior of single crystals / powders; (3) The role of pressure-transmitting liquid; (4) The role of the kinetic factors: phase transitions on decompression, or after a long storage at a selected pressure; (5) Isosymmetric phase transitions; (6) The role of the changes in the hydrogen bond networks / intramolecular conformational changes in the phase transitions; (7) Superstructures / nanostructures formed as a result of pressure-induced phase transitions

Pressure-induced phase transitions in organic molecular crystals: a combination of x-ray single-crystal and powder diffraction, raman and IR-spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Boldyreva, E V; Goryainov, S V; Seryotkin, Y V; Kolesnik, E N; Shakhtshneider, T P; Ivashevskaya, S N; Drebushchak, T N [Research and Education Center ' Molecular Design and Ecologically Safe Technologies' , REC-008, Novosibirsk State University (Russian Federation); Sowa, H [Goettingen University (Germany); Ahsbahs, H; Chernyshev, V V [Marburg University (Germany); Dmitriev, V P [Swiss-Norwegian Beamline ESRF, Grenoble (France)], E-mail: boldyrev@nsu.ru

2008-07-15

The contribution summarizes the results of recent studies of phase transitions induced by high pressure in a number of molecular organic crystals, such as polymorphs of paracetamol, chlorpropamide, polymorphs of glycine, L- and DL-serine, {beta}-alanine. The main attention is paid to the following topics: (1) Reversible / irreversible transformations; (2) Different behavior of single crystals / powders; (3) The role of pressure-transmitting liquid; (4) The role of the kinetic factors: phase transitions on decompression, or after a long storage at a selected pressure; (5) Isosymmetric phase transitions; (6) The role of the changes in the hydrogen bond networks / intramolecular conformational changes in the phase transitions; (7) Superstructures / nanostructures formed as a result of pressure-induced phase transitions.

Phase Noise Compensation for OFDM Systems

Science.gov (United States)

Leshem, Amir; Yemini, Michal

2017-11-01

We describe a low complexity method for time domain compensation of phase noise in OFDM systems. We extend existing methods in several respects. First we suggest using the Karhunen-Lo\\'{e}ve representation of the phase noise process to estimate the phase noise. We then derive an improved datadirected choice of basis elements for LS phase noise estimation and present its total least square counterpart problem. The proposed method helps overcome one of the major weaknesses of OFDM systems. We also generalize the time domain phase noise compensation to the multiuser MIMO context. Finally we present simulation results using both simulated and measured phased noise. We quantify the tracking performance in the presence of residual carrier offset.

Probabilistic physical characteristics of phase transitions at highway bottlenecks: incommensurability of three-phase and two-phase traffic-flow theories.

Science.gov (United States)

Kerner, Boris S; Klenov, Sergey L; Schreckenberg, Michael

2014-05-01

Physical features of induced phase transitions in a metastable free flow at an on-ramp bottleneck in three-phase and two-phase cellular automaton (CA) traffic-flow models have been revealed. It turns out that at given flow rates at the bottleneck, to induce a moving jam (F → J transition) in the metastable free flow through the application of a time-limited on-ramp inflow impulse, in both two-phase and three-phase CA models the same critical amplitude of the impulse is required. If a smaller impulse than this critical one is applied, neither F → J transition nor other phase transitions can occur in the two-phase CA model. We have found that in contrast with the two-phase CA model, in the three-phase CA model, if the same smaller impulse is applied, then a phase transition from free flow to synchronized flow (F → S transition) can be induced at the bottleneck. This explains why rather than the F → J transition, in the three-phase theory traffic breakdown at a highway bottleneck is governed by an F → S transition, as observed in real measured traffic data. None of two-phase traffic-flow theories incorporates an F → S transition in a metastable free flow at the bottleneck that is the main feature of the three-phase theory. On the one hand, this shows the incommensurability of three-phase and two-phase traffic-flow theories. On the other hand, this clarifies why none of the two-phase traffic-flow theories can explain the set of fundamental empirical features of traffic breakdown at highway bottlenecks.

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

Directory of Open Access Journals (Sweden)

Sh. Ahmed Israa

2017-01-01

Full Text Available In this paper, we first review 2-D MDW code cross correlation equations and table to be improved significantly by using code correlation properties. These codes can be used in the synchronous optical CDMA systems for multi access interference cancellation and maximum suppress the phase induced intensity noise. Low Psr is due to the reduction of interference noise that is induced by the 2-D MDW code PIIN suppression. High data rate causes increases in BER, requires high effective power and severely deteriorates the system performance. The 2-D W/T MDW code has an excellent system performance where the value of PIIN is suppressed as low as possible at the optimum Psr with high data bit rate. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN maximally suppressed by MDW code through the minimizing property of cross correlation in comparison to 2-D PDC and 2-D MQC OCDMA code.scheme systems.

Two dimension MDW OCDMA code cross-correlation for reduction of phase induced intensity noise

Science.gov (United States)

Ahmed, Israa Sh.; Aljunid, Syed A.; Nordin, Junita M.; Dulaimi, Layth A. Khalil Al; Matem, Rima

2017-11-01

In this paper, we first review 2-D MDW code cross correlation equations and table to be improved significantly by using code correlation properties. These codes can be used in the synchronous optical CDMA systems for multi access interference cancellation and maximum suppress the phase induced intensity noise. Low Psr is due to the reduction of interference noise that is induced by the 2-D MDW code PIIN suppression. High data rate causes increases in BER, requires high effective power and severely deteriorates the system performance. The 2-D W/T MDW code has an excellent system performance where the value of PIIN is suppressed as low as possible at the optimum Psr with high data bit rate. The 2-D MDW code shows better tolerance to PIIN in comparison to others with enhanced system performance. We prove by numerical analysis that the PIIN maximally suppressed by MDW code through the minimizing property of cross correlation in comparison to 2-D PDC and 2-D MQC OCDMA code.scheme systems.

Parameter Diversity Induced Multiple Spatial Coherence Resonances and Spiral Waves in Neuronal Network with and Without Noise

International Nuclear Information System (INIS)

Li Yuye; Jia Bing; Gu Huaguang; An Shucheng

2012-01-01

Diversity in the neurons and noise are inevitable in the real neuronal network. In this paper, parameter diversity induced spiral waves and multiple spatial coherence resonances in a two-dimensional neuronal network without or with noise are simulated. The relationship between the multiple resonances and the multiple transitions between patterns of spiral waves are identified. The coherence degrees induced by the diversity are suppressed when noise is introduced and noise density is increased. The results suggest that natural nervous system might profit from both parameter diversity and noise, provided a possible approach to control formation and transition of spiral wave by the cooperation between the diversity and noise. (general)

Geometry-induced phase transition in fluids: capillary prewetting.

Science.gov (United States)

Yatsyshin, Petr; Savva, Nikos; Kalliadasis, Serafim

2013-02-01

We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangular pore exerting long-ranged dispersion forces on the fluid. In the T-μ plane the phase line of the new transition is tangential to the capillary condensation line at the capillary wetting temperature T(cw). The surface phase behavior of the system maps to planar wetting with the phase line of the new transition, termed capillary prewetting, mapping to the planar prewetting line. If capillary condensation is approached isothermally with T>T(cw), the meniscus forms at the capping wall and unbinds continuously, making capillary condensation a second-order phenomenon. We compute the corresponding critical exponent for the divergence of adsorption.

Pressure-induced anomalous phase transitions and colossal enhancement of piezoelectricity in PbTiO3.

Science.gov (United States)

Wu, Zhigang; Cohen, Ronald E

2005-07-15

We find an unexpected tetragonal-to-monoclinic-to-rhombohedral-to-cubic phase transition sequence induced by pressure, and a morphotropic phase boundary in a pure compound using first-principles calculations. Huge dielectric and piezoelectric coupling constants occur in the transition regions, comparable to those observed in the new complex single-crystal solid-solution piezoelectrics such as Pb(Mg(1/3)Nb(2/3))O3-PbTiO3, which are expected to revolutionize electromechanical applications. Our results show that morphotropic phase boundaries and giant piezoelectric effects do not require intrinsic disorder, and open the possibility of studying this effect in simple systems.

Group-velocity dispersion effects on quantum noise of a fiber optical soliton in phase space

International Nuclear Information System (INIS)

Ju, Heongkyu; Lee, Euncheol

2010-01-01

Group-velocity dispersion (GVD) effects on quantum noise of ultrashort pulsed light are theoretically investigated at the soliton energy level, using Gaussian-weighted pseudo-random distribution of phasors in phase space for the modeling of quantum noise properties including phase noise, photon number noise, and quantum noise shape in phase space. We present the effects of GVD that mixes the different spectral components in time, on the self-phase modulation(SPM)-induced quantum noise properties in phase space such as quadrature squeezing, photon-number noise, and tilting/distortion of quantum noise shape in phase space, for the soliton that propagates a distance of the nonlinear length η NL = 1/( γP 0 ) (P 0 is the pulse peak power and γ is the SPM parameter). The propagation dependence of phase space quantum noise properties for an optical soliton is also provided.

Hysteretic behavior of spin-crossover noise driven system

Energy Technology Data Exchange (ETDEWEB)

Gudyma, Iurii [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Maksymov, Artur, E-mail: maxyartur@gmail.com [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Advanced Materials Research Institute, University of New Orleans, LA 70148 (United States); Dimian, Mihai [Department of Electrical and Computer Engineering, Howard University, Washington DC, 20059 (United States); Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania)

2016-04-01

The influence of white Gaussian noise on hysteretic behavior of spin-crossover system is analyzed in the framework of stochastic Langevin dynamics. Various stochastic simulations are performed and several important properties of spin-transition in spin-crossover system driven by noise are reproduced. The numerical results are tested against the stationary probability function and the associated dynamic potential obtained from Fokker–Planck equation corresponding to spin-crossover Langevin dynamics. The dependence of light-induced optical hysteresis width and non-hysteretic transition curve slope on the noise intensity is illustrated. The role of low-spin and high-spin phase stabilities in the hysteretic behavior of noise-driven spin-crossover system is discussed.

Effects of noise in excitable systems

International Nuclear Information System (INIS)

Lindner, B.; Garcia-Ojalvo, J.; Neiman, A.; Schimansky-Geier, L.

2004-01-01

We review the behavior of theoretical models of excitable systems driven by Gaussian white noise. We focus mainly on those general properties of such systems that are due to noise, and present several applications of our findings in biophysics and lasers. As prototypes of excitable stochastic dynamics we consider the FitzHugh-Nagumo and the leaky integrate-and-fire model, as well as cellular automata and phase models. In these systems, taken as individual units or as networks of globally or locally coupled elements, we study various phenomena due to noise, such as noise-induced oscillations, stochastic resonance, stochastic synchronization, noise-induced phase transitions and noise-induced pulse and spiral dynamics. Our approach is based on stochastic differential equations and their corresponding Fokker-Planck equations, treated by both analytical calculations and/or numerical simulations. We calculate and/or measure the rate and diffusion coefficient of the excitation process, as well as spectral quantities like power spectra and degree of coherence. Combined with a multiparametric bifurcation analysis of the corresponding cumulant equations, these approaches provide a comprehensive picture of the multifaceted dynamical behaviour of noisy excitable systems

Pressure-induced irreversible metallization accompanying the phase transitions in S b2S3

Science.gov (United States)

Dai, Lidong; Liu, Kaixiang; Li, Heping; Wu, Lei; Hu, Haiying; Zhuang, Yukai; Yang, Linfei; Pu, Chang; Liu, Pengfei

2018-01-01

We have revealed S b2S3 to have two phase transitions and to undergo metallization using a diamond anvil cell at around 5.0, 15.0, and 34.0 GPa, respectively. These results were obtained on the basis of high-pressure Raman spectroscopy, temperature-dependent conductivity measurements, atomic force microscopy, high-resolution transmission electron microscopy, and first-principles calculations. The first phase transition at ˜5.0 GPa is an isostructural phase transition, which is manifested in noticeable changes in five Raman-active modes and the slope of the conductivity because of a change in the electronic structure. The second pressure-induced phase transition was characterized by a discontinuous change in the slope of conductivity and a new low-intensity Raman mode at ˜15.0 GPa . Furthermore, a semiconductor-to-metal transition was found at ˜34.0 GPa , which was accompanied by irreversible metallization, and it could be attributed to the permanently plastic deformation of the interlayer spacing. This high-pressure behavior of S b2S3 will help us to understand the universal crystal structure evolution and electrical characteristics for A2B3 -type compounds, and to facilitate their application in electronic devices.

Control of magnetic relaxation by electric-field-induced ferroelectric phase transition and inhomogeneous domain switching

Energy Technology Data Exchange (ETDEWEB)

Nan, Tianxiang; Emori, Satoru; Wang, Xinjun; Hu, Zhongqiang; Xie, Li; Gao, Yuan; Lin, Hwaider; Sun, Nian, E-mail: n.sun@neu.edu [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); Peng, Bin; Liu, Ming, E-mail: mingliu@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, Xi' an Jiaotong University, Xi' an 710049 (China); Jiao, Jie; Luo, Haosu [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Budil, David [Department of Chemistry, Northeastern University, Boston, Massachusetts 02115 (United States); Jones, John G.; Howe, Brandon M.; Brown, Gail J. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States)

2016-01-04

Electric-field modulation of magnetism in strain-mediated multiferroic heterostructures is considered a promising scheme for enabling memory and magnetic microwave devices with ultralow power consumption. However, it is not well understood how electric-field-induced strain influences magnetic relaxation, an important physical process for device applications. Here, we investigate resonant magnetization dynamics in ferromagnet/ferroelectric multiferroic heterostructures, FeGaB/PMN-PT and NiFe/PMN-PT, in two distinct strain states provided by electric-field-induced ferroelectric phase transition. The strain not only modifies magnetic anisotropy but also magnetic relaxation. In FeGaB/PMN-PT, we observe a nearly two-fold change in intrinsic Gilbert damping by electric field, which is attributed to strain-induced tuning of spin-orbit coupling. By contrast, a small but measurable change in extrinsic linewidth broadening is attributed to inhomogeneous ferroelastic domain switching during the phase transition of the PMN-PT substrate.

Lévy stable noise-induced transitions: stochastic resonance, resonant activation and dynamic hysteresis

International Nuclear Information System (INIS)

Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

2009-01-01

A standard approach to analysis of noise-induced effects in stochastic dynamics assumes a Gaussian character of the noise term describing interaction of the analyzed system with its complex surroundings. An additional assumption about the existence of timescale separation between the dynamics of the measured observable and the typical timescale of the noise allows external fluctuations to be modeled as temporally uncorrelated and therefore white. However, in many natural phenomena the assumptions concerning the above mentioned properties of 'Gaussianity' and 'whiteness' of the noise can be violated. In this context, in contrast to the spatiotemporal coupling characterizing general forms of non-Markovian or semi-Markovian Lévy walks, so called Lévy flights correspond to the class of Markov processes which can still be interpreted as white, but distributed according to a more general, infinitely divisible, stable and non-Gaussian law. Lévy noise-driven non-equilibrium systems are known to manifest interesting physical properties and have been addressed in various scenarios of physical transport exhibiting a superdiffusive behavior. Here we present a brief overview of our recent investigations aimed at understanding features of stochastic dynamics under the influence of Lévy white noise perturbations. We find that the archetypal phenomena of noise-induced ordering are robust and can be detected also in systems driven by memoryless, non-Gaussian, heavy-tailed fluctuations with infinite variance

ATR-IR spectroscopy for the detection of induced-phase transition in Langmuir-Blodgett monolayer film

International Nuclear Information System (INIS)

Widayati, Suci

1996-01-01

The rate at which a solid substrate is transferred through the Air/Water interface in the Langmuir-Blodgett process of preparing monomolecular films influences the final structure of the transferred film. This phenomenon has been observed from the attenuated total reflectance infra-red (ATR-IR) spectra of fatty acid monolayer transferred onto germanium substrate. This transfer-induced effect is most evidence when the monolayer is transferred from an expanded region of the surface-pressure-molecular area isotherm, but has limited influence on the hydrocarbon chain conformation of film molecules transferred in the condensed phases at high surface pressure. Such a conformational ordering may due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous sub phase. In addition, these results suggest that the structure of the amphiphilic molecules may modulate the extent and nature of the dipping-speed-induced structural changes taking place in the monomolecular L-B film. In order to use monomolecular L-B films to accurately characterize the structure, orientation and phase properties of monolayers at the Air/Water interface, the L-B transfer must be performed at transfer speeds that minimize this structural phase transition

Noise-induced transitions and resonant effects in nonlinear systems

Science.gov (United States)

Zaikin, Alexei

2003-02-01

Our every-day experience is connected with different acoustical noise or music. Usually noise plays the role of nuisance in any communication and destroys any order in a system. Similar optical effects are known: strong snowing or raining decreases quality of a vision. In contrast to these situations noisy stimuli can also play a positive constructive role, e.g. a driver can be more concentrated in a presence of quiet music. Transmission processes in neural systems are of especial interest from this point of view: excitation or information will be transmitted only in the case if a signal overcomes a threshold. Dr. Alexei Zaikin from the Potsdam University studies noise-induced phenomena in nonlinear systems from a theoretical point of view. Especially he is interested in the processes, in which noise influences the behaviour of a system twice: if the intensity of noise is over a threshold, it induces some regular structure that will be synchronized with the behaviour of neighbour elements. To obtain such a system with a threshold one needs one more noise source. Dr. Zaikin has analyzed further examples of such doubly stochastic effects and developed a concept of these new phenomena. These theoretical findings are important, because such processes can play a crucial role in neurophysics, technical communication devices and living sciences. Unsere alltägliche Erfahrung ist mit verschiedenen akustischen Einfluessen wie Lärm, aber auch Musik verbunden. Jeder weiss, wie Lärm stören kann und Kommunikation behindert oder gar unterbindet. Ähnliche optische Effekte sind bekannt: starkes Schneetreiben oder Regengüsse verschlechtern die Sicht und lassen uns Umrisse nur noch schemenhaft erkennen. Jedoch koennen ähnliche Stimuli auch sehr positive Auswirkungen haben: Autofahrer fahren bei leiser Musik konzentrierter -- die Behauptung von Schulkindern, nur bei dröhnenden Bässen die Mathehausaufgaben richtig rechnen zu können, ist allerdings nicht wissenschaftlich

The excitonic insulator route through a dynamical phase transition induced by an optical pulse

Energy Technology Data Exchange (ETDEWEB)

Brazovskii, S., E-mail: brazov@lptms.u-psud.fr [Université Paris-Saclay, LPTMS, CNRS, Univ. Paris-sud (France); Kirova, N. [Université Paris-Saclay, LPS, CNRS, Univ. Paris-sud (France)

2016-03-15

We consider a dynamical phase transition induced by a short optical pulse in a system prone to thermodynamical instability. We address the case of pumping to excitons whose density contributes directly to the order parameter. To describe both thermodynamic and dynamic effects on equal footing, we adopt a view of the excitonic insulator for the phase transition and suggest a formation of the Bose condensate for the pumped excitons. The work is motivated by experiments in donor–acceptor organic compounds with a neutral- ionic phase transition coupled to the spontaneous lattice dimerization and to charge transfer excitons. The double nature of the ensemble of excitons leads to an intricate time evolution, in particular, to macroscopic quantum oscillations from the interference between the Bose condensate of excitons and the ground state of the excitonic insulator. The coupling of excitons and the order parameter also leads to self-trapping of their wave function, akin to self-focusing in optics. The locally enhanced density of excitons can surpass a critical value to trigger the phase transformation, even if the mean density is below the required threshold. The system is stratified in domains that evolve through dynamical phase transitions and sequences of merging. The new circumstances in experiments and theory bring to life, once again, some remarkable inventions made by L.V. Keldysh.

Abating New York City transit noise: a matter of will, not way.

Science.gov (United States)

Bronzaft, Arline L

2010-01-01

From the latter part of the 19th century, when New York City trains began to operate, until the present time, New York City's Transit Authority has received train noise complaints from riders and residents living near its transit system. The growing body of literature demonstrating the adverse effects of noise on physical and mental health raises the question as to whether transit noise is hazardous to the health of New York City's transit riders and residents living near the transit system. Several studies have examined the impacts of the noise of New York's transit system on hearing, health and learning. Despite the Transit Authority's efforts to remedy transit noise in response to complaints, the noise problem has not yet been satisfactorily ameliorated. This paper will suggest how the Transit Authority could employ techniques that could lower the noise levels of its system and benefit the health and welfare of New Yorkers. The recommendations in this paper could also apply to other cities with major transit systems where noise abatement has not been treated seriously.

Abating New York city transit noise: A matter of will, not way

Directory of Open Access Journals (Sweden)

Arline L Bronzaft

2010-01-01

Full Text Available From the latter part of the 19 th century, when New York City trains began to operate, until the present time, New York City′s Transit Authority has received train noise complaints from riders and residents living near its transit system. The growing body of literature demonstrating the adverse effects of noise on physical and mental health raises the question as to whether transit noise is hazardous to the health of New York City′s transit riders and residents living near the transit system. Several studies have examined the impacts of the noise of New York′s transit system on hearing, health and learning. Despite the Transit Authority′s efforts to remedy transit noise in response to complaints, the noise problem has not yet been satisfactorily ameliorated. This paper will suggest how the Transit Authority could employ techniques that could lower the noise levels of its system and benefit the health and welfare of New Yorkers. The recommendations in this paper could also apply to other cities with major transit systems where noise abatement has not been treated seriously.

Phase transitions induced by the Aharonov-Bohm field

International Nuclear Information System (INIS)

Krive, I.V.; Naftulin, S.A.

1990-07-01

The influence of the Aharonov-Bohm flux (φ) on the order parameters of the 3-dimensional Gross-Neveu model and CP N -model in R 2 xS 1 space is considered. It is shown that the variation of flux causes the order parameter oscillations and for the small enough length of circular coordinate l c these oscillations attended with re-ordering phase transitions (i.e. the repeating transitions between the ordered and the disordered phases of the models in question). (author). 22 refs, 3 figs

Quantum phase transitions

International Nuclear Information System (INIS)

Sachdev, S.

1999-01-01

Phase transitions are normally associated with changes of temperature but a new type of transition - caused by quantum fluctuations near absolute zero - is possible, and can tell us more about the properties of a wide range of systems in condensed-matter physics. Nature abounds with phase transitions. The boiling and freezing of water are everyday examples of phase transitions, as are more exotic processes such as superconductivity and superfluidity. The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today. Phase transitions are traditionally classified as first or second order. In first-order transitions the two phases co-exist at the transition temperature - e.g. ice and water at 0 deg., or water and steam at 100 deg. In second-order transitions the two phases do not co-exist. In the last decade, attention has focused on phase transitions that are qualitatively different from the examples noted above: these are quantum phase transitions and they occur only at the absolute zero of temperature. The transition takes place at the ''quantum critical'' value of some other parameter such as pressure, composition or magnetic field strength. A quantum phase transition takes place when co-operative ordering of the system disappears, but this loss of order is driven solely by the quantum fluctuations demanded by Heisenberg's uncertainty principle. The physical properties of these quantum fluctuations are quite distinct from those of the thermal fluctuations responsible for traditional, finite-temperature phase transitions. In particular, the quantum system is described by a complex-valued wavefunction, and the dynamics of its phase near the quantum critical point requires novel theories that have no analogue in the traditional framework of phase transitions. In this article the author describes the history of quantum phase transitions. (UK)

A stress-induced phase transition model for semi-crystallize shape memory polymer

Science.gov (United States)

Guo, Xiaogang; Zhou, Bo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2014-03-01

The developments of constitutive models for shape memory polymer (SMP) have been motivated by its increasing applications. During cooling or heating process, the phase transition which is a continuous time-dependent process happens in semi-crystallize SMP and the various individual phases form at different temperature and in different configuration. Then, the transformation between these phases occurred and shape memory effect will emerge. In addition, stress applied on SMP is an important factor for crystal melting during phase transition. In this theory, an ideal phase transition model considering stress or pre-strain is the key to describe the behaviors of shape memory effect. So a normal distributed model was established in this research to characterize the volume fraction of each phase in SMP during phase transition. Generally, the experiment results are partly backward (in heating process) or forward (in cooling process) compared with the ideal situation considering delay effect during phase transition. So, a correction on the normal distributed model is needed. Furthermore, a nonlinear relationship between stress and phase transition temperature Tg is also taken into account for establishing an accurately normal distributed phase transition model. Finally, the constitutive model which taking the stress as an influence factor on phase transition was also established. Compared with the other expressions, this new-type model possesses less parameter and is more accurate. For the sake of verifying the rationality and accuracy of new phase transition and constitutive model, the comparisons between the simulated and experimental results were carried out.

Pressure-induced phase transition and octahedral tilt system change of Ba2BiSbO6

International Nuclear Information System (INIS)

Lufaso, Michael W.; Macquart, Rene B.; Lee, Yongjae; Vogt, Thomas; Loye, Hans-Conrad zur

2006-01-01

High-resolution X-ray synchrotron powder diffraction studies under high-pressure conditions are reported for the ordered double perovskite Ba 2 BiSbO 6 . Near 4GPa, the oxide undergoes a pressure-induced phase transition. The symmetry of the material changes during the phase transition from space group R3-bar to space group I2/m, which is consistent with a change in the octahedral tilting distortion from an a - a - a - type to a 0 b - b - type using the Glazer notation. A fit of the volume-pressure data using the Birch-Murnagaham equation of state yielded a bulk modulus of 144(8)GPa for the rhombohedral phase

Analyzing phase diagrams and phase transitions in networked competing populations

Science.gov (United States)

Ni, Y.-C.; Yin, H. P.; Xu, C.; Hui, P. M.

2011-03-01

Phase diagrams exhibiting the extent of cooperation in an evolutionary snowdrift game implemented in different networks are studied in detail. We invoke two independent payoff parameters, unlike a single payoff often used in most previous works that restricts the two payoffs to vary in a correlated way. In addition to the phase transition points when a single payoff parameter is used, phase boundaries separating homogeneous phases consisting of agents using the same strategy and a mixed phase consisting of agents using different strategies are found. Analytic expressions of the phase boundaries are obtained by invoking the ideas of the last surviving patterns and the relative alignments of the spectra of payoff values to agents using different strategies. In a Watts-Strogatz regular network, there exists a re-entrant phenomenon in which the system goes from a homogeneous phase into a mixed phase and re-enters the homogeneous phase as one of the two payoff parameters is varied. The non-trivial phase diagram accompanying this re-entrant phenomenon is quantitatively analyzed. The effects of noise and cooperation in randomly rewired Watts-Strogatz networks are also studied. The transition between a mixed phase and a homogeneous phase is identify to belong to the directed percolation universality class. The methods used in the present work are applicable to a wide range of problems in competing populations of networked agents.

Time-delay-induced phase-transition to synchrony in coupled bursting neurons

Science.gov (United States)

Adhikari, Bhim Mani; Prasad, Awadhesh; Dhamala, Mukeshwar

2011-06-01

Signal transmission time delays in a network of nonlinear oscillators are known to be responsible for a variety of interesting dynamic behaviors including phase-flip transitions leading to synchrony or out of synchrony. Here, we uncover that phase-flip transitions are general phenomena and can occur in a network of coupled bursting neurons with a variety of coupling types. The transitions are marked by nonlinear changes in both temporal and phase-space characteristics of the coupled system. We demonstrate these phase-transitions with Hindmarsh-Rose and Leech-Heart interneuron models and discuss the implications of these results in understanding collective dynamics of bursting neurons in the brain.

Twinning induced by the rhombohedral to orthorhombic phase transition in lanthanum gallate (LaGaO3)

Science.gov (United States)

Wang, W. L.; Lu, H. Y.

2006-10-01

Phase-transformation-induced twins in pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analysed using the transmission electron microscopy (TEM). Twins are induced by solid state phase transformation upon cooling from the rhombohedral (r, Rbar{3}c) to orthorhombic ( o, Pnma) symmetry at ˜145°C. Three types of transformation twins {101} o , {121} o , and {123} o were found in grains containing multiple domains that represent orientation variants. Three orthorhombic orientation variants were distinguished from the transformation domains converged into a triple junction. These twins are the reflection type as confirmed by tilting experiment in the microscope. Although not related by group-subgroup relation, the transformation twins generated by phase transition from rhombohedral to orthorhombic are consistent with those derived from taking cubic Pm {bar {3}}m aristotype of the lowest common supergroup symmetry as an intermediate metastable structure. The r→ o phase transition of first order in nature may have occurred by a diffusionless, martensitic-type or discontinuous nucleation and growth mechanism.

Phase Transitions in Geomorphology

Science.gov (United States)

Ortiz, C. P.; Jerolmack, D. J.

2015-12-01

Landscapes are patterns in a dynamic steady-state, due to competing processes that smooth or sharpen features over large distances and times. Geomorphic transport laws have been developed to model the mass-flux due to different processes, but are unreasonably effective at recovering the scaling relations of landscape features. Using a continuum approximation to compare experimental landscapes and the observed landscapes of the earth, one finds they share similar morphodynamics despite a breakdown of classical dynamical similarity between the two. We propose the origin of this effectiveness is a different kind of dynamic similarity in the statistics of initiation and cessation of motion of groups of grains, which is common to disordered systems of grains under external driving. We will show how the existing data of sediment transport points to common signatures with dynamical phase transitions between "mobile" and "immobile" phases in other disordered systems, particularly granular materials, colloids, and foams. Viewing landscape evolution from the lens of non-equilibrium statistical physics of disordered systems leads to predictions that the transition of bulk measurements such as particle flux is continuous from one phase to another, that the collective nature of the particle dynamics leads to very slow aging of bulk properties, and that the dynamics are history-dependent. Recent results from sediment transport experiments support these predictions, suggesting that existing geomorphic transport laws may need to be replaced by a new generation of stochastic models with ingredients based on the physics of disordered phase transitions. We discuss possible strategies for extracting the necessary information to develop these models from measurements of geomorphic transport noise by connecting particle-scale collective dynamics and space-time fluctuations over landscape features.

Noise-induced hearing loss: a recreational noise perspective.

Science.gov (United States)

Ivory, Robert; Kane, Rebecca; Diaz, Rodney C

2014-10-01

This review will discuss the real-world risk factors involved in noise-induced hearing loss as a result of common and popular recreational activities prone to mid and high levels of noise exposure. Although there are currently no interventional measures available to reverse or mitigate preexisting hearing loss from noise, we discuss the vital importance of hearing loss prevention from noise exposure avoidance and reduction. Despite a seeming understanding of the effects of noise exposure from various recreational activities and devices, a large percentage of the general public who is at risk of such noise-induced hearing loss still chooses to refrain from using hearing protection instruments. While occupational exposures pose the greatest traditional risk to hearing conservation in selected workers, recreational risk factors for noise-induced hearing loss may be more insidious in overall effect given the indifferent attitude of much of the general public and particularly our youths toward hearing protection during recreational activities. Active counseling regarding the consequences of excessive noise exposure and the potential benefits to hearing from usage of hearing protection instruments is critical to providing best possible care in the hearing health professions.

Noise-Induced Hearing Loss

Science.gov (United States)

... Home » Health Info » Hearing, Ear Infections, and Deafness Noise-Induced Hearing Loss On this page: What is ... I find additional information about NIHL? What is noise-induced hearing loss? Every day, we experience sound ...

Exceptional Points and Dynamical Phase Transitions

Directory of Open Access Journals (Sweden)

I. Rotter

2010-01-01

Full Text Available In the framework of non-Hermitian quantum physics, the relation between exceptional points,dynamical phase transitions and the counter intuitive behavior of quantum systems at high level density is considered. The theoretical results obtained for open quantum systems and proven experimentally some years ago on a microwave cavity, may explain environmentally induce deffects (including dynamical phase transitions, which have been observed in various experimental studies. They also agree(qualitatively with the experimental results reported recently in PT symmetric optical lattices.

Eigenstate Phase Transitions

Science.gov (United States)

Zhao, Bo

Phase transitions are one of the most exciting physical phenomena ever discovered. The understanding of phase transitions has long been of interest. Recently eigenstate phase transitions have been discovered and studied; they are drastically different from traditional thermal phase transitions. In eigenstate phase transitions, a sharp change is exhibited in properties of the many-body eigenstates of the Hamiltonian of a quantum system, but not the thermal equilibrium properties of the same system. In this thesis, we study two different types of eigenstate phase transitions. The first is the eigenstate phase transition within the ferromagnetic phase of an infinite-range spin model. By studying the interplay of the eigenstate thermalization hypothesis and Ising symmetry breaking, we find two eigenstate phase transitions within the ferromagnetic phase: In the lowest-temperature phase the magnetization can macroscopically oscillate by quantum tunneling between up and down. The relaxation of the magnetization is always overdamped in the remainder of the ferromagnetic phase, which is further divided into phases where the system thermally activates itself over the barrier between the up and down states, and where it quantum tunnels. The second is the many-body localization phase transition. The eigenstates on one side of the transition obey the eigenstate thermalization hypothesis; the eigenstates on the other side are many-body localized, and thus thermal equilibrium need not be achieved for an initial state even after evolving for an arbitrary long time. We study this many-body localization phase transition in the strong disorder renormalization group framework. After setting up a set of coarse-graining rules for a general one dimensional chain, we get a simple "toy model'' and obtain an almost purely analytical solution to the infinite-randomness critical fixed point renormalization group equation. We also get an estimate of the correlation length critical exponent nu

Stochastic multiresonance for a fractional linear oscillator with time-delayed kernel and quadratic noise

Science.gov (United States)

Guo, Feng; Wang, Xue-Yuan; Zhu, Cheng-Yin; Cheng, Xiao-Feng; Zhang, Zheng-Yu; Huang, Xu-Hui

2017-12-01

The stochastic resonance for a fractional oscillator with time-delayed kernel and quadratic trichotomous noise is investigated. Applying linear system theory and Laplace transform, the system output amplitude (SPA) for the fractional oscillator is obtained. It is found that the SPA is a periodical function of the kernel delayed-time. Stochastic multiplicative phenomenon appears on the SPA versus the driving frequency, versus the noise amplitude, and versus the fractional exponent. The non-monotonous dependence of the SPA on the system parameters is also discussed.

Mixed-order phase transition in a colloidal crystal

Science.gov (United States)

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-01

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field H. At the transition field Hs, the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length ξ∝|H2-Hs2|-1/2. Mean-field critical exponents are predicted, since the upper critical dimension of the transition is du=2. Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

Mixed-order phase transition in a colloidal crystal.

Science.gov (United States)

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-05

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field [Formula: see text] At the transition field [Formula: see text], the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length [Formula: see text] Mean-field critical exponents are predicted, since the upper critical dimension of the transition is [Formula: see text] Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

Frequency-dependent effects of background noise on subcortical response timing.

Science.gov (United States)

Tierney, A; Parbery-Clark, A; Skoe, E; Kraus, N

2011-12-01

The addition of background noise to an auditory signal delays brainstem response timing. This effect has been extensively documented using manual peak selection. Peak picking, however, is impractical for large-scale studies of spectrotemporally complex stimuli, and leaves open the question of whether noise-induced delays are frequency-dependent or occur across the frequency spectrum. Here we use an automated, objective method to examine phase shifts between auditory brainstem responses to a speech sound (/da/) presented with and without background noise. We predicted that shifts in neural response timing would also be reflected in frequency-specific phase shifts. Our results indicate that the addition of background noise causes phase shifts across the subcortical response spectrum (70-1000 Hz). However, this noise-induced delay is not uniform such that some frequency bands show greater shifts than others: low-frequency phase shifts (300-500 Hz) are largest during the response to the consonant-vowel formant transition (/d/), while high-frequency shifts (720-1000 Hz) predominate during the response to the steady-state vowel (/a/). Most importantly, phase shifts occurring in specific frequency bands correlate strongly with shifts in the latencies of the predominant peaks in the auditory brainstem response, while phase shifts in other frequency bands do not. This finding confirms the validity of phase shift detection as an objective measure of timing differences and reveals that this method detects noise-induced shifts in timing that may not be captured by traditional peak latency measurements. Copyright © 2011 Elsevier B.V. All rights reserved.

Noise in strong laser-atom interactions: Phase telegraph noise

International Nuclear Information System (INIS)

Eberly, J.H.; Wodkiewicz, K.; Shore, B.W.

1984-01-01

We discuss strong laser-atom interactions that are subjected to jump-type (random telegraph) random-phase noise. Physically, the jumps may arise from laser fluctuations, from collisions of various kinds, or from other external forces. Our discussion is carried out in two stages. First, direct and partially heuristic calculations determine the laser spectrum and also give a third-order differential equation for the average inversion of a two-level atom on resonance. At this stage a number of general features of the interaction are able to be studied easily. The optical analog of motional narrowing, for example, is clearly predicted. Second, we show that the theory of generalized Poisson processes allows laser-atom interactions in the presence of random telegraph noise of all kinds (not only phase noise) to be treated systematically, by means of a master equation first used in the context of quantum optics by Burshtein. We use the Burshtein equation to obtain an exact expression for the two-level atom's steady-state resonance fluorescence spectrum, when the exciting laser exhibits phase telegraph noise. Some comparisons are made with results obtained from other noise models. Detailed treatments of the effects ofmly jumps, or as a model of finite laser bandwidth effects, in which the laser frequency exhibits random jumps. We show that these two types of frequency noise can be distinguished in light-scattering spectra. We also discuss examples which demonstrate both temporal and spectral motional narrowing, nonexponential correlations, and non-Lorentzian spectra. Its exact solubility in finite terms makes the frequency-telegraph noise model an attractive alternative to the white-noise Ornstein-Uhlenbeck frequency noise model which has been previously applied to laser-atom interactions

Tricritical behaviour in the phase transition induced by electron-hole pairing

International Nuclear Information System (INIS)

Crisan, M.

1980-01-01

The electron-hole pairing, which is possible in metals or semiconductors, can give condensed phases with two order parameters. If the coupling between the two order parameters is considered, the free energy functional is similar with the free energy of a n-component spin system with cubic anisotropy. Using the Wagner hypothesis (tricritical scaling) the non-linear scaling fields have been calculated. In order to perform the calculation of the nonlinear fields we used the method given by Rudnick and Nelson to solve the recursion relations for the 4-epsilon-dimensional system with n=6 components. The present calculation in the frame-work of the renormalization-group approach confirms the result obtained in the mean-field theory that the coupling of the two order parameters induces a first order phase transition. (author)

Phase transitions

CERN Document Server

Sole, Ricard V; Solé, Ricard V; Solé, Ricard V; Sol, Ricard V; Solé, Ricard V

2011-01-01

Phase transitions--changes between different states of organization in a complex system--have long helped to explain physics concepts, such as why water freezes into a solid or boils to become a gas. How might phase transitions shed light on important problems in biological and ecological complex systems? Exploring the origins and implications of sudden changes in nature and society, Phase Transitions examines different dynamical behaviors in a broad range of complex systems. Using a compelling set of examples, from gene networks and ant colonies to human language and the degradation of diverse ecosystems, the book illustrates the power of simple models to reveal how phase transitions occur. Introductory chapters provide the critical concepts and the simplest mathematical techniques required to study phase transitions. In a series of example-driven chapters, Ricard Solé shows how such concepts and techniques can be applied to the analysis and prediction of complex system behavior, including the origins of ...

Structural phase transition in monolayer MoTe2 driven by electrostatic doping

Science.gov (United States)

Wang, Ying; Xiao, Jun; Zhu, Hanyu; Li, Yao; Alsaid, Yousif; Fong, King Yan; Zhou, Yao; Wang, Siqi; Shi, Wu; Wang, Yuan; Zettl, Alex; Reed, Evan J.; Zhang, Xiang

2017-10-01

Monolayers of transition-metal dichalcogenides (TMDs) exhibit numerous crystal phases with distinct structures, symmetries and physical properties. Exploring the physics of transitions between these different structural phases in two dimensions may provide a means of switching material properties, with implications for potential applications. Structural phase transitions in TMDs have so far been induced by thermal or chemical means; purely electrostatic control over crystal phases through electrostatic doping was recently proposed as a theoretical possibility, but has not yet been realized. Here we report the experimental demonstration of an electrostatic-doping-driven phase transition between the hexagonal and monoclinic phases of monolayer molybdenum ditelluride (MoTe2). We find that the phase transition shows a hysteretic loop in Raman spectra, and can be reversed by increasing or decreasing the gate voltage. We also combine second-harmonic generation spectroscopy with polarization-resolved Raman spectroscopy to show that the induced monoclinic phase preserves the crystal orientation of the original hexagonal phase. Moreover, this structural phase transition occurs simultaneously across the whole sample. This electrostatic-doping control of structural phase transition opens up new possibilities for developing phase-change devices based on atomically thin membranes.

Optically induced structural phase transitions in ion Coulomb crystals

DEFF Research Database (Denmark)

Horak, Peter; Dantan, Aurelien Romain; Drewsen, Michael

2012-01-01

We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures, such as b......We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures...

Strain-induced topological magnon phase transitions: applications to kagome-lattice ferromagnets

Science.gov (United States)

Owerre, S. A.

2018-06-01

A common feature of topological insulators is that they are characterized by topologically invariant quantity such as the Chern number and the index. This quantity distinguishes a nontrivial topological system from a trivial one. A topological phase transition may occur when there are two topologically distinct phases, and it is usually defined by a gap closing point where the topologically invariant quantity is ill-defined. In this paper, we show that the magnon bands in the strained (distorted) kagome-lattice ferromagnets realize an example of a topological magnon phase transition in the realistic parameter regime of the system. When spin–orbit coupling (SOC) is neglected (i.e. no Dzyaloshinskii–Moriya interaction), we show that all three magnon branches are dispersive with no flat band, and there exists a critical point where tilted Dirac and semi-Dirac point coexist in the magnon spectra. The critical point separates two gapless magnon phases as opposed to the usual phase transition. Upon the inclusion of SOC, we realize a topological magnon phase transition point at the critical strain , where D and J denote the perturbative SOC and the Heisenberg spin exchange interaction respectively. It separates two distinct topological magnon phases with different Chern numbers for and for . The associated anomalous thermal Hall conductivity develops an abrupt change at , due to the divergence of the Berry curvature in momentum space. The proposed topological magnon phase transition is experimentally feasible by applying external perturbations such as uniaxial strain or pressure.

Quantum phase transition with dissipative frustration

Science.gov (United States)

Maile, D.; Andergassen, S.; Belzig, W.; Rastelli, G.

2018-04-01

We study the quantum phase transition of the one-dimensional phase model in the presence of dissipative frustration, provided by an interaction of the system with the environment through two noncommuting operators. Such a model can be realized in Josephson junction chains with shunt resistances and resistances between the chain and the ground. Using a self-consistent harmonic approximation, we determine the phase diagram at zero temperature which exhibits a quantum phase transition between an ordered phase, corresponding to the superconducting state, and a disordered phase, corresponding to the insulating state with localized superconducting charge. Interestingly, we find that the critical line separating the two phases has a nonmonotonic behavior as a function of the dissipative coupling strength. This result is a consequence of the frustration between (i) one dissipative coupling that quenches the quantum phase fluctuations favoring the ordered phase and (ii) one that quenches the quantum momentum (charge) fluctuations leading to a vanishing phase coherence. Moreover, within the self-consistent harmonic approximation, we analyze the dissipation induced crossover between a first and second order phase transition, showing that quantum frustration increases the range in which the phase transition is second order. The nonmonotonic behavior is reflected also in the purity of the system that quantifies the degree of correlation between the system and the environment, and in the logarithmic negativity as an entanglement measure that encodes the internal quantum correlations in the chain.

Effects of signal modulation and coloured cross-correlation of coloured noises on the diffusion of a harmonic oscillator

Institute of Scientific and Technical Information of China (English)

Liu Li; Zhang Liang-Ying; Cao Li

2009-01-01

The diffusion in a harmonic oscillator driven by coloured noises ζ(t) and η(t) with coloured cross-correlation in which one of the noises is modulated by a biased periodic signal is investigated. The exact expression of diffusion coefficient d as a function of noise parameter, signal parameter, and oscillator frequency is derived. The findings in this paper are as follows. 1) The curves of d versus noise intensity D and d versus noises cross-correlation time τ_3 exist as two different phases. The transition between the two phases arises from the change of the cross-correlation coefficient λ of the two Orustein-Uhlenbeck (O-U) noises. 2) Changing the value of τ3, the curves of d versus Q, the intensity of colored noise that is modulated by the signal, can transform from a phase having a minimum to a monotonic phase. 3)Changing the value of signal amplitude A, d versus Q curves can transform from a phase having a minimum to a monotonic phase. The above-mentioned results demonstrate that a like noise-induced transition appears in the model.

Effects of signal modulation and coloured cross-correlation of coloured noises on the diffusion of a harmonic oscillator

International Nuclear Information System (INIS)

Li, Liu; Li, Cao; Liang-Ying, Zhang

2009-01-01

The diffusion in a harmonic oscillator driven by coloured noises ζ(t) and η(t) with coloured cross-correlation in which one of the noises is modulated by a biased periodic signal is investigated. The exact expression of diffusion coefficient d as a function of noise parameter, signal parameter, and oscillator frequency is derived. The findings in this paper are as follows. 1) The curves of d versus noise intensity D and d versus noises cross-correlation time τ 3 exist as two different phases. The transition between the two phases arises from the change of the cross-correlation coefficient λ of the two Ornstein–Uhlenbeck (O-U) noises. 2) Changing the value of τ 3 , the curves of d versus Q, the intensity of colored noise that is modulated by the signal, can transform from a phase having a minimum to a monotonic phase. 3) Changing the value of signal amplitude A, d versus Q curves can transform from a phase having a minimum to a monotonic phase. The above-mentioned results demonstrate that a like noise-induced transition appears in the model. (general)

Partial inertia induces additional phase transition in the majority vote model.

Science.gov (United States)

Harunari, Pedro E; de Oliveira, M M; Fiore, C E

2017-10-01

Explosive (i.e., discontinuous) transitions have aroused great interest by manifesting in distinct systems, such as synchronization in coupled oscillators, percolation regime, absorbing phase transitions, and more recently, the majority-vote model with inertia. In the latter, the model rules are slightly modified by the inclusion of a term depending on the local spin (an inertial term). In such a case, Chen et al. [Phys Rev. E 95, 042304 (2017)2470-004510.1103/PhysRevE.95.042304] have found that relevant inertia changes the nature of the phase transition in complex networks, from continuous to discontinuous. Here we give a further step by embedding inertia only in vertices with degree larger than a threshold value 〈k〉k^{*}, 〈k〉 being the mean system degree and k^{*} the fraction restriction. Our results, from mean-field analysis and extensive numerical simulations, reveal that an explosive transition is presented in both homogeneous and heterogeneous structures for small and intermediate k^{*}'s. Otherwise, a large restriction can sustain a discontinuous transition only in the heterogeneous case. This shares some similarities with recent results for the Kuramoto model [Phys. Rev. E 91, 022818 (2015)PLEEE81539-375510.1103/PhysRevE.91.022818]. Surprisingly, intermediate restriction and large inertia are responsible for the emergence of an extra phase, in which the system is partially synchronized and the classification of phase transition depends on the inertia and the lattice topology. In this case, the system exhibits two phase transitions.

Field induced magnetic phase transition as a magnon Bose Einstein condensation

Directory of Open Access Journals (Sweden)

Teodora Radu et al

2007-01-01

Full Text Available We report specific heat, magnetocaloric effect and magnetization measurements on single crystals of the frustrated quasi-2D spin -½ antiferromagnet Cs2CuCl4 in the external magnetic field 0≤B≤12 T along a-axis and in the temperature range 0.03 K≤T≤6 K. Decreasing the applied magnetic field B from high fields leads to the closure of the field induced gap in the magnon spectrum at a critical field Bcsimeq8.44 T and a long-range incommensurate state below Bc. In the vicinity of Bc, the phase transition boundary is well described by the power law TN~(Bc-B1/phi with the measured critical exponent phisimeq1.5. These findings provide experimental evidence that the scaling law of the transition temperature TN can be described by the universality class of 3D Bose–Einstein condensation (BEC of magnons.

Pressure induced structural phase transition in solid oxidizer KClO3: A first-principles study

Science.gov (United States)

Yedukondalu, N.; Ghule, Vikas D.; Vaitheeswaran, G.

2013-05-01

High pressure behavior of potassium chlorate (KClO3) has been investigated from 0 to 10 GPa by means of first principles density functional theory calculations. The calculated ground state parameters, transition pressure, and phonon frequencies using semiempirical dispersion correction scheme are in excellent agreement with experiment. It is found that KClO3 undergoes a pressure induced first order phase transition with an associated volume collapse of 6.4% from monoclinic (P21/m) → rhombohedral (R3m) structure at 2.26 GPa, which is in good accord with experimental observation. However, the transition pressure was found to underestimate (0.11 GPa) and overestimate (3.57 GPa) using local density approximation and generalized gradient approximation functionals, respectively. Mechanical stability of both the phases is explained from the calculated single crystal elastic constants. In addition, the zone center phonon frequencies have been calculated using density functional perturbation theory at ambient as well as at high pressure and the lattice modes are found to soften under pressure between 0.6 and 1.2 GPa. The present study reveals that the observed structural phase transition leads to changes in the decomposition mechanism of KClO3 which corroborates with the experimental results.

Defect-induced local variation of crystal phase transition temperature in metal-halide perovskites.

Science.gov (United States)

Dobrovolsky, Alexander; Merdasa, Aboma; Unger, Eva L; Yartsev, Arkady; Scheblykin, Ivan G

2017-06-26

Solution-processed organometal halide perovskites are hybrid crystalline semiconductors highly interesting for low-cost and efficient optoelectronics. Their properties are dependent on the crystal structure. Literature shows a variety of crystal phase transition temperatures and often a spread of the transition over tens of degrees Kelvin. We explain this inconsistency by demonstrating that the temperature of the tetragonal-to-orthorhombic phase transition in methylammonium lead triiodide depends on the concentration and nature of local defects. Phase transition in individual nanowires was studied by photoluminescence microspectroscopy and super-resolution imaging. We propose that upon cooling from 160 to 140 K, domains of the crystal containing fewer defects stay in the tetragonal phase longer than highly defected domains that readily transform to the high bandgap orthorhombic phase at higher temperatures. The existence of relatively pure tetragonal domains during the phase transition leads to drastic photoluminescence enhancement, which is inhomogeneously distributed across perovskite microcrystals.Understanding crystal phase transition in materials is of fundamental importance. Using luminescence spectroscopy and super-resolution imaging, Dobrovolsky et al. study the transition from the tetragonal to orthorhombic crystal phase in methylammonium lead triiodide nanowires at low temperature.

Temperature-induced phase transition in hydrogels of interpenetrating networks poly(N-isopropylmethacrylamide)/poly(N-isopropylacrylamide)

Czech Academy of Sciences Publication Activity Database

Šťastná, J.; Hanyková, L.; Sedláková, Zdeňka; Valentová, H.; Spěváček, Jiří

2013-01-01

Roč. 291, č. 10 (2013), s. 2409-2417 ISSN 0303-402X R&D Projects: GA ČR GA202/09/1281 Institutional support: RVO:61389013 Keywords : temperature-induced volume phase transition * poly (N-isopropylmethacrylamide) poly (Nisopropylacrylamide) interpenetrating network * 1H NMR spectroscopy Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.410, year: 2013

Magnetic-field induced phase transitions in intermetallic rare-earth ferrimagnets with a compensation point

Czech Academy of Sciences Publication Activity Database

Sabdenov, Ch.K.; Davydova, M.D.; Zvezdin, K.A.; Gorbunov, Denis; Tereshina, I. S.; Andreev, Alexander V.; Zvezdin, A. K.

2017-01-01

Roč. 43, č. 5 (2017), s. 551-558 ISSN 1063-777X R&D Projects: GA ČR GA16-03593S Institutional support: RVO:68378271 Keywords : rare-earth intermetallics * phase diagram * field-induced transition * magnetic anisotropy * high magnetic fields Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.804, year: 2016

Phase transitions in solids under high pressure

CERN Document Server

Blank, Vladimir Davydovich

2013-01-01

Phase equilibria and kinetics of phase transformations under high pressureEquipment and methods for the study of phase transformations in solids at high pressuresPhase transformations of carbon and boron nitride at high pressure and deformation under pressurePhase transitions in Si and Ge at high pressure and deformation under pressurePolymorphic α-ω transformation in titanium, zirconium and zirconium-titanium alloys Phase transformations in iron and its alloys at high pressure Phase transformations in gallium and ceriumOn the possible polymorphic transformations in transition metals under pressurePressure-induced polymorphic transformations in АIBVII compoundsPhase transformations in AIIBVI and AIIIBV semiconductor compoundsEffect of pressure on the kinetics of phase transformations in iron alloysTransformations during deformation at high pressure Effects due to phase transformations at high pressureKinetics and hysteresis in high-temperature polymorphic transformations under pressureHysteresis and kineti...

Cosmological phase transitions

International Nuclear Information System (INIS)

Kolb, E.W.

1993-10-01

If modern ideas about the role of spontaneous symmetry breaking in fundamental physics are correct, then the Universe should have undergone a series of phase transitions early in its history. The study of cosmological phase transitions has become an important aspect of early-Universe cosmology. In this lecture I review some very recent work on three aspects of phase transitions: the electroweak transition, texture, and axions

Monte Carlo Solutions for Blind Phase Noise Estimation

Directory of Open Access Journals (Sweden)

Çırpan Hakan

2009-01-01

Full Text Available This paper investigates the use of Monte Carlo sampling methods for phase noise estimation on additive white Gaussian noise (AWGN channels. The main contributions of the paper are (i the development of a Monte Carlo framework for phase noise estimation, with special attention to sequential importance sampling and Rao-Blackwellization, (ii the interpretation of existing Monte Carlo solutions within this generic framework, and (iii the derivation of a novel phase noise estimator. Contrary to the ad hoc phase noise estimators that have been proposed in the past, the estimators considered in this paper are derived from solid probabilistic and performance-determining arguments. Computer simulations demonstrate that, on one hand, the Monte Carlo phase noise estimators outperform the existing estimators and, on the other hand, our newly proposed solution exhibits a lower complexity than the existing Monte Carlo solutions.

Effects of phase transition induced density fluctuations on pulser dynamics

International Nuclear Information System (INIS)

Bagchi, Partha; Das, Arpan; Srivastava, Ajit M.; Layek, Biswanath

2016-01-01

We show that density fluctuations during phase transitions in pulsar cores may have non-trivial effects on pulsar timings, and may also possibly account for glitches and anti-glitches. These density fluctuations invariably lead to non-zero off-diagonal components of the moment of inertia, leading to transient wobbling of star. Thus, accurate measurements of pulsar timing and intensity modulations (from wobbling) may be used to identify the specific pattern of density fluctuations, hence the particular phase transition, occurring inside the pulsar core. Changes in quadrupole moment from rapidly evolving density fluctuations during the transition, with very short time scales, may provide a new source for gravitational waves. (author)

Effects of phase transition induced density fluctuations on pulsar dynamics

Directory of Open Access Journals (Sweden)

Partha Bagchi

2015-07-01

Full Text Available We show that density fluctuations during phase transitions in pulsar cores may have non-trivial effects on pulsar timings, and may also possibly account for glitches and anti-glitches. These density fluctuations invariably lead to non-zero off-diagonal components of the moment of inertia, leading to transient wobbling of star. Thus, accurate measurements of pulsar timing and intensity modulations (from wobbling may be used to identify the specific pattern of density fluctuations, hence the particular phase transition, occurring inside the pulsar core. Changes in quadrupole moment from rapidly evolving density fluctuations during the transition, with very short time scales, may provide a new source for gravitational waves.

Pressure-induced phase transition in KxFe2-yS2

International Nuclear Information System (INIS)

Tsuchiya, Yuu; Ikeda, Shugo; Kobayashi, Hisao; Zhang, Xiao-Wei; Kishimoto, Shunji; Kikegawa, Takumi; Hirao, Naohisa; Kawaguchi, Saori I.; Ohishi, Yasuo

2017-01-01

The structural and electronic properties of high-quality K 0.66(6) Fe 1.75(10) S 2 single crystals have been investigated by angle-resolved X-ray diffraction and 57 Fe nuclear forward scattering using synchrotron radiation under pressure at room temperature. The samples exhibit phase separation into antiferromagnetic ordered K 2 Fe 4 S 5 and nonmagnetic K x Fe 2 S 2 phases. It was found that a pressure-induced phase transition occurs at p c = 5.9(4) GPa with simultaneous suppression of the antiferromagnetic and Fe vacancy orders. >From the results of 57 Fe nuclear forward scattering, the refined magnetic hyperfine field remains unchanged with pressure below p c , suggesting that the Néel temperature does not decrease with pressure up to p c . Above p c , all Fe atoms in K 0.66 Fe 1.75 S 2 are in the same nonmagnetic state. A discontinuous increase in the center shift was observed at p c , reflecting a change in the Fe electronic state in K 0.66 Fe 1.75 S 2 . (author)

Time-Resolved Studies of Laser-Induced Phase Transitions in Gallium Arsenide

Science.gov (United States)

Siegal, Yakir

This thesis describes a series of time-resolved experiments of the linear and nonlinear optical properties of GaAs during laser-induced phase transitions. The first set of experiments consists of a direct determination of the behavior of the linear dielectric constant at photon energies of 2.2 eV and 4.4 eV following excitation of the sample with 1.9-eV, 70-fs laser pulses spanning a fluence range from 0 to 2.5 kJ/m^2. The results from this set of experiments were used to extract the behavior of the second-order optical susceptibility from second-harmonic generation measurements made under identical excitation conditions. These experiments are unique because they provide explicit information on the behavior of intrinsic material properties--the linear and nonlinear optical susceptibilities--during laser-induced phase transitions in semiconductors without the ambiguities in interpretation that are generally inherent in reflectivity and second-harmonic generation measurements. The dielectric constant data indicate a drop in the average bonding-antibonding splitting of GaAs following the laser pulse excitation. This behavior leads to a collapse of the band-gap on a picosecond time scale for excitation at fluences near the damage threshold of 1.0 kJ/m ^2 and even faster at higher excitation fluences. The changes in the electronic band structure result from a combination of electronic screening by the excited free carriers and structural deformation of the lattice caused by the destabilization of the covalent bonds. The behavior of the second-order susceptibility shows that the material loses long-range order before the average bonding-antibonding splitting, which is more sensitive to short-range structure, changes significantly. Loss of long-range order and a drop of more than 2 eV in the average bonding-antibonding splitting are seen even at fluences below the damage threshold, a regime in which the laser-induced changes are reversible.

Phase synchronization of neuronal noise in mouse hippocampal epileptiform dynamics.

Science.gov (United States)

Serletis, Demitre; Carlen, Peter L; Valiante, Taufik A; Bardakjian, Berj L

2013-02-01

Organized brain activity is the result of dynamical, segregated neuronal signals that may be used to investigate synchronization effects using sophisticated neuroengineering techniques. Phase synchrony analysis, in particular, has emerged as a promising methodology to study transient and frequency-specific coupling effects across multi-site signals. In this study, we investigated phase synchronization in intracellular recordings of interictal and ictal epileptiform events recorded from pairs of cells in the whole (intact) mouse hippocampus. In particular, we focused our analysis on the background noise-like activity (NLA), previously reported to exhibit complex neurodynamical properties. Our results show evidence for increased linear and nonlinear phase coupling in NLA across three frequency bands [theta (4-10 Hz), beta (12-30 Hz) and gamma (30-80 Hz)] in the ictal compared to interictal state dynamics. We also present qualitative and statistical evidence for increased phase synchronization in the theta, beta and gamma frequency bands from paired recordings of ictal NLA. Overall, our results validate the use of background NLA in the neurodynamical study of epileptiform transitions and suggest that what is considered "neuronal noise" is amenable to synchronization effects in the spatiotemporal domain.

Geometry-induced phase transition in fluids: Capillary prewetting

OpenAIRE

Yatsyshin, Petr; Savva, Nikos; Kalliadasis, Serafim

2013-01-01

We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangu...

Ultrafast optically induced ferromagnetic/anti-ferromagnetic phase transition in GdTiO3 from first principles

Science.gov (United States)

Khalsa, Guru; Benedek, Nicole A.

2018-03-01

Epitaxial strain and chemical substitution have been the workhorses of functional materials design. These static techniques have shown immense success in controlling properties in complex oxides through the tuning of subtle structural distortions. Recently, an approach based on the excitation of an infrared active phonon with intense midinfrared light has created an opportunity for dynamical control of structure through special nonlinear coupling to Raman phonons. We use first-principles techniques to show that this approach can dynamically induce a magnetic phase transition from the ferromagnetic ground state to a hidden antiferromagnetic phase in the rare earth titanate GdTiO3 for realistic experimental parameters. We show that a combination of a Jahn-Teller distortion, Gd displacement, and infrared phonon motion dominate this phase transition with little effect from the octahedral rotations, contrary to conventional wisdom.

High pressure structural phase transitions of TiO2 nanomaterials

International Nuclear Information System (INIS)

Li Quan-Jun; Liu Bing-Bing

2016-01-01

Recently, the high pressure study on the TiO 2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO 2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO 2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO 2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO 2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO 2 -B nanoribbons. Various TiO 2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO 2 nanoribbons, α -PbO 2 -type TiO 2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO 2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO 2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. (topical review)

Shear-induced structural transitions in Newtonian non-Newtonian two-phase flow

Science.gov (United States)

Cristobal, G.; Rouch, J.; Colin, A.; Panizza, P.

2000-09-01

We show the existence under shear flow of steady states in a two-phase region of a brine-surfactant system in which lyotropic dilute lamellar (non-Newtonian) and sponge (Newtonian) phases are coexisting. At high shear rates and low sponge phase-volume fractions, we report on the existence of a dynamic transition corresponding to the formation of a colloidal crystal of multilamellar vesicles (or ``onions'') immersed in the sponge matrix. As the sponge phase-volume fraction increases, this transition exhibits a hysteresis loop leading to a structural bistability of the two-phase flow. Contrary to single phase lamellar systems where it is always 100%, the onion volume fraction can be monitored continuously from 0 to 100 %.

Isostructural magnetic phase transition and magnetocaloric effect in Ising antiferromagnet

International Nuclear Information System (INIS)

Lavanov, G.Yu; Kalita, V.M.; Loktev, V.M.

2014-01-01

It is shown that the external magnetic field induced isostructural I st order magnetic phase transition between antiferromagnetic phases with different antiferromagnetic vector values is associated with entropy. It is found, that depending on temperature the entropy jump and the related heat release change their sign at this transition point. In the low-temperature region of metamagnetic I st order phase tensition the entropy jump is positive, and in the triple point region this jump for isostructural magnetic transition is negative

Activity induced phase transition in mixtures of active and passive agents

Science.gov (United States)

Sinha Mahapatra, Pallab; Kulkarni, Ajinkya

2017-11-01

Collective behaviors of self-propelling agents are ubiquitous in nature that produces interesting patterns. The objective of this study is to investigate the phase transition in mixtures of active and inert agents suspended in a liquid. A modified version of the Vicsek Model has been used (see Ref.), where the particles are modeled as soft disks with finite mass, confined in a square domain. The particles are required to align their local motion to their immediate neighborhood, similar to the Vicsek model. We identified the transition from disorganized thermal-like motion to an organized vortical motion. We analyzed the nature of the transition by using different order parameters. Furthermore the switching between the phases has been investigated via artificial nucleation of randomly picked active agents spanning the entire domain. Finally the motivation for this phase transition has been explained via average dissipation and the mean square displacement (MSD) of the agents.

Cosmological phase transitions

International Nuclear Information System (INIS)

Kolb, E.W.

1987-01-01

If the universe stated from conditions of high temperature and density, there should have been a series of phase transitions associated with spontaneous symmetry breaking. The cosmological phase transitions could have observable consequences in the present Universe. Some of the consequences including the formation of topological defects and cosmological inflation are reviewed here. One of the most important tools in building particle physics models is the use of spontaneous symmetry breaking (SSB). The proposal that there are underlying symmetries of nature that are not manifest in the vacuum is a crucial link in the unification of forces. Of particular interest for cosmology is the expectation that are the high temperatures of the big bang symmetries broken today will be restored, and that there are phase transitions to the broken state. The possibility that topological defects will be produced in the transition is the subject of this section. The possibility that the Universe will undergo inflation in a phase transition will be the subject of the next section. Before discussing the creation of topological defects in the phase transition, some general aspects of high-temperature restoration of symmetry and the development of the phase transition will be reviewed. 29 references, 1 figure, 1 table

Generalized transport model for phase transition with memory

International Nuclear Information System (INIS)

Chen, Chi; Ciucci, Francesco

2013-01-01

A general model for phenomenological transport in phase transition is derived, which extends Jäckle and Frisch model of phase transition with memory and the Cahn–Hilliard model. In addition to including interfacial energy to account for the presence of interfaces, we introduce viscosity and relaxation contributions, which result from incorporating memory effect into the driving potential. Our simulation results show that even without interfacial energy term, the viscous term can lead to transient diffuse interfaces. From the phase transition induced hysteresis, we discover different energy dissipation mechanism for the interfacial energy and the viscosity effect. In addition, by combining viscosity and interfacial energy, we find that if the former dominates, then the concentration difference across the phase boundary is reduced; conversely, if the interfacial energy is greater then this difference is enlarged.

Stratification-induced order--disorder phase transitions in molecularly thin confined films

International Nuclear Information System (INIS)

Schoen, M.; Diestler, D.J.; Cushman, J.H.

1994-01-01

By means of grand canonical ensemble Monte Carlo simulations of a monatomic film confined between unstructured (i.e., molecularly smooth) rigidly fixed solid surfaces (i.e., walls), we investigate the mechanism of molecular stratification, i.e., the tendency of atoms to arrange themselves in layers parallel with the walls. Stratification is accompanied by a heretofore unnoticed order--disorder phase transition manifested as a maximum in density fluctuations at the transition point. The transition involves phases with different transverse packing characteristics, although the number of layers accommodated between the walls remains unchanged during the transition, which occurs periodically as the film thickens. However, with increasing thickness, an increasingly smaller proportion of the film is structurally affected by the transition. Thus, the associated maximum in density fluctuations diminishes rapidly with film thickness

Phase-dependent noise in Josephson junctions

Science.gov (United States)

Sheldon, Forrest; Peotta, Sebastiano; Di Ventra, Massimiliano

2018-03-01

In addition to the usual superconducting current, Josephson junctions (JJs) support a phase-dependent conductance related to the retardation effect of tunneling quasi-particles. This introduces a dissipative current with a memory-resistive (memristive) character that should also affect the current noise. By means of the microscopic theory of tunnel junctions we compute the complete current autocorrelation function of a Josephson tunnel junction and show that this memristive component gives rise to both a previously noted phase-dependent thermal noise, and an undescribed non-stationary, phase-dependent dynamic noise. As experiments are approaching ranges in which these effects may be observed, we examine the form and magnitude of these processes. Their phase dependence can be realized experimentally as a hysteresis effect and may be used to probe defects present in JJ based qubits and in other superconducting electronics applications.

Noise Spectroscopy in Strongly Correlated Oxides

Science.gov (United States)

Alsaqqa, Ali M.

Strongly correlated materials are an interesting class of materials, thanks to the novel electronic and magnetic phenomena they exhibit as a result of the interplay of various degrees of freedom. This gives rise to an array of potential applications, from Mott-FET to magnetic storage. Many experimental probes have been used to study phase transitions in strongly correlated oxides. Among these, resistance noise spectroscopy, together with conventional transport measurements, provides a unique viewpoint to understand the microscopic dynamics near the phase transitions in these oxides. In this thesis, utilizing noise spectroscopy and transport measurements, four different strongly correlated materials were studied: (1) neodymium nickel oxide (NdNiO 3) ultrathin films, (2) vanadium dioxide (VO2) microribbons, (3) copper vanadium bronze (CuxV2O 5) microribbons and (4) niobium triselenide (NbSe3) microribbons. Ultra thin films of rare-earth nickelates exhibit several temperature-driven phase transitions. In this thesis, we studied the metal-insulator and Neel transitions in a series of NdNiO3 films with different lattice mismatches. Upon colling down, the metal-insulator phase transition is accompanied by a structural (orthorohombic to monoclinic) and magnetic (paramagnetic to antiferromagnetic) transitions as well, making the problem more interesting and complex at the same time. The noise is of the 1/f type and is Gaussian in the high temperature phase, however deviations are seen in the low temperature phases. Below the metal-insulator transition, noise magnitude increases by orders of magnitude: a sign of inhomogeneous electrical conduction as result of phase separation. This is further assured by the non-Gaussian noise signature. At very low temperatures (T switches between Gaussian and non-Gaussian over several hours, possibly arising from dynamically competing ground states. VO2 is one of the most widely studied strongly correlated oxides and is important from the

Chaos Noise on Phase of Van Der Pol Oscillator

Directory of Open Access Journals (Sweden)

Xian He Huang

2010-12-01

Full Text Available Phase noise is the most important parameter in many oscillators. In this paper, based on nonlinear stochastic differential equation for phase noise analysis approach is proposed. And then discusses and compares the influence of two different sources of noise in the Van Der Pol oscillator adopted this method. One source of noise is a white noise process, which is a genuinely stochastic process; the other source of noise is actually a deterministic system, which exhibits chaotic behavior in some regions. The behavior of the oscillator under different conditions is investigated numerically. It is shown that the phase noise of the oscillator is affected more by noise arising from chaos than by noise arising from the genuine stochastic process at the same noise intensity.

Variable-temperature Microwave Impedance Microscope with Light Stimulation for Research on Photo-induced Phase Transitions

Science.gov (United States)

2017-07-24

SECURITY CLASSIFICATION OF: The DURIP program "Variable-temperature Microwave Impedance Microscope with Light Stimulation for Research on Photo... Stimulation for Research on Photo- induced Phase Transitions The views, opinions and/or findings contained in this report are those of the author(s) and should...reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions

Evaluation of stress-induced martensite phase in ferromagnetic shape memory alloy Fe-30.2at%Pd by non-destructive Barkhausen noise

Science.gov (United States)

Furuya, Yasubumi; Okazaki, Teiko; Ueno, Takasi; Spearing, Mark; Wutting, Manfred

2005-05-01

Barkhausen noise (BHN) method seems a useful tecnique to non-destructive evaluation of martensite phase transformation of ferromagnetic shape memory alloy, which is used as the filler of our proposing "Smart Composite Board". The concept of design for "Smart Composite Board" which can combine the non-destructive magnetic inspection and shape recovery function in the material itself was formerly proposed. In the present study, we survey the possibility of Barkhausen noise (BHN) method to detect the transformation of microscopic martensite phase caused by stress-loading in Fe-30.2at%Pd thin foil, which has a stable austenite phase (fcc structure) at room temperature. The BHN voltage was measured at loading stress up to 100 MPa in temperature range of 300K to 373K. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. A phase transformation caused by loading stress were analyzed also by X-ray diffraction. The signals of BHN are analyzed by the time of magnetization and the noise frequency. BHN caused by grain boundaries appears in the lower frequency range (1kHz-3kHz) and BHN by martensite twin in the higher frequency range (8kHz-10kHz). The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.

Stochastic systems with cross-correlated Gaussian white noises

International Nuclear Information System (INIS)

Wang Cheng-Yu; Song Yu-Min; Zhou Peng; Yang Hai; Gao Yun

2010-01-01

This paper theoretically investigates three stochastic systems with cross-correlation Gaussian white noises. Both steady state properties of the stochastic nonlinear systems and the nonequilibrium transitions induced by the cross-correlated noises are studied. The stationary solutions of the Fokker—Planck equation for three specific examples are analysed. It is shown explicitly that the cross-correlation of white noises can induce nonequilibrium transitions

Pressure-induced phase transitions in Zr-rich PbZr{sub 1-x}Ti{sub x}O{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Souza Filho, A.G. [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza, Ceara (Brazil)]. E-mail: agsf@fisica.ufc.br; Faria, J.L.B.; Freire, P.T.C.; Ayala, A.P.; Sasaki, J.M.; Melo, F.E.A.; Mendes Filho, J. [Departamento de Fisica, Universidade Federal do Ceara, Fortaleza, Ceara (Brazil); Araujo, E.B. [Departamento de Fisica e Quimica, Universidade Estadual de Sao Paulo, Campus de Ilha Solteira, Ilha Solteira, SP (Brazil); Eiras, J.A. [Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)

2001-08-20

A Raman study of structural changes in the Zr-rich PbZr{sub 1-x}Ti{sub x}O{sub 3} (PZT) system under hydrostatic pressures up to 5.0 GPa is presented. We observe that externally applied pressure induces several phase transitions in PZT ceramics among phases with orthorhombic (A{sub O}), rhombohedral low-temperature (R{sub LT}), and rhombohedral high-temperature (R{sub HT}) symmetries (all found in PZT at ambient pressure and room temperature). Each of the compositions investigated (0.02{<=}x{<=}0.14) exhibits a high-pressure phase with orthorhombic (O{sub I'}) symmetry. We further report a detailed study of the pressure dependence of Raman frequencies to elucidate the phase transitions and to provide a set of pressure coefficients for the high-pressure phases. (author)

Stochastic IMT (Insulator-Metal-Transition Neurons: An Interplay of Thermal and Threshold Noise at Bifurcation

Directory of Open Access Journals (Sweden)

Abhinav Parihar

2018-04-01

Full Text Available Artificial neural networks can harness stochasticity in multiple ways to enable a vast class of computationally powerful models. Boltzmann machines and other stochastic neural networks have been shown to outperform their deterministic counterparts by allowing dynamical systems to escape local energy minima. Electronic implementation of such stochastic networks is currently limited to addition of algorithmic noise to digital machines which is inherently inefficient; albeit recent efforts to harness physical noise in devices for stochasticity have shown promise. To succeed in fabricating electronic neuromorphic networks we need experimental evidence of devices with measurable and controllable stochasticity which is complemented with the development of reliable statistical models of such observed stochasticity. Current research literature has sparse evidence of the former and a complete lack of the latter. This motivates the current article where we demonstrate a stochastic neuron using an insulator-metal-transition (IMT device, based on electrically induced phase-transition, in series with a tunable resistance. We show that an IMT neuron has dynamics similar to a piecewise linear FitzHugh-Nagumo (FHN neuron and incorporates all characteristics of a spiking neuron in the device phenomena. We experimentally demonstrate spontaneous stochastic spiking along with electrically controllable firing probabilities using Vanadium Dioxide (VO2 based IMT neurons which show a sigmoid-like transfer function. The stochastic spiking is explained by two noise sources - thermal noise and threshold fluctuations, which act as precursors of bifurcation. As such, the IMT neuron is modeled as an Ornstein-Uhlenbeck (OU process with a fluctuating boundary resulting in transfer curves that closely match experiments. The moments of interspike intervals are calculated analytically by extending the first-passage-time (FPT models for Ornstein-Uhlenbeck (OU process to include a

Phase noise and frequency stability in oscillators

CERN Document Server

Rubiola, Enrico

2009-01-01

Presenting a comprehensive account of oscillator phase noise and frequency stability, this practical text is both mathematically rigorous and accessible. An in-depth treatment of the noise mechanism is given, describing the oscillator as a physical system, and showing that simple general laws govern the stability of a large variety of oscillators differing in technology and frequency range. Inevitably, special attention is given to amplifiers, resonators, delay lines, feedback, and flicker (1/f) noise. The reverse engineering of oscillators based on phase-noise spectra is also covered, and end-of-chapter exercises are given. Uniquely, numerous practical examples are presented, including case studies taken from laboratory prototypes and commercial oscillators, which allow the oscillator internal design to be understood by analyzing its phase-noise spectrum. Based on tutorials given by the author at the Jet Propulsion Laboratory, international IEEE meetings, and in industry, this is a useful reference for acade...

Shear-induced transitions in a ternary polymeric system

NARCIS (Netherlands)

Zvelindovsky, AV; Sevink, GJA; Fraaije, JGEM

The first three-dimensional simulation of shear-induced phase transitions in a polymeric system has been performed. The method is based on dynamic density-functional theory. The pathways between a bicontinuous phase with developing gyroid mesostructure and a lamellar/cylinder phase coexistence are

Pressure induced structural phase transition of OsB 2: First-principles calculations

Science.gov (United States)

Ren, Fengzhu; Wang, Yuanxu; Lo, V. C.

2010-04-01

Orthorhombic OsB 2 was synthesized at 1000 °C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB 2. An analysis of the calculated enthalpy shows that orthorhombic OsB 2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 6 3/ mmc structure (high-pressure phase) is stable for OsB 2. We expect the phase transition can be further confirmed by the experimental work.

Electrically induced phase transition in GeSbTe alloys

Energy Technology Data Exchange (ETDEWEB)

Bruns, Gunnar; Schlockermann, Carl; Woda, Michael; Wuttig, Matthias [I. Physikalisches Institut Ia, RWTH Aachen, 52056 Aachen (Germany)

2008-07-01

While phase change materials have already successfully been applied in rewriteable optical data storage, they are now also promising to form the basis for novel non-volatile electrical data storage devices. To understand the physical concepts of these so-called Phase Change Random Access Memory (PCRAM) it is mandatory to gain a deeper insight into the switching process between the highly resistive amorphous and the lowly resistive crystalline phase. The fast phase transitions between the amorphous and crystalline state of GeSbTe-based alloys has so far often been studied using pulsed laser irradiation. In this work an alternative approach is employed to investigate this transition. Electrical pulses are used to rapidly and reversibly switch between the two states. For these experiments a setup was built with a specially designed contacting circuit board to meet the requirements of electrical measurements on a nanosecond timescale. The influence of the pulse parameters on the change of device resistance was determined for different initial states. Furthermore the high time resolution of 0.4 ns allows investigation of transient electrical effects like the so-called threshold switching first described by Ovshinsky in the late 1960s.

Electrically induced phase transition in GeSbTe alloys

International Nuclear Information System (INIS)

Bruns, Gunnar; Schlockermann, Carl; Woda, Michael; Wuttig, Matthias

2008-01-01

While phase change materials have already successfully been applied in rewriteable optical data storage, they are now also promising to form the basis for novel non-volatile electrical data storage devices. To understand the physical concepts of these so-called Phase Change Random Access Memory (PCRAM) it is mandatory to gain a deeper insight into the switching process between the highly resistive amorphous and the lowly resistive crystalline phase. The fast phase transitions between the amorphous and crystalline state of GeSbTe-based alloys has so far often been studied using pulsed laser irradiation. In this work an alternative approach is employed to investigate this transition. Electrical pulses are used to rapidly and reversibly switch between the two states. For these experiments a setup was built with a specially designed contacting circuit board to meet the requirements of electrical measurements on a nanosecond timescale. The influence of the pulse parameters on the change of device resistance was determined for different initial states. Furthermore the high time resolution of 0.4 ns allows investigation of transient electrical effects like the so-called threshold switching first described by Ovshinsky in the late 1960s

Theoretical studies of the pressure-induced zinc-blende to cinnabar phase transition in CdTe and thermodynamical properties of each phase

International Nuclear Information System (INIS)

Brik, M.G.; Łach, P.; Karczewski, G.; Wojtowicz, T.; Kamińska, A.; Suchocki, A.

2013-01-01

Luminescence of CdTe quantum dots embedded in ZnTe is quenched at pressure of about 4.5 GPa in the high-pressure experiments. This pressure-induced quenching is attributed to the “zinc-blende–cinnabar” phase transition in CdTe, which was confirmed by the first-principles calculations. Theoretical analysis of the pressure at which the phase transition occurs for CdTe was performed using the CASTEP module of Materials Studio package with both generalized gradient approximation (GGA) and local density approximation (LDA). The calculated phase transition pressures are equal to about 4.4 GPa and 2.6 GPa, according to the GGA and LDA calculations, respectively, which is in a good agreement with the experimental value. Theoretically estimated value of the pressure coefficient of the band-gap luminescence in zinc-blende structure is in very good agreement with that recently measured in the QDs structures. The calculated Debye temperature, elastic constants and specific heat capacity for the zinc-blend structure agree well with the experimental data; the data for the cinnabar phase are reported here for the first time to the best of the authors' knowledge. - Highlights: • Quenching of luminescence of CdTe quantum dots embedded in ZnTe is theoretically explained. • The theoretical calculation of elastic and thermodynamic properties of CdTe by two types of ab-initio methods. • Theoretical calculations of some optical properties of CdTe under pressure in zinc-blende and cinnabar phases

No large scale curvature perturbations during the waterfall phase transition of hybrid inflation

International Nuclear Information System (INIS)

Abolhasani, Ali Akbar; Firouzjahi, Hassan

2011-01-01

In this paper the possibility of generating large scale curvature perturbations induced from the entropic perturbations during the waterfall phase transition of the standard hybrid inflation model is studied. We show that whether or not appreciable amounts of large scale curvature perturbations are produced during the waterfall phase transition depends crucially on the competition between the classical and the quantum mechanical backreactions to terminate inflation. If one considers only the classical evolution of the system, we show that the highly blue-tilted entropy perturbations induce highly blue-tilted large scale curvature perturbations during the waterfall phase transition which dominate over the original adiabatic curvature perturbations. However, we show that the quantum backreactions of the waterfall field inhomogeneities produced during the phase transition dominate completely over the classical backreactions. The cumulative quantum backreactions of very small scale tachyonic modes terminate inflation very efficiently and shut off the curvature perturbation evolution during the waterfall phase transition. This indicates that the standard hybrid inflation model is safe under large scale curvature perturbations during the waterfall phase transition.

Current-phase relations and noise in rf biased SQUIDS

International Nuclear Information System (INIS)

Jackel, L.D.; Clark, T.D.; Buhrman, R.A.

1975-01-01

An investigation was made of the effect of the weak link current-phase relation on noise in rf biased SQUIDs. Non-sinusoidal current-phase relations were observed in various weak links, and these non-sinusoidal relations were correlated with significantly increased intrinsic noise in the SQUID ring. The current-phase relation was also found to affect the amplitude of the rf SQUID ring dissipation. The result of an rf SQUID system noise analysis shows that, due to increased intrinsic noise and reduced ring dissipation, the minimum attainable noise for a SQUID ring having a very non-sinusoidal current-phase relation is considerably greater than for a ring with a sinusoidal relation

Field-induced phase transitions in antiferromagnetic systems

International Nuclear Information System (INIS)

Smeets, J.P.M.

1984-05-01

Neutron scattering experiments and magnetization measurements are carried out on cobalt bromide hexahydrate, of which 48% of the water molecules are replaced by deuterium oxide molecules. Results were compared with data obtained from non-deuterated cobalt bromide hexahydrate. Neutron scattering experiments showed the importance of the deuterium fraction. Interplay exists between the crystallographic system and the magnetic system, which is influenced by changing the deuterium fraction. Neutron scattering and magnetization experiments on partially deuterated RbFeCl 3 .2H 2 O and CsFeCl 3 .2H 2 O were performed to study the magnetic phase transitions in these quasi one-dimensional Ising compounds. The observed behaviour in the various phases can be described by the nucleation theory of chain reversals. (Auth.)

A theoretical study of pressure-induced phase transitions and electronic band structure of anti-A-sesquioxide type γ-Be3N2

International Nuclear Information System (INIS)

Paliwal, Uttam; Joshi, Kunj Bihari

2011-01-01

Structural parameters and electronic band structure of anti-A-sesquioxide (aAs) type γ-Be 3 N 2 are presented following the first-principles linear combination of atomic orbitals method within the framework of a posteriori density-functional theory implemented in the CRYSTAL code. Pressure-induced phase transitions among the four polymorphs α, β, cubic-γ and aAs-γ of Be 3 N 2 are examined. Enthalpy-pressure curves do not show the possibility of pressure-induced structural phase transition to the cubic-γ phase. However, α → aAs-γ and β → aAs-γ structural phase transitions are observed at 139 GPa and 93 GPa, respectively. Band structure calculations predict that aAs-γ Be 3 N 2 is an indirect semiconductor with 4.73 eV bandgap at L point. Variation of bandgap with pressure and deformation potentials are studied for the α, β and aAs-γ polymorphs. Pressure-dependent band structure calculations reveal that, within the low-pressure limit, bandgaps of β and aAs-γ increase with pressure unlike α-Be 3 N 2 .

Quantifying Chaos by Various Computational Methods. Part 2: Vibrations of the Bernoulli–Euler Beam Subjected to Periodic and Colored Noise

Directory of Open Access Journals (Sweden)

Jan Awrejcewicz

2018-03-01

Full Text Available In this part of the paper, the theory of nonlinear dynamics of flexible Euler–Bernoulli beams (the kinematic model of the first-order approximation under transverse harmonic load and colored noise has been proposed. It has been shown that the introduced concept of phase transition allows for further generalization of the problem. The concept has been extended to a so-called noise-induced transition, which is a novel transition type exhibited by nonequilibrium systems embedded in a stochastic fluctuated medium, the properties of which depend on time and are influenced by external noise. Colored noise excitation of a structural system treated as a system with an infinite number of degrees of freedom has been studied.

Pressure induced phase transition in Pb6Bi2S9

DEFF Research Database (Denmark)

Olsen, Lars Arnskov; Friese, Karen; Makovicky, Emil

2011-01-01

consists of two types of moduli with SnS/TlI archetype structure in which the Pb and Bi lone pairs are strongly expressed. The mechanism of the phase transition is described in detail and the results are compared to the closely related phase transition in Pb3Bi2S6 (lillianite).......The crystal structure of Pb6Bi2S9 is investigated at pressures between 0 and 5.6 GPa with X-ray diffraction on single-crystals. The pressure is applied using diamond anvil cells. Heyrovskyite (Bbmm, a = 13.719(4) Å, b = 31.393(9) Å, c = 4.1319(10) Å, Z = 4) is the stable phase of Pb6Bi2S9...... at ambient conditions and is built from distorted moduli of PbS-archetype structure with a low stereochemical activity of the Pb2+ and Bi3+ lone electron pairs. Heyrovskyite is stable until at least 3.9 GPa and a first-order phase transition occurs between 3.9 and 4.8 GPa. A single-crystal is retained after...

Shock-Assisted Superficial Hexagonal-to-Cubic Phase Transition in GaN/Sapphire Interface Induced by Using Ultra-violet Laser Lift-Of Techniques

International Nuclear Information System (INIS)

Wei-Hua, Chen; Xiao-Dong, Hu; Xiang-Ning, Kang; Xu-Rong, Zhou; Xiao-Min, Zhang; Tong-Jun, Yu; Zhi-Jian, Yang; Ke, Xu; Guo-Yi, Zhang; Xu-Dong, Shan; Li-Ping, You

2009-01-01

Ultra-violet (KrF excimer laser, λ = 248 nm) laser lift-of (LLO) techniques have been operated to the GaN/sapphire structure to separate GaN from the sapphire substrate. Hexagonal to cubic phase transformation induced by the ultra-violet laser lift-of (UV-LLO) has been characterized by micro-Raman spectroscopy, micro-photoluminescence, along with high-resolution transmission electron microscopy (HRTEM). HRTEM indicates that UV-LLO induced phase transition takes place above the LLO interface, without phase transition under the LLO interface. The formed cubic GaN often exists as nanocrystal grains attaching on the bulk hexagonal GaN. The half-loop-cluster-like UV-LLO interface indicates that the LLO-induced shock waves has generated and played an assistant role in the decomposition of the hexagonal GaN and in the formation of cubic GaN grains at the LLO surface

Phase Noise Tolerant QPSK Receiver Using Phase Sensitive Wavelength Conversion

DEFF Research Database (Denmark)

Da Ros, Francesco; Xu, Jing; Lei, Lei

2013-01-01

A novel QPSK receiver based on a phase noise reduction pre-stage exploiting PSA in a HNLF and balanced detection is presented. Receiver sensitivity improvement over a conventional balanced receiver is demonstrated.......A novel QPSK receiver based on a phase noise reduction pre-stage exploiting PSA in a HNLF and balanced detection is presented. Receiver sensitivity improvement over a conventional balanced receiver is demonstrated....

Dynamic Test Method Based on Strong Electromagnetic Pulse for Electromagnetic Shielding Materials with Field-Induced Insulator-Conductor Phase Transition

Science.gov (United States)

Wang, Yun; Zhao, Min; Wang, Qingguo

2018-01-01

In order to measure the pulse shielding performance of materials with the characteristic of field-induced insulator-conductor phase transition when materials are used for electromagnetic shielding, a dynamic test method was proposed based on a coaxial fixture. Experiment system was built by square pulse source, coaxial cable, coaxial fixture, attenuator, and oscilloscope and insulating components. S11 parameter of the test system was obtained, which suggested that the working frequency ranges from 300 KHz to 7.36 GHz. Insulating performance is good enough to avoid discharge between conductors when material samples is exposed in the strong electromagnetic pulse field up to 831 kV/m. This method is suitable for materials with annular shape, certain thickness and the characteristic of field-induced insulator-conductor phase transition to get their shielding performances of strong electromagnetic pulse.

Staphylococcus aureus-induced G2/M phase transition delay in host epithelial cells increases bacterial infective efficiency.

Directory of Open Access Journals (Sweden)

Ludmila Alekseeva

Full Text Available Staphylococcus aureus is a highly versatile, opportunistic pathogen and the etiological agent of a wide range of infections in humans and warm-blooded animals. The epithelial surface is its principal site of colonization and infection. In this work, we investigated the cytopathic effect of S. aureus strains from human and animal origins and their ability to affect the host cell cycle in human HeLa and bovine MAC-T epithelial cell lines. S. aureus invasion slowed down cell proliferation and induced a cytopathic effect, resulting in the enlargement of host cells. A dramatic decrease in the number of mitotic cells was observed in the infected cultures. Flow cytometry analysis revealed an S. aureus-induced delay in the G2/M phase transition in synchronous HeLa cells. This delay required the presence of live S. aureus since the addition of the heat-killed bacteria did not alter the cell cycle. The results of Western blot experiments showed that the G2/M transition delay was associated with the accumulation of inactive cyclin-dependent kinase Cdk1, a key inducer of mitosis entry, and with the accumulation of unphosphorylated histone H3, which was correlated with a reduction of the mitotic cell number. Analysis of S. aureus proliferation in asynchronous, G1- and G2-phase-enriched HeLa cells showed that the G2 phase was preferential for bacterial infective efficiency, suggesting that the G2 phase delay may be used by S. aureus for propagation within the host. Taken together, our results divulge the potential of S. aureus in the subversion of key cellular processes such as cell cycle progression, and shed light on the biological significance of S. aureus-induced host cell cycle alteration.

Prevention and Treatment of Noise-Induced Tinnitus

Science.gov (United States)

2014-09-01

Tinnitus PRINCIPAL INVESTIGATOR: Dr. Richard A. Altschuler CONTRACTING ORGANIZATION: University of Michigan REPORT DATE: 2014...3 Ju 2014 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Prevention and Treatment of Noise-Induced Tinnitus 5b. GRANT NUMBER 5c. PROGRAM...prevent or treat noise induced tinnitus . Our studies showed a military relevant small arms fire-like noise will induce tinnitus in approximately 33

Pressure-induced phase transitions in silicon studied by neural network-based metadynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Behler, Joerg [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Lehrstuhl fuer Theoretische Chemie, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Martonak, Roman [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynska dolina F2, 84248 Bratislava (Slovakia); Donadio, Davide [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland); Department of Chemistry, UC Davis, One Shields Ave., Davis, CA 95616 (United States); Parrinello, Michele [Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, Lugano (Switzerland)

2008-12-15

We present a combination of the metadynamics method for the investigation of pressure-induced phase transitions in solids with a neural network representation of high-dimensional density-functional theory (DFT) potential-energy surfaces. In a recent illustration of the method for the complex high-pressure phase diagram of silicon[Behler et al., Phys. Rev. Lett. 100, 185501 (2008)] we have shown that the full sequence of phases can be reconstructed by a series of subsequent simulations. In the present paper we give a detailed account of the underlying methodology and discuss the scope and limitations of the approach, which promises to be a valuable tool for the investigation of a variety of inorganic materials. The method is several orders of magnitude faster than a direct coupling of metadynamics with electronic structure calculations, while the accuracy is essentially maintained, thus providing access to extended simulations of large systems. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Numerical results on noise-induced dynamics in the subthreshold regime for thermoacoustic systems

Science.gov (United States)

Gupta, Vikrant; Saurabh, Aditya; Paschereit, Christian Oliver; Kabiraj, Lipika

2017-03-01

Thermoacoustic instability is a serious issue in practical combustion systems. Such systems are inherently noisy, and hence the influence of noise on the dynamics of thermoacoustic instability is an aspect of practical importance. The present work is motivated by a recent report on the experimental observation of coherence resonance, or noise-induced coherence with a resonance-like dependence on the noise intensity as the system approaches the stability margin, for a prototypical premixed laminar flame combustor (Kabiraj et al., Phys. Rev. E, 4 (2015)). We numerically investigate representative thermoacoustic models for such noise-induced dynamics. Similar to the experiments, we study variation in system dynamics in response to variations in the noise intensity and in a critical control parameter as the systems approach their stability margins. The qualitative match identified between experimental results and observations in the representative models investigated here confirms that coherence resonance is a feature of thermoacoustic systems. We also extend the experimental results, which were limited to the case of subcritical Hopf bifurcation, to the case of supercritical Hopf bifurcation. We identify that the phenomenon has qualitative differences for the systems undergoing transition via subcritical and supercritical Hopf bifurcations. Two important practical implications are associated with the findings. Firstly, the increase in noise-induced coherence as the system approaches the onset of thermoacoustic instability can be considered as a precursor to the instability. Secondly, the dependence of noise-induced dynamics on the bifurcation type can be utilised to distinguish between subcritical and supercritical bifurcation prior to the onset of the instability.

Phase transitions in scale-free neural networks: Departure from the standard mean-field universality class

International Nuclear Information System (INIS)

Aldana, Maximino; Larralde, Hernan

2004-01-01

We investigate the nature of the phase transition from an ordered to a disordered state that occurs in a family of neural network models with noise. These models are closely related to the majority voter model, where a ferromagneticlike interaction between the elements prevails. Each member of the family is distinguished by the network topology, which is determined by the probability distribution of the number of incoming links. We show that for homogeneous random topologies, the phase transition belongs to the standard mean-field universality class, characterized by the order parameter exponent β=1/2. However, for scale-free networks we obtain phase transition exponents ranging from 1/2 to infinity. Furthermore, we show the existence of a phase transition even for values of the scale-free exponent in the interval (1.5,2], where the average network connectivity diverges

First-Order Quantum Phase Transition for Dicke Model Induced by Atom-Atom Interaction

International Nuclear Information System (INIS)

Zhao Xiu-Qin; Liu Ni; Liang Jiu-Qing

2017-01-01

In this article, we use the spin coherent state transformation and the ground state variational method to theoretically calculate the ground function. In order to consider the influence of the atom-atom interaction on the extended Dicke model’s ground state properties, the mean photon number, the scaled atomic population and the average ground energy are displayed. Using the self-consistent field theory to solve the atom-atom interaction, we discover the system undergoes a first-order quantum phase transition from the normal phase to the superradiant phase, but a famous Dicke-type second-order quantum phase transition without the atom-atom interaction. Meanwhile, the atom-atom interaction makes the phase transition point shift to the lower atom-photon collective coupling strength. (paper)

Pressure-induced phase transitions in single-crystalline Cu4Bi4S9 nanoribbons

International Nuclear Information System (INIS)

Hu Jing-Yu; Li Jing; Zhao Qing; Shi Li-Jie; Zou Bing-Suo; Zhang Si-Jia; Zhao Hao-Fei; Zhang Qing-Hua; Yao Yuan; Zhu Ke; Liu Yu-Long; Jin Chang-Qing; Yu Ri-Cheng; Li Yan-Chun; Li Xiao-Dong; Liu Jing

2013-01-01

In situ angle dispersive synchrotron X-ray diffraction and Raman scattering measurements under pressure are employed to study the structural evolution of Cu 4 Bi 4 S 9 nanoribbons, which are fabricated by using a facile solvothermal method. Both experiments show that a structural phase transition occurs near 14.5 GPa, and there is a pressure-induced reversible amorphization at about 25.6 GPa. The electrical transport property of a single Cu 4 Bi 4 S 9 nanoribbon under different pressures is also investigated

Nonequilibrium phase transitions, fluctuations and correlations in an active contractile polar fluid.

Science.gov (United States)

Gowrishankar, Kripa; Rao, Madan

2016-02-21

We study the patterning, fluctuations and correlations of an active polar fluid consisting of contractile polar filaments on a two-dimensional substrate, using a hydrodynamic description. The steady states generically consist of arrays of inward pointing asters and show a continuous transition from a moving lamellar phase, a moving aster street, to a stationary aster lattice with no net polar order. We next study the effect of spatio-temporal athermal noise, parametrized by an active temperature TA, on the stability of the ordered phases. In contrast to its equilibrium counterpart, we find that the active crystal shows true long range order at low TA. On increasing TA, the asters dynamically remodel, concomitantly we find novel phase transitions characterized by bond-orientational and polar order upon "heating".

A minimal model of burst-noise induced bistability.

Directory of Open Access Journals (Sweden)

Johannes Falk

Full Text Available We investigate the influence of intrinsic noise on stable states of a one-dimensional dynamical system that shows in its deterministic version a saddle-node bifurcation between monostable and bistable behaviour. The system is a modified version of the Schlögl model, which is a chemical reaction system with only one type of molecule. The strength of the intrinsic noise is varied without changing the deterministic description by introducing bursts in the autocatalytic production step. We study the transitions between monostable and bistable behavior in this system by evaluating the number of maxima of the stationary probability distribution. We find that changing the size of bursts can destroy and even induce saddle-node bifurcations. This means that a bursty production of molecules can qualitatively change the dynamics of a chemical reaction system even when the deterministic description remains unchanged.

Strain-induced phase transition and electron spin-polarization in graphene spirals.

Science.gov (United States)

Zhang, Xiaoming; Zhao, Mingwen

2014-07-16

Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

Spectral Weighting Functions for Single-symbol Phase-noise Specifications in OFDM Systems

NARCIS (Netherlands)

Hoeksema, F.W.; Schiphorst, Roelof; Slump, Cornelis H.

2003-01-01

For the specification of phase-noise requirements for the front-end of a HiperLAN/2 system we investigated available literature on the subject. Literature differed in several aspects. One aspect is in the type of phase-noise used (Wiener phase-noise or small-angle phase noise). A Wiener phase-noise

Structural phase transitions in niobium oxide nanocrystals

Science.gov (United States)

Yuvakkumar, R.; Hong, Sun Ig

2015-09-01

Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

Martensitic phase transitions

International Nuclear Information System (INIS)

Petry, W.; Neuhaus, J.

1996-01-01

Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs

Martensitic phase transitions

Energy Technology Data Exchange (ETDEWEB)

Petry, W; Neuhaus, J [Techn. Universitaet Muenchen, Physik Department E13, Munich (Germany)

1996-11-01

Many elements transform from a high temperature bcc phase to a more dense packed temperature phase. The great majority of these transitions are of 1st order, displacive and reconstructive. The lattice potentials which govern these martensitic transitions can be probed by inelastic neutron scattering, thereby answering fundamental questions like : Will the transition be announced by dynamical or static fluctuations? What are the trajectories for the displacements needed for the transformation? Does the vibrational entropy stabilize the high temperature phase? Are the unusual transport properties in these materials related to their ability to transform? (author) 17 figs., 1 tab., 46 refs.

Noise Annoyance Produced by Commercial Vehicles Transit on Rumble Strips

Science.gov (United States)

Zaiton, Haron; Khairulzan, Yahya; Nadirah, Darus; Nordiana, Mashros; Azril, Hezmi Muhammad; Samah Rosiah, Abu; Mutalif, Abdul Hameed Abdul; Asyraf, Norudin Wan Mohammad; Habab, Abd Halil Muhammad; Zanariah, Jahya; Hanifi, Othman Mohd

2018-03-01

This paper reports on research examining the extent of noise annoyance affecting residents within the vicinity of installation of two types of transverse rumble strips (TRS), namely Middle Overlapped (MO) and Multilayer Overlapping (MLO). In order to assess the noise annoyance in the area, measurements were taken at 7.5m from centre of road with TRS installation using single vehicle test to determine the extent of changes of sound level indices and sound spectrum. Two light and two medium weight commercial vehicles were used. Indicators LAeq, LAFmax, LAImax, LAIeq, and LASmax were used to determine impulsivity that led to noise annoyance. The results showed that, at 30 km/h, all commercial vehicles considered in this study that transited on MO produced impulsive noise, while only light commercial vehicles caused noise annoyance when they transited on MLO. The research also analysed the extent of low-frequency noise and found a significant low-frequency component, which indicated that noise annoyance might arise from the hitting of MO and MLO by the commercial vehicles. For night-time related annoyance, it was suggested that an additional weighting factor could be added to the average A-weighted value during night-time.

Quantum phase transitions between a class of symmetry protected topological states

Energy Technology Data Exchange (ETDEWEB)

Tsui, Lokman; Jiang, Hong-Chen; Lu, Yuan-Ming; Lee, Dung-Hai

2015-07-01

The subject of this paper is the phase transition between symmetry protected topological states (SPTs). We consider spatial dimension d and symmetry group G so that the cohomology group, Hd+1(G,U(1)), contains at least one Z2n or Z factor. We show that the phase transition between the trivial SPT and the root states that generate the Z2n or Z groups can be induced on the boundary of a (d+1)-dimensional View the MathML source-symmetric SPT by a View the MathML source symmetry breaking field. Moreover we show these boundary phase transitions can be “transplanted” to d dimensions and realized in lattice models as a function of a tuning parameter. The price one pays is for the critical value of the tuning parameter there is an extra non-local (duality-like) symmetry. In the case where the phase transition is continuous, our theory predicts the presence of unusual (sometimes fractionalized) excitations corresponding to delocalized boundary excitations of the non-trivial SPT on one side of the transition. This theory also predicts other phase transition scenarios including first order transition and transition via an intermediate symmetry breaking phase.

Phase transitions in nuclear physics

Energy Technology Data Exchange (ETDEWEB)

Moretto, L.G.; Phair, L.; Wozniak, G.J.

1997-08-01

A critical overview of the low energy phase transitions in nuclei is presented with particular attention to the 2nd (1st) order pairing phase transitions, and to the 1st order liquid-vapor phase transition. The role of fluctuations in washing out these transitions is discussed and illustrated with examples. A robust indicator of phase coexistence in multifragmentation is presented.

Phase transitions in nuclear physics

International Nuclear Information System (INIS)

Moretto, L.G.; Phair, L.; Wozniak, G.J.

1997-08-01

A critical overview of the low energy phase transitions in nuclei is presented with particular attention to the 2nd (1st) order pairing phase transitions, and to the 1st order liquid-vapor phase transition. The role of fluctuations in washing out these transitions is discussed and illustrated with examples. A robust indicator of phase coexistence in multifragmentation is presented

Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation.

Science.gov (United States)

Mohajerin-Ariaei, Amirhossein; Ziyadi, Morteza; Chitgarha, Mohammad Reza; Almaiman, Ahmed; Cao, Yinwen; Shamee, Bishara; Yang, Jeng-Yuan; Akasaka, Youichi; Sekiya, Motoyoshi; Takasaka, Shigehiro; Sugizaki, Ryuichi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

2015-07-15

We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification in the saturation regime. Phase noise reduction of ∼40% and OSNR-gain of ∼3  dB at BER 10(-3) are experimentally demonstrated for 20- and 30-Gbaud QPSK input signals.

Phase control of squeezed state in double electromagnetically induced transparency system with a loop-transition structure

Science.gov (United States)

Li, Yuan; Zhou, Yusheng; Wang, Yong; Ling, Qiang; Chen, Bing; Dou, Yan; Zhang, Wei; Gao, Weiqing; Guo, Zhiqiang; Zhang, Junxiang

2018-03-01

We theoretically study the squeezed probe light passing through a double electromagnetically induced transparency (DEIT) system, in which a microwave field and two coupling lights drive a loop transition. It is shown that the output squeezing can be maintained in both two transparency windows of DEIT, and it can also be manipulated by the relative phase of the three driving fields. The influence of the intensity of applied fields and the optical depth of atoms on the squeezing is also investigated. This study offers possibilities to manipulate the squeezing propagation in atomic media by the phase of electromagnetic fields.

Pressure induced phase transitions in transition metal nitrides: Ab initio study

Energy Technology Data Exchange (ETDEWEB)

Srivastava, Anurag; Chauhan, Mamta [Advanced Material Research Lab, Indian Institute of Information Technology and Management, Gwalior 474010 (India); Singh, R.K. [Department of Physics, ITM University, Gurgaon 122017 (India)

2011-12-15

We have analyzed the stability of transition metal nitrides (TMNs) XN (X = Ti, Zr, Hf, V, Nb, Ta) in their original rocksalt (B1) and hypothetical CsCl (B2) type phases under high compression. The ground state total energy calculation approach of the system has been used through the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) type parameterization as exchange correlation functional. In the whole series of nitrides taken into consideration, tantalum nitride is found to be the most stable. We have observed that under compression the original B1-type phase of these nitrides transforms to a B2-type phase. We have also discussed the computation of ground state properties, like the lattice constant (a), bulk modulus (B{sub 0}) and first order pressure derivative of the bulk modulus (B'{sub 0}) of the TMNs and their host elements. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Thermodynamics of phase transitions

International Nuclear Information System (INIS)

Cofta, H.

1972-01-01

The phenomenology of the phase transitions has been considered. The definitions of thermodynamic functions and parameters, as well as those of the phase transitions, are given and some of the relations between those quantities are discussed. The phase transitions classification proposed by Ehrenfest has been described. The most important features of phase transitions are discussed using the selected physical examples including the critical behaviour of ferromagnetic materials at the Curie temperature and antiferromagnetic materials at the Neel temperature. Some aspects of the Ehrenfest's equations, that have been derived, for the interfacial lines and surfaces are considered as well as the role the notion of interfaces. (S.B.)

Fermion condensation quantum phase transition versus conventional quantum phase transitions

International Nuclear Information System (INIS)

Shaginyan, V.R.; Han, J.G.; Lee, J.

2004-01-01

The main features of fermion condensation quantum phase transition (FCQPT), which are distinctive in several aspects from that of conventional quantum phase transition (CQPT), are considered. We show that in contrast to CQPT, whose physics in quantum critical region is dominated by thermal and quantum fluctuations and characterized by the absence of quasiparticles, the physics of a Fermi system near FCQPT or undergone FCQPT is controlled by the system of quasiparticles resembling the Landau quasiparticles. Contrary to the Landau quasiparticles, the effective mass of these quasiparticles strongly depends on the temperature, magnetic fields, density, etc. This system of quasiparticles having general properties determines the universal behavior of the Fermi system in question. As a result, the universal behavior persists up to relatively high temperatures comparatively to the case when such a behavior is determined by CQPT. We analyze striking recent measurements of specific heat, charge and heat transport used to study the nature of magnetic field-induced QCP in heavy-fermion metal CeCoIn 5 and show that the observed facts are in good agreement with our scenario based on FCQPT and certainly seem to rule out the critical fluctuations related with CQPT. Our general consideration suggests that FCQPT and the emergence of novel quasiparticles near and behind FCQPT and resembling the Landau quasiparticles are distinctive features intrinsic to strongly correlated substances

Theoretical study of B3-to-B1 phase transition in ZnS

International Nuclear Information System (INIS)

Li, Qiang; Zhang, Rui; Lv, Tianquan; Cao, Qilong

2016-01-01

The pressure-induced phase transformation from B3 to B1 structures in ZnS using first-principle projector-augmented wave method is studied. To understand the nature and driving force behind the transition, the interesting properties in both phases, including enthalpy, phonon dispersion curves and elastic constants, are systematically investigated. The results show that the calculated transition pressure is within the range of 16.33 GPa to 19.04 GPa, which is in good agreement with the available experimental and theoretical data. The transition process can be viewed as the appearance and disappearance of very slight lattice distortion accompanied by the movement of Zn and S atoms along the [111] crystallographic axis. The physical driving force of the B3–B1 phase transition is confirmed to be a coupling effect between the mechanical instability of B3 phase under pressure and the softening acoustic phonon mode resulting from the pressure-induced lattice deformation. For B1 phase, it is further predicted that a new phase transition takes place at about 59.9 GPa. - Highlights: • The phase transformation from B3 to B1 structures in ZnS is studied using first-principle method. • The predicted transition pressure is within the range of 16.33 to 19.04 GPa. • The transition process can be viewed as the appearance and disappearance of very slight lattice distortion. • Physical driving force of the transition is a coupling effect between the mechanical instability and softening phonon. • For B1 phase, it is further predicted that a new phase transition takes place at about 59.9 GPa.

Surface charge sensing by altering the phase transition in VO2

Science.gov (United States)

Kumar, S.; Esfandyarpour, R.; Davis, R.; Nishi, Y.

2014-08-01

Detection of surface charges has various applications in medicine, electronics, biotechnology, etc. The source of surface charge induction may range from simple charge-polarized molecules like water to complicated proteins. It was recently discovered that surface charge accumulation can alter the temperature at which VO2 undergoes a Mott transition. Here, we deposited polar molecules onto the surface of two-terminal thin-film VO2 lateral devices and monitored the joule-heating-driven Mott transition, or conductance switching. We observed that the power required to induce the conductance switching reduced upon treatment with polar molecules and, using in-situ blackbody-emission direct measurement of local temperature, we show that this reduction in power was accompanied by reduction in the Mott transition temperature. Further evidence suggested that this effect has specificity to the nature of the species used to induce surface charges. Using x-ray absorption spectroscopy, we also show that there is no detectable change in oxidation state of vanadium or structural phase in the bulk of the 40 nm VO2 thin-film even as the phase transition temperature is reduced by up to 20 K by the polar molecules. The ability to alter the phase transition parameters by depositing polar molecules suggests a potential application in sensing surface charges of different origins and this set of results also highlights interesting aspects of the phase transition in VO2.

The model of metal-insulator phase transition in vanadium oxide

International Nuclear Information System (INIS)

Vikhnin, V.S.; Lysenko, S.; Rua, A.; Fernandez, F.; Liu, H.

2005-01-01

Thermally induced metal-insulator phase transitions (PT) in VO 2 thin films are studied theoretically and experimentally. The hysteresis phenomena in the region of the transition for different type thin films were investigated. The phenomenological model of the PT is suggested. The charge transfer-lattice instability in VO 2 metallic phase is considered as basis of the first order metal-insulator PT in VO 2 . The charge transfer is treated as an order parameter

Phase transitions modern applications

CERN Document Server

Gitterman, Moshe

2014-01-01

This book provides a comprehensive review of the theory of phase transitions and its modern applications, based on the five pillars of the modern theory of phase transitions i.e. the Ising model, mean field, scaling, renormalization group and universality. This expanded second edition includes, along with a description of vortices and high temperature superconductivity, a discussion of phase transitions in chemical reaction and moving systems. The book covers a close connection between phase transitions and small world phenomena as well as scale-free systems such as the stock market and the Internet. Readership: Scientists working in different fields of physics, chemistry, biology and economics as well as teaching material for undergraduate and graduate courses.

Magnetic properties of Gd5(Si1.5Ge2.5) near the temperature and magnetic field induced first order phase transition

International Nuclear Information System (INIS)

Levin, E.M.; Gschneidner, K.A.; Pecharsky, V.K.

2001-01-01

The temperature (from 5 to 300 K) and DC magnetic field (from 0 to 90 kOe) dependencies of the DC magnetization and magnetic susceptibility, and the temperature (from 5 to 350 K) dependency of the AC magnetic susceptibility of Gd 5 (Si 1.5 Ge 2.5 ) have been studied. The temperature and/or magnetic field induced magnetic phase transition in Gd 5 (Si 1.5 Ge 2.5 ) is a first order ferromagnet-paramagnet transition. The temperature of the magnetic transition in low AC magnetic field is 206 and 217 K for cooling and heating, respectively. The DC magnetic field increases the transition temperature by ∼0.36 K/kOe indicating that the paramagnetic phase can be reversibly transformed into the ferromagnetic phase. When the magnetic field is removed, the ferromagnetic phase transforms into the paramagnetic phase showing a large remanence-free hysteresis. The magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed. The magnetic field dependence of the magnetization in the vicinity of the first order phase transition shows evidence for the formation of a magnetically heterogeneous system in the volume of Gd 5 (Si 1.5 Ge 2.5 ) specimen where the magnetically ordered (ferromagnetic) and disordered (paramagnetic) phases co-exist

Electric field-induced phase transitions and composition-driven nanodomains in rhombohedral-tetragonal potassium-sodium niobate-based ceramics

KAUST Repository

Lv, Xiang

2017-08-07

The mechanisms behind the high piezoelectricity of (K,Na)NbO3-based lead-free ceramics were investigated, including electric field-induced phase transitions and composition-driven nanodomains. The construction of a rhombohedral-tetragonal (R-T) phase boundary, confirmed using several advanced techniques, allowed a large piezoelectric constant (d33) of 450 ± 5 pC/N to be obtained in (1-x)K0.4Na0.6Nb0.945Sb0.055O3-xBi0.5Na0.5(Hf1-ySny)O3 (0 ≤ x ≤ 0.06 and 0 ≤ y ≤ 0.5) ceramics possessing an ultralow ΔUT-R of 7.4 meV. More importantly, the existence of an intermediate phase, i.e., the electric-induced phase (EIP), bridging the rhombohedral R [Ps//(111)] and tetragonal T [Ps//(001)] phases during the polarization rotation was demonstrated. Striped nanodomains (∼40 nm) that easily responded to external stimulation were also observed in the ceramics with an R-T phase. Thus, the enhanced piezoelectric properties originated from EIP and the striped nanodomains.

Low-pH-Induced Lamellar to Bicontinuous Primitive Cubic Phase Transition in Dioleoylphosphatidylserine/Monoolein Membranes.

Science.gov (United States)

Oka, Toshihiko; Hasan, Moynul; Islam, Md Zahidul; Moniruzzaman, Md; Yamazaki, Masahito

2017-10-31

Electrostatic interactions (EIs) play important roles in the structure and stability of inverse bicontinuous cubic (Q II ) phases of lipid membranes. We examined the effect of pH on the phase of dioleoylphosphatidylserine (DOPS)/monoolein (MO) membranes at low ionic strengths using small-angle X-ray scattering (SAXS). We found that the phase transitions from lamellar liquid-crystalline (L α ) to primitive cubic (Q II P ) phases in DOPS/MO (2/8 molar ratio) membranes occurred in buffers containing 50 mM NaCl at and below the final pH of 2.75 as the pH of the membrane suspension was decreased from a neutral value. The kinetic pathway of this transition was revealed using time-resolved SAXS with a stopped-flow apparatus. The first step is a rapid transition from the L α phase to the hexagonal II (H II ) phase, and the second step is a slow transition from the H II phase to the Q II P phase. We determined the rate constants of the first step, k 1 , and of the second step, k 2 , by analyzing the time course of SAXS intensities quantitatively. The k 1 value increased with temperature. The analysis of this result provided the values of its apparent activation energy, which were constant over temperature but increased with pH. This can be explained by an EI effect on the free energy of the transition state. In contrast, the k 2 value decreased with temperature, indicating that the true activation energy increased with temperature. These experimental results were analyzed using the theory of the activation energy of phase transitions of lipid membranes when the free energy of the transition state depends on temperature. On the basis of these results, we discussed the mechanism of this phase transition.

Electronic properties and phase transitions in low-dimensional semiconductors

International Nuclear Information System (INIS)

Panich, A M

2008-01-01

We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX 2 (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, nonlinear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX 2 compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. The electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed. (topical review)

Phase transitions in surfactant monolayers

International Nuclear Information System (INIS)

Casson, B.D.

1998-01-01

Two-dimensional phase transitions have been studied in surfactant monolayers at the air/water interface by sum-frequency spectroscopy and ellipsometry. In equilibrium monolayers of medium-chain alcohols C n H 2n+1 OH (n = 9-14) a transition from a two-dimensional crystalline phase to a liquid was observed at temperatures above the bulk melting point. The small population of gauche defects in the solid phase increased only slightly at the phase transition. A model of the hydrocarbon chains as freely rotating rigid rods allowed the area per molecule and chain tilt in the liquid phase to be determined. The area per molecule, chain tilt and density of the liquid phase all increased with increasing chain length, but for each chain length the density was higher than in a bulk liquid hydrocarbon. In a monolayer of decanol adsorbed at the air/water interface a transition from a two-dimensional liquid to a gas was observed. A clear discontinuity in the coefficient of ellipticity as a function of temperature showed that the transition is first-order. This result suggests that liquid-gas phase transitions in surfactant monolayers may be more widespread than once thought. A solid-liquid phase transition has also been studied in mixed monolayers of dodecanol with an anionic surfactant (sodium dodecyl sulphate) and with a homologous series of cationic surfactants (alkyltrimethylammonium bromides: C n TABs, n = 12, 14, 16). The composition and structure of the mixed monolayers was studied above and below the phase transition. At low temperatures the mixed monolayers were as densely packed as a monolayer of pure dodecanol in its solid phase. At a fixed temperature the monolayers under-went a first-order phase transition to form a phase that was less dense and more conformationally disordered. The proportion of ionic surfactant in the mixed monolayer was greatest in the high temperature phase. As the chain length of the C n TAB increased the number of conformational defects

Phase transition of the FCC Ising ferromagnet with competing interactions

International Nuclear Information System (INIS)

Oh, J.H.; Lee, J.Y.; Kim, D.C.

1984-01-01

A molecular field theory with correlation and Monte Carlo simulations are utilized to determine the zero field phase diagram of a fcc Ising model with ferromagnetic nearest neighbor(-J) and antiferromagnetic next neighbor (*aJ) interactions. The correlated molecular field theory predicts a fluctuation induced first order phase transition for 0.87<*a<1.31. Monte Carlo analysis indicates that the first order transition occurs for a somewhat wider range of *a. The transition temperatures obtained by the two methods are in good agreement especially near *a=1 where the fluctuation effect is expected to be large. (Author)

Induced Noise Control

National Research Council Canada - National Science Library

Maidanik, G

2002-01-01

The induced noise control parameter is defined in terms of the ratio of the stored energy in a master dynamic system, when it is coupled to an adjunct dynamic system, to that stored energy when the coupling is absent...

Performance analysis of an all-optical OFDM system in presence of non-linear phase noise.

Science.gov (United States)

Hmood, Jassim K; Harun, Sulaiman W; Emami, Siamak D; Khodaei, Amin; Noordin, Kamarul A; Ahmad, Harith; Shalaby, Hossam M H

2015-02-23

The potential for higher spectral efficiency has increased the interest in all-optical orthogonal frequency division multiplexing (OFDM) systems. However, the sensitivity of all-optical OFDM to fiber non-linearity, which causes nonlinear phase noise, is still a major concern. In this paper, an analytical model for estimating the phase noise due to self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) in an all-optical OFDM system is presented. The phase noise versus power, distance, and number of subcarriers is evaluated by implementing the mathematical model using Matlab. In order to verify the results, an all-optical OFDM system, that uses coupler-based inverse fast Fourier transform/fast Fourier transform without any nonlinear compensation, is demonstrated by numerical simulation. The system employs 29 subcarriers; each subcarrier is modulated by a 4-QAM or 16-QAM format with a symbol rate of 25 Gsymbol/s. The results indicate that the phase variance due to FWM is dominant over those induced by either SPM or XPM. It is also shown that the minimum phase noise occurs at -3 dBm and -1 dBm for 4-QAM and 16-QAM, respectively. Finally, the error vector magnitude (EVM) versus subcarrier power and symbol rate is quantified using both simulation and the analytical model. It turns out that both EVM results are in good agreement with each other.

Clustering of noise-induced oscillations

DEFF Research Database (Denmark)

Sosnovtseva, Olga; Fomin, A I; Postnov, D E

2001-01-01

The subject of our study is clustering in a population of excitable systems driven by Gaussian white noise and with randomly distributed coupling strength. The cluster state is frequency-locked state in which all functional units run at the same noise-induced frequency. Cooperative dynamics...

Li-ion batteries: Phase transition

International Nuclear Information System (INIS)

Hou Peiyu; Zhang Yantao; Zhang Lianqi; Chu Geng; Gao Jian

2016-01-01

Progress in the research on phase transitions during Li + extraction/insertion processes in typical battery materials is summarized as examples to illustrate the significance of understanding phase transition phenomena in Li-ion batteries. Physical phenomena such as phase transitions (and resultant phase diagrams) are often observed in Li-ion battery research and already play an important role in promoting Li-ion battery technology. For example, the phase transitions during Li + insertion/extraction are highly relevant to the thermodynamics and kinetics of Li-ion batteries, and even physical characteristics such as specific energy, power density, volume variation, and safety-related properties. (topical review)

Symmetry and Phase Transitions in Nuclei

International Nuclear Information System (INIS)

Iachello, F.

2009-01-01

Phase transitions in nuclei have received considerable attention in recent years, especially after the discovery that, contrary to expectations, systems at the critical point of a phase transition display a simple structure. In this talk, quantum phase transitions (QPT), i.e. phase transitions that occur as a function of a coupling constant that appears in the quantum Hamiltonian, H, describing the system, will be reviewed and experimental evidence for their occurrence in nuclei will be presented. The phase transitions discussed in the talk will be shape phase transitions. Different shapes have different symmetries, classified by the dynamic symmetries of the Interacting Boson Model, U(5), SU(3) and SO(6). Very recently, the concept of Quantum Phase Transitions has been extended to Excited State Quantum Phase Transitions (ESQPT). This extension will be discussed and some evidence for incipient ESQPT in nuclei will be presented. Systems at the critical point of a phase transition are called 'critical systems'. Approximate analytic formulas for energy spectra and other properties of 'critical nuclei', in particular for nuclei at the critical point of the second order U(5)-SO(6) transition, called E(5), and along the line of first order U(5)-SU(3) transitions, called X(5), will be presented. Experimental evidence for 'critical nuclei' will be also shown. Finally, the microscopic derivation of shape phase transitions in nuclei within the framework of density functional methods will be briefly discussed.(author)

Electrostatic Effects in Phase Transitions of Biomembranes between Cubic Phases and Lamellar Liquid-Crystalline (Lα) phase

Science.gov (United States)

Masum, Shah Md.; Li, Shu Jie; Tamba, Yukihiro; Yamashita, Yuko; Yamazaki, Masahito

2004-04-01

Elucidation of the mechanisms of transitions between cubic phase and liquid-crystalline (Lα) phase, and between different IPMS cubic phases, are essential for understanding of dynamics of biomembranes and topological transformation of lipid membranes. Recently, we found that electrostatic interactions due to surface charges of lipid membranes induce transition between cubic phase and Lα phase, and between different IPMS cubic phases. As electrostatic interactions increase, the most stable phase of a monoolein (MO) membrane changes: Q224 ⇒ Q229 ⇒ Lα. We also found that a de novo designed peptide partitioning into electrically neutral lipid membrane changed the phase stability of the MO membranes. As peptide-1 concentration increased, the most stable phase of a MO membrane changes: Q224 ⇒ Q229 ⇒Lα. In both cases, the increase in the electrostatic repulsive interaction greatly reduced the absolute value of spontaneous curvature of the MO monolayer membrane. We also investigated factors such as poly (L-lysine) and osmotic stress to control structure and phase stability of DOPA/MO membranes. Based on these results, we discuss the mechanism of the effect of electrostatic interactions on the stability of cubic phase.

Composition-induced structural phase transitions in the (Ba1-xLax)2In2O5+x (0=

International Nuclear Information System (INIS)

Tenailleau, C.; Pring, A.; Moussa, S.M.; Liu, Y.; Withers, R.L.; Tarantino, S.; Zhang, M.; Carpenter, M.A.

2005-01-01

Composition-induced structural phase changes across the high temperature, fast oxide ion conducting (Ba 1-x La x ) 2 In 2 O 5+x , 0= orthorhombic transition, while the cubic->tetragonal transition could be continuous. Differences between the variation with composition of spectral parameters and of macroscopic strain parameters are consistent with a substantial order/disorder component for the transitions. There is also evidence for precursor effects within the cubic structure before symmetry is broken

Non-equilibrium phase transitions

CERN Document Server

Henkel, Malte; Lübeck, Sven

2009-01-01

This book describes two main classes of non-equilibrium phase-transitions: (a) static and dynamics of transitions into an absorbing state, and (b) dynamical scaling in far-from-equilibrium relaxation behaviour and ageing. The first volume begins with an introductory chapter which recalls the main concepts of phase-transitions, set for the convenience of the reader in an equilibrium context. The extension to non-equilibrium systems is made by using directed percolation as the main paradigm of absorbing phase transitions and in view of the richness of the known results an entire chapter is devoted to it, including a discussion of recent experimental results. Scaling theories and a large set of both numerical and analytical methods for the study of non-equilibrium phase transitions are thoroughly discussed. The techniques used for directed percolation are then extended to other universality classes and many important results on model parameters are provided for easy reference.

Structural phase transitions in BaMo6S8: Evidence for an incommensurate phase

International Nuclear Information System (INIS)

Jorgensen, J.D.; Hinks, D.G.; Hatch, D.M.; Putnam, R.M.

1986-01-01

The structure of BaMo 6 S 8 has been studied over the temperature range 19 K to 573 K by time-of-flight neutron powder diffraction. Below 175 K the data can be suitably refined in a triclinic, P1, cell with volume equal to the rhombohedral, R3, cell common to most Chevrel-phase structures. At temperatures immediately above 175 K, the rhombohedral, R3, Bragg peaks are broadened by satellite reflections which appear to be identical to those recently observed at low temperature in PbMo 6 S 8 and SnMo 6 S 8 . An abrupt change in the sign of the temperature dependence of the hexagonal c axis (∂c/∂T) signals the transition to an undistorted rhombohedral, R3, structure at temperatures above about 350 K. An extended Landau theory determines both continuous and discontinuous transitions from R3 induced by a single order parameter. Analysis of the order parameters inducing commensurate transitions imposes symmetry restrictions on the atomic displacements in the lower symmetry phases. The assumption of an R3 commensurate phase is not consistent with the bond lengths obtained for the distortions to the P1 (or P1) phase for any of the possible cells preserving order parameters. Thus the phase immediately above 175 K cannot be a commensurate R3 structure. This is consistent with experimental evidence. 25 refs., 11 figs., 8 tabs

Noise-induced chaos in a quadratically nonlinear oscillator

International Nuclear Information System (INIS)

Gan Chunbiao

2006-01-01

The present paper focuses on the noise-induced chaos in a quadratically nonlinear oscillator. Simple zero points of the stochastic Melnikov integral theoretically mean the necessary rising of noise-induced chaotic response in the system based on the stochastic Melnikov method. To quantify the noise-induced chaos, the boundary of the system's safe basin is firstly studied and it is shown to be incursively fractal when chaos arises. Three cases are considered in simulating the safe basin of the system, i.e., the system is excited only by the harmonic excitation, by both the harmonic and the Gaussian white noise excitations, and only by the Gaussian white noise excitation. Secondly, the leading Lyapunov exponent by Rosenstein's algorithm is shown to quantify the chaotic nature of the sample time series of the system. The results show that the boundary of the safe basin can also be fractal even if the system is excited only by the external Gaussian white noise. Most importantly, the almost-harmonic, the noise-induced chaotic and the thoroughly random responses can be found in the system

Windows open for highly tunable magnetostructural phase transitions

KAUST Repository

Li, Y.; Wei, Z. Y.; Zhang, H. G.; Liu, E. K.; Luo, H. Z.; Liu, G. D.; Xi, X. K.; Wang, S. G.; Wang, W. H.; Yue, M.; Wu, G. H.; Zhang, Xixiang

2016-01-01

established in the Mn1− yCoyNiGe1− xSix system. Throughout the CTWs, the magnetic-field-induced metamagnetic behavior and giant magnetocaloric effects are obtained. The (Mn,Co)Ni(Ge,Si) system shows great potential as multifunctional phase-transition materials

Phase noise in RF and microwave amplifiers.

Science.gov (United States)

Boudot, Rodolphe; Rubiola, Enrico

2012-12-01

Understanding amplifier phase noise is a critical issue in many fields of engineering and physics, such as oscillators, frequency synthesis, telecommunication, radar, and spectroscopy; in the emerging domain of microwave photonics; and in exotic fields, such as radio astronomy, particle accelerators, etc. Focusing on the two main types of base noise in amplifiers, white and flicker, the power spectral density of the random phase φ(t) is Sφ(f) = b(0) + b(-1)/f. White phase noise results from adding white noise to the RF spectrum in the carrier region. For a given RF noise level, b(0) is proportional to the reciprocal of the carrier power P(0). By contrast, flicker results from a near-dc 1/f noise-present in all electronic devices-which modulates the carrier through some parametric effect in the semiconductor. Thus, b(-1) is a parameter of the amplifier, constant in a wide range of P(0). The consequences are the following: Connecting m equal amplifiers in parallel, b(-1) is 1/m times that of one device. Cascading m equal amplifiers, b(-1) is m times that of one amplifier. Recirculating the signal in an amplifier so that the gain increases by a power of m (a factor of m in decibels) as a result of positive feedback (regeneration), we find that b(-1) is m(2) times that of the amplifier alone. The feedforward amplifier exhibits extremely low b(-1) because the carrier is ideally nulled at the input of its internal error amplifier. Starting with an extensive review of the literature, this article introduces a system-oriented model which describes the phase flickering. Several amplifier architectures (cascaded, parallel, etc.) are analyzed systematically, deriving the phase noise from the general model. There follow numerous measurements of amplifiers using different technologies, including some old samples, and in a wide frequency range (HF to microwaves), which validate the theory. In turn, theory and results provide design guidelines and give suggestions for CAD and

Doping Induced Transition from an Antiferro-Type Order to Phase Separation

International Nuclear Information System (INIS)

Lemanski, R.; Gajek, Z.

2003-01-01

A sequence of transitions from an antiferro-type order to a phase separate state under doping away from half filling is studied within the 1D Falicov-Kimball model. Using the method of restricted phase diagrams the system is analyzed exactly in the thermodynamic limit. Various kinds of ordering, including periodic n-molecular phases and their mixtures are found for a set of values of the interaction constant U. (author)

Phase noise cancellation in polarisation-maintaining fibre links

Science.gov (United States)

Rauf, B.; Vélez López, M. C.; Thoumany, P.; Pizzocaro, M.; Calonico, D.

2018-03-01

The distribution of ultra-narrow linewidth laser radiation is an integral part of many challenging metrological applications. Changes in the optical pathlength induced by environmental disturbances compromise the stability and accuracy of optical fibre networks distributing the laser light and call for active phase noise cancellation. Here we present a laboratory scale optical (at 578 nm) fibre network featuring all polarisation maintaining fibres in a setup with low optical powers available and tracking voltage-controlled oscillators implemented. The stability and accuracy of this system reach performance levels below 1 × 10-19 after 10 000 s of averaging.

Phase transition in finite systems

International Nuclear Information System (INIS)

Chomaz, Ph.; Duflot, V.; Duflot, V.; Gulminelli, F.

2000-01-01

In this paper we present a review of selected aspects of Phase transitions in finite systems applied in particular to the liquid-gas phase transition in nuclei. We show that the problem of the non existence of boundary conditions can be solved by introducing a statistical ensemble with an averaged constrained volume. In such an ensemble the microcanonical heat capacity becomes negative in the transition region. We show that the caloric curve explicitly depends on the considered transformation of the volume with the excitation energy and so does not bear direct informations on the characteristics of the phase transition. Conversely, partial energy fluctuations are demonstrated to be a direct measure of the equation of state. Since the heat capacity has a negative branch in the phase transition region, the presence of abnormally large kinetic energy fluctuations is a signal of the liquid gas phase transition. (author)

Activation barrier scaling and crossover for noise-induced switching in micromechanical parametric oscillators.

Science.gov (United States)

Chan, H B; Stambaugh, C

2007-08-10

We explore fluctuation-induced switching in parametrically driven micromechanical torsional oscillators. The oscillators possess one, two, or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence on frequency detuning with critical exponents that are in agreement with predicted universal scaling relationships. At large detuning, we observe a crossover to a different power law dependence with an exponent that is device specific.

A study of riders' noise exposure on Bay Area Rapid Transit trains.

Science.gov (United States)

Dinno, Alexis; Powell, Cynthia; King, Margaret Mary

2011-02-01

Excessive noise exposure may present a hazard to hearing, cardiovascular, and psychosomatic health. Mass transit systems, such as the Bay Area Rapid Transit (BART) system, are potential sources of excessive noise. The purpose of this study was to characterize transit noise and riders' exposure to noise on the BART system using three dosimetry metrics. We made 268 dosimetry measurements on a convenience sample of 51 line segments. Dosimetry measures were modeled using linear and nonlinear multiple regression as functions of average velocity, tunnel enclosure, flooring, and wet weather conditions and presented visually on a map of the BART system. This study provides evidence of levels of hazardous levels of noise exposure in all three dosimetry metrics. L(eq) and L(max) measures indicate exposures well above ranges associated with increased cardiovascular and psychosomatic health risks in the published literature. L(peak) indicate acute exposures hazardous to adult hearing on about 1% of line segment rides and acute exposures hazardous to child hearing on about 2% of such rides. The noise to which passengers are exposed may be due to train-specific conditions (velocity and flooring), but also to rail conditions (velocity and tunnels). These findings may point at possible remediation (revised speed limits on longer segments and those segments enclosed by tunnels). The findings also suggest that specific rail segments could be improved for noise.

Percolation model of excess electrical noise in transition-edge sensors

International Nuclear Information System (INIS)

Lindeman, M.A.; Anderson, M.B.; Bandler, S.R.; Bilgri, N.; Chervenak, J.; Gwynne Crowder, S.; Fallows, S.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C.A.; Lai, T.; Man, J.; McCammon, D.; Nelms, K.L.; Porter, F.S.; Rocks, L.E.; Saab, T.; Sadleir, J.; Vidugiris, G.

2006-01-01

We present a geometrical model to describe excess electrical noise in transition-edge sensors (TESs). In this model, a network of fluctuating resistors represents the complex dynamics inside a TES. The fluctuations can cause several resistors in series to become superconducting. Such events short out part of the TES and generate noise because much of the current percolates through low resistance paths. The model predicts that excess white noise increases with decreasing TES bias resistance (R/R N ) and that perpendicular zebra stripes reduce noise and alpha of the TES by reducing percolation

Constitutive model for a stress- and thermal-induced phase transition in a shape memory polymer

International Nuclear Information System (INIS)

Guo, Xiaogang; Liu, Liwu; Liu, Yanju; Zhou, Bo; Leng, Jinsong

2014-01-01

Recently, increasing applications of shape memory polymers have pushed forward the development of appropriate constitutive models for smart materials such as the shape memory polymer. During the heating process, the phase transition, which is a continuous time-dependent process, happens in the shape memory polymer, and various individual phases will form at different configuration temperatures. In addition, these phases can generally be divided into two parts: the frozen and active phase (Liu Y et al 2006 Int. J. Plast. 22 279–313). During the heating or cooling process, the strain will be stored or released with the occurring phase transition between these two parts. Therefore, a shape memory effect emerges. In this paper, a new type of model was developed to characterize the variation of the volume fraction in a shape memory polymer during the phase transition. In addition to the temperature variation, the applied stress was also taken as a significant influence factor on the phase transition. Based on the experimental results, an exponential equation was proposed to describe the relationship between the stress and phase transition temperature. For the sake of describing the mechanical behaviors of the shape memory polymer, a three-dimensional constitutive model was established. Also, the storage strain, which was the key factor of the shape memory effect, was also discussed in detail. Similar to previous works, we first explored the effect of applied stress on storage strain. Through comparisons with the DMA and the creep experimental results, the rationality and accuracy of the new phase transition and constitutive model were finally verified. (paper)

Noise-Induced Riddling in Chaotic Systems

International Nuclear Information System (INIS)

Lai, Y.; Grebogi, C.

1996-01-01

Recent works have considered the situation of riddling where, when a chaotic attractor lying in an invariant subspace is transversely stable, the basin of the attractor can be riddled with holes that belong to the basin of another attractor. We show that riddling can be induced by arbitrarily small random noise even if the attractor is transversely unstable, and we obtain universal scaling laws for noise-induced riddling. Our results imply that the phenomenon of riddling can be more prevalent than expected before, as noise is practically inevitable in dynamical systems. copyright 1996 The American Physical Society

Direct investigations of deformation and yield induced structure transitions in polyamide 6 below glass transition temperature with WAXS and SAXS

DEFF Research Database (Denmark)

Guo, Huilong; Wang, Jiayi; Zhou, Chengbo

2015-01-01

Deformation and yield induced structure transitions of polyamide 6 (PA6) were detected with the combination of the wide- and small-angle X-ray scattering (WAXS and SAXS) at 30 degrees C below glass transition temperature (T-g) of PA6. During deformation, gamma-alpha phase transition was found...... at elastic stage. The concentrated stress in crystals at elastic stage provided adequate energy for the direct gamma-alpha phase transition under T-g. The force to promote the gamma-phase into a phase directly is insufficient at the yield stage and a transient phase as a compromise was formed. The transient...... phase was confirmed by DSC measurements and assisted the gamma-alpha phase transition indirectly. The gamma-phase slips into incomplete fragments at yield point, and the parts along tensile direction are responsible for the formation of transient phase. The gamma-fragments after yield is oriented...

Magnetic phase transitions in Er7Rh3 studied on single crystals

International Nuclear Information System (INIS)

Tsutaoka, Takanori; Obata, Keisuke; Cheyvuth, Seng; Koyama, Keiichi

2014-01-01

Highlights: • Magnetic and electrical properties of Er 7 Rh 3 were studied on single crystals. • The magnetic phase diagram along the c-axis was constructed. • The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors. • The anomalies of electrical resistivity can also be described by the magnetic structure in Er 7 Rh 3 . - Abstract: Magnetic phase transitions in Er 7 Rh 3 with the Th 7 Fe 3 type hexagonal structure have been studied on single crystals by measuring magnetization, magnetic susceptibility and electrical resistivity. Er 7 Rh 3 possesses antiferromagnetic state below T N = 13 K. In the ordered state, the two successive magnetic transitions at T t1 = 6.2 K and T t2 = 4.5 K were observed. Several field-induced magnetic transitions were also observed along the a- and c-axes below T N ; magnetic field H – temperature T phase diagram along the c-axis was constructed. The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors which were derived by the previous neutron diffraction studies. Electrical resistivity shows humps just below the magnetic transition temperatures, T N and T t1 due to the super-zone gap formation at the Fermi level; these anomalies can also be described by the magnetic structure changes in Er 7 Rh 3

High phase noise tolerant pilot-tone-aided DP-QPSK optical communication systems

DEFF Research Database (Denmark)

Zhang, Xu; Pang, Xiaodan; Deng, Lei

2012-01-01

In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs) with approx......In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs...

Water-induced ethanol dewetting transition.

Science.gov (United States)

Ren, Xiuping; Zhou, Bo; Wang, Chunlei

2012-07-14

The dewetting transitions of two hydrophobic plates immersed in pure water, aqueous ethanol solutions with concentrations from 25% to 90%, and pure ethanol were investigated by molecular dynamics simulations, where the dewetting transition was analogous to a first-order phase transition from liquid to vapor. It was found that the dewetting transitions occurred except that in the pure ethanol system. Although the ethanol molecules prefer to locate in the vicinity of the two plates, the inter-plate region is unfavorable for water molecules, due to losing more than one hydrogen bond. Moreover, each inter-plate water molecule forms hydrogen bonds on average with about two ethanol molecules. These intermolecular hydrogen bonds cause water and ethanol to cooperatively fill or exit the inter-plate region. Thus, water molecules play a more important role in the inter-plate filling/empty process, and induce the ethanol dewetting transition. Our results provide insight into the effect of water on the ethanol dewetting phenomena.

PHASE NOISE COMPARISON OF SHORT PULSE LASER SYSTEMS

Energy Technology Data Exchange (ETDEWEB)

Shukui Zhang; Stephen Benson; John Hansknecht; David Hardy; George Neil; Michelle D. Shinn

2006-08-27

This paper describes phase noise measurements of several different laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on state-of-the-art short pulse lasers, especially drive lasers for photocathode injectors. Phase noise comparison of the FEL drive laser, electron beam and FEL laser output also will be presented.

Pressure-driven phase transitions in TiOCl and the family (Ca, Sr, Ba)Fe2As2

International Nuclear Information System (INIS)

Zhang YuZhong; Opahle, Ingo; Jeschke, Harald O; ValentI, Roser

2010-01-01

Motivated by recent experimental measurements on pressure-driven phase transitions in Mott insulators as well as the new iron pnictide superconductors, we show that first principles Car-Parrinello molecular dynamics calculations are a powerful method to describe the microscopic origin of such transitions. We present results for (i) the pressure-induced insulator to metal phase transition in the prototypical Mott insulator TiOCl as well as (ii) the pressure-induced structural and magnetic phase transitions in the family of correlated metals AFe 2 As 2 (A = Ca, Sr, Ba). Comparison of our predictions with existing experimental results yields very good agreement.

Theory of structural phase transition in MgTi{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Talanov, V. M., E-mail: valtalanov@mail.ru [South Russian State Polytechnical University (Russian Federation); Shirokov, V. B. [Russian Academy of Sciences, South Science Centre (Russian Federation); Ivanov, V. V. [South Russian State Polytechnical University (Russian Federation); Talanov, M. V. [South Federal University (Russian Federation)

2015-01-15

A theory of phase transition in MgTi{sub 2}O{sub 4} is proposed based on a study of the order-parameter symmetry, thermodynamics, and mechanisms of formation of the atomic and orbital structure of the low-symmetry MgTi{sub 2}O{sub 4} phase. The critical order parameter (which induces a phase transition) is determined. It is shown that the calculated MgTi{sub 2}O{sub 4} tetragonal structure is a result of displacements of magnesium, titanium, and oxygen atoms; ordering of oxygen atoms; and the participation of d{sub xy}, d{sub xz}, and d{sub yz} orbitals. The contribution of noncritical representations to ion displacements is proven to be insignificant. The existence of various metal clusters in the tetragonal phase has been established by calculation in correspondence with experimental data. It is shown (within the Landau theory of phase transitions) that phase states can be changed as a result of both first- and second-order phase transitions: the high-symmetry phase borders two low-symmetry phases by second-order transition lines, while the border between low-symmetry phases is a first-order transition line.

The nuclear liquid gas phase transition and phase coexistence

International Nuclear Information System (INIS)

Chomaz, Ph.

2001-01-01

In this talk we will review the different signals of liquid gas phase transition in nuclei. From the theoretical side we will first discuss the foundations of the concept of equilibrium, phase transition and critical behaviors in infinite and finite systems. From the experimental point of view we will first recall the evidences for some strong modification of the behavior of hot nuclei. Then we will review quantitative detailed analysis aiming to evidence phase transition, to define its order and phase diagram. Finally, we will present a critical discussion of the present status of phase transitions in nuclei and we will draw some lines for future development of this field. (author)

The nuclear liquid gas phase transition and phase coexistence

Energy Technology Data Exchange (ETDEWEB)

Chomaz, Ph

2001-07-01

In this talk we will review the different signals of liquid gas phase transition in nuclei. From the theoretical side we will first discuss the foundations of the concept of equilibrium, phase transition and critical behaviors in infinite and finite systems. From the experimental point of view we will first recall the evidences for some strong modification of the behavior of hot nuclei. Then we will review quantitative detailed analysis aiming to evidence phase transition, to define its order and phase diagram. Finally, we will present a critical discussion of the present status of phase transitions in nuclei and we will draw some lines for future development of this field. (author)

NMR and DSC study of temperature-induced phase transition in aqueous solutions of poly(N-isopropylmethacrylamide-co-acrylamide) copolymers

Czech Academy of Sciences Publication Activity Database

Šťastná, J.; Hanyková, L.; Spěváček, Jiří

2012-01-01

Roč. 290, č. 17 (2012), s. 1811-1817 ISSN 0303-402X R&D Projects: GA ČR GA202/09/1281 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : temperature induced phase transition * thermosensitive copolymer * poly(N-isopropylmethacrylamide-co-acrylamide) Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.161, year: 2012

Ultra-low-noise transition edge sensors for the SAFARI L-band on SPICA

Science.gov (United States)

Goldie, D. J.; Gao, J. R.; Glowacka, D. M.; Griffin, D. K.; Hijmering, R.; Khosropanah, P.; Jackson, B. D.; Mauskopf, P. D.; Morozov, D.; Murphy, J. A.; Ridder, M.; Trappe, N.; O'Sullivan, C.; Withington, S.

2012-09-01

The Far-Infrared Fourier transform spectrometer instrument SAFARI-SPICA which will operate with cooled optics in a low-background space environment requires ultra-sensitive detector arrays with high optical coupling efficiencies over extremely wide bandwidths. In earlier papers we described the design, fabrication and performance of ultra-low-noise Transition Edge Sensors (TESs) operated close to 100mk having dark Noise Equivalent Powers (NEPs) of order 4 × 10-19W/√Hz close to the phonon noise limit and an improvement of two orders of magnitude over TESs for ground-based applications. Here we describe the design, fabrication and testing of 388-element arrays of MoAu TESs integrated with far-infrared absorbers and optical coupling structures in a geometry appropriate for the SAFARI L-band (110 - 210 μm). The measured performance shows intrinsic response time τ ~ 11ms and saturation powers of order 10 fW, and a dark noise equivalent powers of order 7 × 10-19W/√Hz. The 100 × 100μm2 MoAu TESs have transition temperatures of order 110mK and are coupled to 320×320μm2 thin-film β-phase Ta absorbers to provide impedance matching to the incoming fields. We describe results of dark tests (i.e without optical power) to determine intrinsic pixel characteristics and their uniformity, and measurements of the optical performance of representative pixels operated with flat back-shorts coupled to pyramidal horn arrays. The measured and modeled optical efficiency is dominated by the 95Ω sheet resistance of the Ta absorbers, indicating a clear route to achieve the required performance in these ultra-sensitive detectors.

Multipurpose exciter with low phase noise

Science.gov (United States)

Conroy, B.; Le, D.

1989-01-01

Results of an effort to develop a lower-cost exciter with high stability, low phase noise, and controllable phase and frequency for use in Deep Space Network and Goldstone Solar System Radar applications are discussed. Included is a discussion of the basic concept, test results, plans, and concerns.

Plasticity-induced characteristic changes of pattern dynamics and the related phase transitions in small-world neuronal networks

International Nuclear Information System (INIS)

Huang Xu-Hui; Hu Gang

2014-01-01

Phase transitions widely exist in nature and occur when some control parameters are changed. In neural systems, their macroscopic states are represented by the activity states of neuron populations, and phase transitions between different activity states are closely related to corresponding functions in the brain. In particular, phase transitions to some rhythmic synchronous firing states play significant roles on diverse brain functions and disfunctions, such as encoding rhythmical external stimuli, epileptic seizure, etc. However, in previous studies, phase transitions in neuronal networks are almost driven by network parameters (e.g., external stimuli), and there has been no investigation about the transitions between typical activity states of neuronal networks in a self-organized way by applying plastic connection weights. In this paper, we discuss phase transitions in electrically coupled and lattice-based small-world neuronal networks (LBSW networks) under spike-timing-dependent plasticity (STDP). By applying STDP on all electrical synapses, various known and novel phase transitions could emerge in LBSW networks, particularly, the phenomenon of self-organized phase transitions (SOPTs): repeated transitions between synchronous and asynchronous firing states. We further explore the mechanics generating SOPTs on the basis of synaptic weight dynamics. (interdisciplinary physics and related areas of science and technology)

Boltzmann-Gaussian transition under specific noise effect

International Nuclear Information System (INIS)

Anh, Chu Thuy; Lan, Nguyen Tri; Viet, Nguyen Ai

2014-01-01

It is observed that a short time data set of market returns presents almost symmetric Boltzmann distribution whereas a long time data set tends to show a Gaussian distribution. To understand this universal phenomenon, many hypotheses which are spreading in a wide range of interdisciplinary research were proposed. In current work, the effects of background fluctuations on symmetric Boltzmann distribution is investigated. The numerical calculation is performed to show that the Gaussian noise may cause the transition from initial Boltzmann distribution to Gaussian one. The obtained results would reflect non-dynamic nature of the transition under consideration.

Condensate-induced transitions and critical spin chains

NARCIS (Netherlands)

Månsson, T.; Lahtinen, V.; Suorsa, J.; Ardonne, E.

2013-01-01

We show that condensate-induced transitions between two-dimensional topological phases provide a general framework to relate one-dimensional spin models at their critical points. We demonstrate this using two examples. First, we show that two well-known spin chains, namely, the XY chain and the

Magnetic resonance of phase transitions

CERN Document Server

Owens, Frank J; Farach, Horacio A

1979-01-01

Magnetic Resonance of Phase Transitions shows how the effects of phase transitions are manifested in the magnetic resonance data. The book discusses the basic concepts of structural phase and magnetic resonance; various types of magnetic resonances and their underlying principles; and the radiofrequency methods of nuclear magnetic resonance. The text also describes quadrupole methods; the microwave technique of electron spin resonance; and the Mössbauer effect. Phase transitions in various systems such as fluids, liquid crystals, and crystals, including paramagnets and ferroelectrics, are also

Identification and Reduction of Turbomachinery Noise, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Communities near airports are often exposed to high noise levels due to low flying aircraft in the takeoff and landing phases of flight. Propulsion source noise is...

Melting along the Hugoniot and solid phase transition for Sn via sound velocity measurements

Science.gov (United States)

Song, Ping; Cai, Ling-cang; Tao, Tian-jiong; Yuan, Shuai; Chen, Hong; Huang, Jin; Zhao, Xin-wen; Wang, Xue-jun

2016-11-01

It is very important to determine the phase boundaries for materials with complex crystalline phase structures to construct their corresponding multi-phase equation of state. By measuring the sound velocity of Sn with different porosities, different shock-induced melting pressures along the solid-liquid phase boundary could be obtained. The incipient shock-induced melting of porous Sn samples with two different porosities occurred at a pressure of about 49.1 GPa for a porosity of 1.01 and 45.6 GPa for a porosity of 1.02, based on measurements of the sound velocity. The incipient shock-induced melting pressure of solid Sn was revised to 58.1 GPa using supplemental measurements of the sound velocity. Trivially, pores in Sn decreased the shock-induced melting pressure. Based on the measured longitudinal sound velocity data, a refined solid phase transition and the Hugoniot temperature-pressure curve's trend are discussed. No bcc phase transition occurs along the Hugoniot for porous Sn; further investigation is required to understand the implications of this finding.

Phase Noise Comparision of Short Pulse Laser Systems

Energy Technology Data Exchange (ETDEWEB)

S. Zhang; S. V. Benson; J. Hansknecht; D. Hardy; G. Neil; Michelle D. Shinn

2006-12-01

This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.

Impact of Bounded Noise and Rewiring on the Formation and Instability of Spiral Waves in a Small-World Network of Hodgkin-Huxley Neurons.

Science.gov (United States)

Yao, Yuangen; Deng, Haiyou; Ma, Chengzhang; Yi, Ming; Ma, Jun

2017-01-01

Spiral waves are observed in the chemical, physical and biological systems, and the emergence of spiral waves in cardiac tissue is linked to some diseases such as heart ventricular fibrillation and epilepsy; thus it has importance in theoretical studies and potential medical applications. Noise is inevitable in neuronal systems and can change the electrical activities of neuron in different ways. Many previous theoretical studies about the impacts of noise on spiral waves focus an unbounded Gaussian noise and even colored noise. In this paper, the impacts of bounded noise and rewiring of network on the formation and instability of spiral waves are discussed in small-world (SW) network of Hodgkin-Huxley (HH) neurons through numerical simulations, and possible statistical analysis will be carried out. Firstly, we present SW network of HH neurons subjected to bounded noise. Then, it is numerically demonstrated that bounded noise with proper intensity σ, amplitude A, or frequency f can facilitate the formation of spiral waves when rewiring probability p is below certain thresholds. In other words, bounded noise-induced resonant behavior can occur in the SW network of neurons. In addition, rewiring probability p always impairs spiral waves, while spiral waves are confirmed to be robust for small p, thus shortcut-induced phase transition of spiral wave with the increase of p is induced. Furthermore, statistical factors of synchronization are calculated to discern the phase transition of spatial pattern, and it is confirmed that larger factor of synchronization is approached with increasing of rewiring probability p, and the stability of spiral wave is destroyed.

Phase Transition and Thermodynamics of Ruthenium Diboride via First-Principles Calculations

International Nuclear Information System (INIS)

Fen, Luo; Yan, Cheng; Xiang-Rong, Chen; Guang-Fu, Ji

2009-01-01

The pressure induced phase transitions of RuB 2 from the OsB 2 -type structure to the ReB 2 -type structure are investigated by first-principles calculations based on the plane-wave basis set with the generalized gradient approximation for exchange and correlation. It is found that the phase transition occurs at 18.6 GPa. We predict the phase transition from the OsB 2 -type RuB 2 to the ReB 2 -type RuB 2 at high temperatures for the first time. The dependences of the heat capacity, thermal expansion coefficient, and the Grüneisen parameter on pressure and temperature for OsB 2 -type RuB 2 and ReB 2 -type RuB 2 are also investigated

Investigation of the resistive transition of MgB2 thin film through current noise

International Nuclear Information System (INIS)

Gandini, C; Rajteri, M; Portesi, C; Monticone, E; Masoero, A; Mazzetti, P

2006-01-01

In this paper we present measurements concerning the current noise produced during the resistive transition in a MgB 2 polycrystalline thin film. The power spectrum of the current noise, observed when the temperature is slowly changed across its critical value, presents a large electrical noise of the 1/f n type (n ≅ 3) over a quite wide range of frequencies. This noise may be considered as generated by the abrupt creation of resistive strips across the specimen constituted by grains which have undergone the resistive transition. A computer model that takes into account fluctations of the grain critical currents and of the number of grain per strips, has been developed to simulate the resistive transition and to evaluate the noise power spectrum. When the temperature is incresed and reaches its critical value, resistive strips are formed according to a percolative process, giving rise to resistance steps which are at the origin of the noise. The theoretical results obtained by this model are in good agreement, concerning both the shape and intensity of the noise power spectrum, with the experimental data directly measured on the specimen

Experimental Investigations of Noise Control in Planetary Gear Set by Phasing

Directory of Open Access Journals (Sweden)

S. H. Gawande

2014-01-01

Full Text Available Now a days reduction of gear noise and resulting vibrations has received much attention of the researchers. The internal excitation caused by the variation in tooth mesh stiffness is a key factor in causing vibration. Therefore to reduce gear noise and vibrations several techniques have been proposed in recent years. In this research the experimental work is carried out to study the effect of planet phasing on noise and subsequent resulting vibrations of Nylon-6 planetary gear drive. For this purpose experimental set-up was built and trials were conducted for two different arrangements (i.e., with phasing and without phasing and it is observed that the noise level and resulting vibrations were reduced by planet phasing arrangement. So from the experimental results it is observed that by applying the meshing phase difference one can reduce planetary gear set noise and vibrations.

Jet noise reduction via dispersed phase injection

Science.gov (United States)

Greska, Brent; Krothapalli, Anjaneyulu; Arakeri, Vijay

2001-11-01

A recently developed hot jet aeroacoustics facility at FMRL,FAMU-FSU College of Engineering has been used to study the far field noise characteristics of hot supersonic jets as influenced by the injection of a dispersed phase with low mass loading.The measured SPL from a fully expanded Mach 1.36 hot jet shows a peak value of about 139 dB at 40 deg from the jet axis.By injecting atomized water,the SPL are reduced in the angular region of about 30 deg to 50 deg with the maximum reduction being about 2 dB at 40 deg.However,with the use of non atomized aqueous polymer solution as a dispersed phase the noise levels are reduced over all angular positions by at least 1 dB with the maximum reduction being about 3 dB at 40 deg.The injection of a dispersed phase readily kills the screech; the initial results show promise and optimization studies are underway to find methods of further noise reduction.

Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

International Nuclear Information System (INIS)

Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua; Zhao, Lijuan

2016-01-01

Tm 3+ ions doped β-PbF 2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm 3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O h to D 4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm 3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field

Operation of transition-edge sensors with excess thermal noise

International Nuclear Information System (INIS)

Maasilta, I J; Kinnunen, K M; Nuottajaervi, A K; Leppaeniemi, J; Luukanen, A

2006-01-01

The superconducting transition-edge sensor (TES) is currently one of the most attractive choices for ultra-high resolution calorimetry in the keV x-ray band, and is being considered for future ESA and NASA missions. We have performed a study on the noise characteristics of Au/Ti bilayer TESs, at operating temperatures around ∼100 mK, with the SQUID readout at 1.5 K. Experimental results indicate that without modifications the back-action noise from the SQUID chip degrades the noise characteristics significantly. We present a simple and effective solution to the problem: by installing an extra shunt resistor which absorbs the excess radiation from the SQUID input, we have reduced the excess thermal (photon) noise power down by approximately a factor of five, allowing high resolution operation of the sensors

Soft x-ray induced femtosecond solid-to-solid phase transition

Czech Academy of Sciences Publication Activity Database

Tavella, F.; Höppner, H.; Tkachenko, V.; Medvedev, Nikita; Capotondi, F.; Golz, T.; Kai, Y.; Manfredda, M.; Pedersoli, E.; Prandolini, M.J.; Stojanovic, N.; Tanikawa, T.; Teubner, U.; Toleikis, S.; Ziaja, B.

Roč. 24, Sep (2017), s. 22-27 ISSN 1574-1818 Institutional support: RVO:68378271 Keywords : soft x-ray * ultrashort x-ray pulses * grafitization of diamond * non-thermal phase transition Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 0.908, year: 2016

Defect induced intermittency in the transit time dynamics generates 1/f noise in a trimer described by the discrete nonlinear Schroedinger equation

International Nuclear Information System (INIS)

Pando L, C.L.; Doedel, E.J.

2006-08-01

We investigate the nonlinear dynamics in a trimer, described by the one-dimensional discrete nonlinear Schrodinger equation (DNLSE), with periodic boundary conditions in the presence of a single on-site defect. We make use of numerical continuation to study different families of stationary and periodic solutions, which allows us to consider suitable perturbations. Taking into account a Poincare section, we are able to study the dynamics in both a thin stochastic layer solution and a global stochasticity solution. We find that the time series of the transit times, the time intervals to traverse some suitable sets in phase space, generate 1/f noise for both stochastic solutions. In the case of the thin stochastic layer solution, we find that transport between two almost invariant sets along with intermittency in small and large time scales are relevant features of the dynamics. These results are reflected in the behaviour of the standard map with suitable parameters. In both chaotic solutions, the distribution of transit times has a maximum and a tail with exponential decay in spite of the presence of long-range correlations in the time series. We motivate our study by considering a ring of weakly-coupled Bose-Einstein condensates (BEC) with attractive interactions, where inversion of populations between two spatially symmetric sites and phase locking take place in both chaotic solutions. (author)

Electric-field-induced phase transitions in co-doped Pb(Zr1−xTixO3 at the morphotropic phase boundary

Directory of Open Access Journals (Sweden)

Daniel J Franzbach

2014-02-01

Full Text Available The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr1−xTix0.98Nb0.02O3, 0.40 ≤ x ≤ 0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states.

Magnetic transitions and phases in random-anisotropy magnets

International Nuclear Information System (INIS)

Sellmyer, D.J.; Nafis, S.; O'Shea, M.J.

1988-01-01

The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed

Magnetic transitions and phases in random-anisotropy magnets

Science.gov (United States)

Sellmyer, D. J.; Nafis, S.; O'Shea, M. J.

1988-04-01

The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed.

Safety and efficacy of ebselen for the prevention of noise-induced hearing loss: a randomised, double-blind, placebo-controlled, phase 2 trial.

Science.gov (United States)

Kil, Jonathan; Lobarinas, Edward; Spankovich, Christopher; Griffiths, Scott K; Antonelli, Patrick J; Lynch, Eric D; Le Prell, Colleen G

2017-09-02

Noise-induced hearing loss is a leading cause of occupational and recreational injury and disease, and a major determinant of age-related hearing loss. No therapeutic agent has been approved for the prevention or treatment of this disorder. In animal models, glutathione peroxidase 1 (GPx1) activity is reduced after acute noise exposure. Ebselen, a novel GPx1 mimic, has been shown to reduce both temporary and permanent noise-induced hearing loss in preclinical studies. We assessed the safety and efficacy of ebselen for the prevention of noise-induced hearing loss in young adults in a phase 2 clinical trial. In this single-centre, randomised, double-blind, placebo-controlled phase 2 trial, healthy adults aged 18-31 years were randomly assigned (1:1:1:1) at the University of Florida (Gainsville, FL, USA) to receive ebselen 200 mg, 400 mg, or 600 mg, or placebo orally twice daily for 4 days, beginning 2 days before a calibrated sound challenge (4 h of pre-recorded music delivered by insert earphones). Randomisation was done with an allocation sequence generated by an independent third party. The primary outcome was mean temporary threshold shift (TTS) at 4 kHz measured 15 min after the calibrated sound challenge by pure tone audiometry; a reduction of 50% in an ebselen dose group compared with the placebo group was judged to be clinically relevant. All participants who received the calibrated sound challenge and at least one dose of study drug were included in the efficacy analysis. All randomly assigned patients were included in the safety analysis. This trial is registered with ClinicalTrials.gov, number NCT01444846. Between Jan 11, 2013, and March 24, 2014, 83 participants were enrolled and randomly assigned to receive ebselen 200 mg (n=22), 400 mg (n=20), or 600 mg (n=21), or placebo (n=20). Two participants in the 200 mg ebselen group were discontinued from the study before the calibrated sound challenge because they no longer met the inclusion criteria; these

Lévy noise improves the electrical activity in a neuron under electromagnetic radiation.

Science.gov (United States)

Wu, Juan; Xu, Yong; Ma, Jun

2017-01-01

As the fluctuations of the internal bioelectricity of nervous system is various and complex, the external electromagnetic radiation induced by magnet flux on membrane can be described by the non-Gaussian type distribution of Lévy noise. Thus, the electrical activities in an improved Hindmarsh-Rose model excited by the external electromagnetic radiation of Lévy noise are investigated and some interesting modes of the electrical activities are exhibited. The external electromagnetic radiation of Lévy noise leads to the mode transition of the electrical activities and spatial phase, such as from the rest state to the firing state, from the spiking state to the spiking state with more spikes, and from the spiking state to the bursting state. Then the time points of the firing state versus Lévy noise intensity are depicted. The increasing of Lévy noise intensity heightens the neuron firing. Also the stationary probability distribution functions of the membrane potential of the neuron induced by the external electromagnetic radiation of Lévy noise with different intensity, stability index and skewness papremeters are analyzed. Moreover, through the positive largest Lyapunov exponent, the parameter regions of chaotic electrical mode of the neuron induced by the external electromagnetic radiation of Lévy noise distribution are detected.

Lévy noise improves the electrical activity in a neuron under electromagnetic radiation.

Directory of Open Access Journals (Sweden)

Juan Wu

Full Text Available As the fluctuations of the internal bioelectricity of nervous system is various and complex, the external electromagnetic radiation induced by magnet flux on membrane can be described by the non-Gaussian type distribution of Lévy noise. Thus, the electrical activities in an improved Hindmarsh-Rose model excited by the external electromagnetic radiation of Lévy noise are investigated and some interesting modes of the electrical activities are exhibited. The external electromagnetic radiation of Lévy noise leads to the mode transition of the electrical activities and spatial phase, such as from the rest state to the firing state, from the spiking state to the spiking state with more spikes, and from the spiking state to the bursting state. Then the time points of the firing state versus Lévy noise intensity are depicted. The increasing of Lévy noise intensity heightens the neuron firing. Also the stationary probability distribution functions of the membrane potential of the neuron induced by the external electromagnetic radiation of Lévy noise with different intensity, stability index and skewness papremeters are analyzed. Moreover, through the positive largest Lyapunov exponent, the parameter regions of chaotic electrical mode of the neuron induced by the external electromagnetic radiation of Lévy noise distribution are detected.

Kuramoto-type phase transition with metronomes

International Nuclear Information System (INIS)

Boda, Sz; Ujvári, Sz; Tunyagi, A; Néda, Z

2013-01-01

Metronomes placed on the perimeter of a disc-shaped platform, which can freely rotate in a horizontal plane, are used for a simple classroom illustration of the Kuramoto-type phase transition. The rotating platform induces a global coupling between the metronomes, and the strength of this coupling can be varied by tilting the metronomes’ swinging plane relative to the radial direction on the disc. As a function of the tilting angle, a transition from spontaneously synchronized to unsynchronized states is observable. By varying the number of metronomes on the disc, finite-size effects are also exemplified. A realistic theoretical model is introduced and used to reproduce the observed results. Computer simulations of this model allow a detailed investigation of the emerging collective behaviour in this system. (paper)

Phase noise reduction by self-phase locking in semiconductor lasers using phase conjugate feedback

DEFF Research Database (Denmark)

Petersen, Lykke; Gliese, Ulrik Bo; Nielsen, Torben Nørskov

1994-01-01

noise takes a finite-low value corresponding to a state of first-order self-phase locking of the laser. As a result, the spectral shape of the laser signal does not remain Lorentzian but collapses around the carrier to a delta function with a close to carrier noise level of less than -137 d...

SIMMER-II analysis of transition-phase experiments

International Nuclear Information System (INIS)

Wehner, T.R.; Bell, C.R.

1985-01-01

Analyses of Los Alamos transition-phase experiments with the SIMMER-II computer code are reported. These transient boilup experiments simulated the recriticality-induced transient motion of a boiling pool of molten fuel, molten steel and steel vapor, within a subassembly duct in a liquid-metal fast breeder reactor during the transition phase of a core-disruptive accident. The two purposes of these experiments were to explore and reach a better understanding of fast reactor safety issues, and to provide data for SIMMER-II verification. Experimental data, consisting of four pressure traces and a high-speed movie, were recorded for four sets of initial conditions. For three of the four cases, SIMMER-II-calculated pressures compared reasonably well with the experimental pressures. After a modification to SIMMER-II's liquid-vapor drag correlation, the comparison for the fourth case was reasonable also. 12 refs., 4 figs

Electronic phase transitions

CERN Document Server

Kopaev, YuV

1992-01-01

Electronic Phase Transitions deals with topics, which are presently at the forefront of scientific research in modern solid-state theory. Anderson localization, which has fundamental implications in many areas of solid-state physics as well as spin glasses, with its influence on quite different research activities such as neural networks, are two examples that are reviewed in this book. The ab initio statistical mechanics of structural phase transitions is another prime example, where the interplay and connection of two unrelated disciplines of solid-state theory - first principle ele

Extra phase noise from thermal fluctuations in nonlinear optical crystals

DEFF Research Database (Denmark)

César, J. E. S.; Coelho, A.S.; Cassemiro, K.N.

2009-01-01

We show theoretically and experimentally that scattered light by thermal phonons inside a second-order nonlinear crystal is the source of additional phase noise observed in optical parametric oscillators. This additional phase noise reduces the quantum correlations and has hitherto hindered the d...

Phase noise estimation and mitigation for DCT-based coherent optical OFDM systems.

Science.gov (United States)

Yang, Chuanchuan; Yang, Feng; Wang, Ziyu

2009-09-14

In this paper, as an attractive alternative to the conventional discrete Fourier transform (DFT) based orthogonal frequency division multiplexing (OFDM), discrete cosine transform (DCT) based OFDM which has certain advantages over its counterpart is studied for optical fiber communications. As is known, laser phase noise is a major impairment to the performance of coherent optical OFDM (CO-OFDM) systems. However, to our knowledge, detailed analysis of phase noise and the corresponding mitigation methods for DCT-based CO-OFDM systems have not been reported yet. To address these issues, we analyze the laser phase noise in the DCT-based CO-OFDM systems, and propose phase noise estimation and mitigation schemes. Numerical results show that the proposal is very effective in suppressing phase noise and could significantly improve the performance of DCT-based CO-OFDM systems.

Pressure-induced transition in Tl2MoO4

International Nuclear Information System (INIS)

Machon, Denis; Friese, Karen; Breczewski, Tomasz; Grzechnik, Andrzej

2010-01-01

Tl 2 MoO 4 has been studied under high-pressure by X-ray diffraction, Raman spectroscopy, and optical absorption measurements. A first-order phase transition is observed at 3.5±0.5 GPa. The nature (ordered vs. disordered) of the high-pressure phase strongly depends on the local hydrostatic conditions. Optical absorption measurements tend to show that this transition is concomitant with an electronic structure transformation. Prior to the transition, single crystal X-ray diffraction shows that pressure induces interactions between MoO 4 fragments and the Mo coordination number tends to increase. In addition, the stereoactivity of the lone-pair electrons on the three symmetrically independent Tl-sites is not uniform; while for two sites the stereoactivity decreases with increasing pressures for the third site the stereoactivity increases. - Graphical Abstract: (up) Structural evolutions of Tl 2 MoO 4 in the low-pressure phase. (Down) Optical properties of the high-pressure phase as a function of pressure. Display Omitted

The phase transition in the SU(5) model at high temperatures

International Nuclear Information System (INIS)

Daniel, M.; Vayonakis, C.E.

1981-01-01

Within the minimum GUT model we have studied the nature of the fluctuation-induced transition between the SU(5) and the SU(3)sub(c) x SU(2) x U(1) phase which occurs at high temperatures. Our analysis is limited to the case when the phase transition occurs outside the critical (fluctuation-dominated) region. For this to happen the SU(5) model has to be in a mode analogous to the type I superconductor. This corresponds to having the scalar quartic couplings in the Higgs sector less than the squared gauge coupling. For generic values of the coupling constants the phase transition is found to be weakly first order. As we approach the boundaries for the region of the SU(3)sub(c) x SU(2) x U(1) phase, however, a strong first-order transition occurs. The SU(5) mode (analogous to the type II superconductor) when the phase transition occurs inside the fluctuation-dominated region has been recently studied by Ginsparg. His results together with ours show that there is a continuous merging of the type I mode into the type II mode. Finally our analysis elucidates some aspects of the monopole problem in grand unified theories. (orig.)

Dynamical response of the Ising model to the time dependent magnetic field with white noise

Science.gov (United States)

Akıncı, Ümit

2018-03-01

The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.

Unconventional phase transitions in liquid crystals

Science.gov (United States)

Kats, E. I.

2017-12-01

According to classical textbooks on thermodynamics or statistical physics, there are only two types of phase transitions: continuous, or second-order, in which the latent heat L is zero, and first-order, in which L ≠ 0. Present-day textbooks and monographs also mention another, stand-alone type—the Berezinskii-Kosterlitz-Thouless transition, which exists only in two dimensions and shares some features with first- and second-order phase transitions. We discuss examples of non-conventional thermodynamic behavior (i.e., which is inconsistent with the theoretical phase transition paradigm now universally accepted). For phase transitions in smectic liquid crystals, mechanisms for nonconventional behavior are proposed and the predictions they imply are examined.

Removing Background Noise with Phased Array Signal Processing

Science.gov (United States)

Podboy, Gary; Stephens, David

2015-01-01

Preliminary results are presented from a test conducted to determine how well microphone phased array processing software could pull an acoustic signal out of background noise. The array consisted of 24 microphones in an aerodynamic fairing designed to be mounted in-flow. The processing was conducted using Functional Beam forming software developed by Optinav combined with cross spectral matrix subtraction. The test was conducted in the free-jet of the Nozzle Acoustic Test Rig at NASA GRC. The background noise was produced by the interaction of the free-jet flow with the solid surfaces in the flow. The acoustic signals were produced by acoustic drivers. The results show that the phased array processing was able to pull the acoustic signal out of the background noise provided the signal was no more than 20 dB below the background noise level measured using a conventional single microphone equipped with an aerodynamic forebody.

Noise-induced hearing loss

Directory of Open Access Journals (Sweden)

Mariola Sliwinska-Kowalska

2012-01-01

Full Text Available Noise-induced hearing loss (NIHL still remains a problem in developed countries, despite reduced occupational noise exposure, strict standards for hearing protection and extensive public health awareness campaigns. Therefore NIHL continues to be the focus of noise research activities. This paper summarizes progress achieved recently in our knowledge of NIHL. It includes papers published between the years 2008-2011 (in English, which were identified by a literature search of accessible medical and other relevant databases. A substantial part of this research has been concerned with the risk of NIHL in the entertainment sector, particularly in professional, orchestral musicians. There are also constant concerns regarding noise exposure and hearing risk in "hard to control" occupations, such as farming and construction work. Although occupational noise has decreased since the early 1980s, the number of young people subject to social noise exposure has tripled. If the exposure limits from the Noise at Work Regulations are applied, discotheque music, rock concerts, as well as music from personal music players are associated with the risk of hearing loss in teenagers and young adults. Several recent research studies have increased the understanding of the pathomechanisms of acoustic trauma, the genetics of NIHL, as well as possible dietary and pharmacologic otoprotection in acoustic trauma. The results of these studies are very promising and offer grounds to expect that targeted therapies might help prevent the loss of sensory hair cells and protect the hearing of noise-exposed individuals. These studies emphasize the need to launch an improved noise exposure policy for hearing protection along with developing more efficient norms of NIHL risk assessment.

Effect of realistic and filtered stellar photometric noise on the detection of moons using photometric transit timing

Directory of Open Access Journals (Sweden)

Lewis K.

2011-02-01

Full Text Available The photometric transit timing technique was proposed by Szabó et al. (2006 as a method for discovering moons of transiting extrasolar planets. In the preliminary analysis of this technique, it was assumed that the noise in the transit lightcurve was well described by uncorrelated white noise. However, this assumption is not necessarily realistic. To determine the effect of using more realistic lightcurves, transit timing uncertainties are calculated for the case of white noise, measured solar photometric noise and measured solar photometric noise that has been filtered. It is found that for light curves contaminated with realistic photometric noise, the transit timing uncertainties are dramatically increased (and thus moon detection reduced. In addition, we find that while filtering reduced this problem, it did not negate it.

Federal Transit Administration's noise and vibration Guidance Manual: Updates after 10 years of experience

Science.gov (United States)

Hanson, Carl E.

2005-09-01

In April 1995, the Federal Transit Administration of the U.S. Department of Transportation issued its guidance manual, ``Transit Noise and Vibration Impact Assessment.'' The manual was written to provide direction for the preparation of noise and vibration sections of environmental documents for public transportation projects in the interest of promoting quality and uniformity in assessments. In the 10 years since its release, the guidance manual has been used as the basis of noise and vibration assessments in over 80 environmental documents and has been used worldwide as a standard method for performing transit noise analyses. An updated version has recently been prepared that takes account of improvements in tools, changes in the environmental assessment procedures, modifications of impact criteria, and experience with mitigation measures. These factors, and other background information, will be discussed to provide insight regarding the revisions in the new edition.

Strongly first-order electroweak phase transition and classical scale invariance

Science.gov (United States)

Farzinnia, Arsham; Ren, Jing

2014-10-01

In this work, we examine the possibility of realizing a strongly first-order electroweak phase transition within the minimal classically scale-invariant extension of the standard model (SM), previously proposed and analyzed as a potential solution to the hierarchy problem. By introducing one complex gauge-singlet scalar and three (weak scale) right-handed Majorana neutrinos, the scenario was successfully rendered capable of achieving a radiative breaking of the electroweak symmetry (by means of the Coleman-Weinberg mechanism), inducing nonzero masses for the SM neutrinos (via the seesaw mechanism), presenting a pseudoscalar dark matter candidate (protected by the CP symmetry of the potential), and predicting the existence of a second CP-even boson (with suppressed couplings to the SM content) in addition to the 125 GeV scalar. In the present treatment, we construct the full finite-temperature one-loop effective potential of the model, including the resummed thermal daisy loops, and demonstrate that finite-temperature effects induce a first-order electroweak phase transition. Requiring the thermally driven first-order phase transition to be sufficiently strong at the onset of the bubble nucleation (corresponding to nucleation temperatures TN˜100-200 GeV) further constrains the model's parameter space; in particular, an O(0.01) fraction of the dark matter in the Universe may be simultaneously accommodated with a strongly first-order electroweak phase transition. Moreover, such a phase transition disfavors right-handed Majorana neutrino masses above several hundreds of GeV, confines the pseudoscalar dark matter masses to ˜1-2 TeV, predicts the mass of the second CP-even scalar to be ˜100-300 GeV, and requires the mixing angle between the CP-even components of the SM doublet and the complex singlet to lie within the range 0.2≲sinω ≲0.4. The obtained results are displayed in comprehensive exclusion plots, identifying the viable regions of the parameter space

Density-functional theory study of the pressure-induced phase transition in hydronitrogen compound N{sub 4}H{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Liu, Qi-Jun, E-mail: qijunliu@home.swjtu.edu.cn [Bond and Band Engineering Group, Sichuan Provincial Key Laboratory (for Universities) of High Pressure Science and Technology, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, Ning-Chao; Sun, Yan-Yun; Zhang, Ming-Jian; Liu, Fu-Sheng [Bond and Band Engineering Group, Sichuan Provincial Key Laboratory (for Universities) of High Pressure Science and Technology, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Liu, Zheng-Tang [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China)

2014-03-01

Using first-principles density-functional theory, we have investigated the pressure-induced phase transition in hydronitrogen compound N{sub 4}H{sub 4} and discussed the potential tetragonal structure. We find that tetragonal structure with P4{sub 2}/n space group is mechanically stable and ductile. The thermodynamic stability of Pmna>P1{sup ¯}>P4{sub 2}/n>P2{sub 1}/m has been obtained. With increasing pressure, the phase transition pressures of T{sub Pmna→P4{sub 2/n}}, T{sub P4{sub 2/n→Pmna}}, T{sub Pmna→P1{sup ¯}} and T{sub P1{sup ¯}→P2{sub 1/m}} are 5.6, 15.0, 30.0 and 69.2 GPa, respectively, which are in agreement with the available data. Moreover, the mechanical stability of four structures under pressure has been analyzed.

Phase transition induced anelasticity in Fe–Ga alloys with 25 and 27%Ga

Energy Technology Data Exchange (ETDEWEB)

Golovin, I.S., E-mail: i.golovin@misis.ru [National University of Science and Technology “MISIS”, Leninsky ave. 4, 119049, Moscow (Russian Federation); Balagurov, A.M., E-mail: bala@nf.jinr.ru [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980, Dubna (Russian Federation); Bobrikov, I.A. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980, Dubna (Russian Federation); Palacheva, V.V. [National University of Science and Technology “MISIS”, Leninsky ave. 4, 119049, Moscow (Russian Federation); Cifre, J. [Universitat de les Illes Balears, Ctra. De Valldemossa, km.7.5, E-07122, Palma de Mallorca (Spain)

2016-08-05

Neutron diffraction and mechanical spectroscopy techniques were applied to study phase transitions in Fe–Ga alloys with 25 and 27 at.% Ga. The following sequences of phase transitions at continuous heating and subsequent cooling in the 20–900 °C temperature range were recorded: D0{sub 3} → L1{sub 2} (limited amount) → A2(B2) was recorded at heating and A2(B2) → D0{sub 3} at cooling for Fe-24.8Ga alloy, and the D0{sub 3} → L1{sub 2} → D0{sub 19} → A2(B2) was recorded at heating and A2(B2) → L1{sub 2} at cooling for Fe-27.4Ga alloy. Thus, the difference in 2.6 at.%Ga between two studied compositions with D0{sub 3} structure leads to their different structures after heating to 900 °C. These transition sequences determine different temperature dependencies of elastic and anelastic properties. The D0{sub 3} → A2(B2) transition (in Fe-25Ga) does not lead to a well-pronounced anelastic effect, in contrast the D0{sub 3} → L1{sub 2} transition (in Fe-27Ga) generates internal stresses due to a different rate of an increase in the lattice parameter with temperature and leads to a well-pronounced transient internal friction effect. - Highlights: • Neutron diffraction technique is used to study in situ phase transitions in Fe-25 and 27 at.% Ga. • D0{sub 3} → L1{sub 2} → D0{sub 19} → A2/B2 transitions were recorded at instant heating in Fe-27 at.% Ga. • D0{sub 3} → L1{sub 2} (limited amount) → A2(B2) was recorded at instant heating in Fe-25 at.% Ga • The D0{sub 3} → L1{sub 2} transition generates internal stresses and leads to elastic and anelastic response.

Chronic lead exposure induces cochlear oxidative stress and potentiates noise-induced hearing loss.

Science.gov (United States)

Jamesdaniel, Samson; Rosati, Rita; Westrick, Judy; Ruden, Douglas M

2018-08-01

Acquired hearing loss is caused by complex interactions of multiple environmental risk factors, such as elevated levels of lead and noise, which are prevalent in urban communities. This study delineates the mechanism underlying lead-induced auditory dysfunction and its potential interaction with noise exposure. Young-adult C57BL/6 mice were exposed to: 1) control conditions; 2) 2 mM lead acetate in drinking water for 28 days; 3) 90 dB broadband noise 2 h/day for two weeks; and 4) both lead and noise. Blood lead levels were measured by inductively coupled plasma mass spectrometry analysis (ICP-MS) lead-induced cochlear oxidative stress signaling was assessed using targeted gene arrays, and the hearing thresholds were assessed by recording auditory brainstem responses. Chronic lead exposure downregulated cochlear Sod1, Gpx1, and Gstk1, which encode critical antioxidant enzymes, and upregulated ApoE, Hspa1a, Ercc2, Prnp, Ccl5, and Sqstm1, which are indicative of cellular apoptosis. Isolated exposure to lead or noise induced 8-12 dB and 11-25 dB shifts in hearing thresholds, respectively. Combined exposure induced 18-30 dB shifts, which was significantly higher than that observed with isolated exposures. This study suggests that chronic exposure to lead induces cochlear oxidative stress and potentiates noise-induced hearing impairment, possibly through parallel pathways. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Residual phase noise measurements of the input section in a receiver

International Nuclear Information System (INIS)

Mavric, Uros; Chase, Brian; Fermilab

2007-01-01

If not designed properly, the input section of an analog down-converter can introduce phase noise that can prevail over other noise sources in the system. In the paper we present residual phase noise measurements of a simplified input section of a classical receiver that is composed of various commercially available mixers and driven by an LO amplifier

Giant Suppression of the Activation Rate in Dynamical Systems Exhibiting Chaotic Transitions

Science.gov (United States)

Gac, J. M.; Xafebrowski, J. J.

2008-05-01

The phenomenon of giant suppression of activation, when two or more correlated noise signals act on the system, was found a few years ago in dynamical bistable or metastable systems. When the correlation between these noise signals is strong enough and the amplitudes of the noise are chosen correctly --- the life time of the metastable state may be longer than in the case of the application of only a single noise even by many orders of magnitude. In this paper, we investigate similar phenomena in systems exhibiting several chaotic transitions: Pomeau--Manneville intermittency, boundary crisis and interior crisis induced intermittency. Our goal is to show that, in these systems the application of two noise components with the proper choice of the parameters in the case of intermittency can also lengthen the mean laminar phase length or, in the case of boundary crisis, lengthen the time the trajectory spends on the pre-crisis attractor. In systems with crisis induced intermittency, we introduce a new phenomenon we called quasi-deterministic giant suppression of activation in which the lengthening of the laminar phase lengths is caused not by the action of two correlated noise signals but by a single noise term which is correlated with one of the chaotic variables of the system.

Effects of Colored Noise on Periodic Orbits in a One-Dimensional Map

Science.gov (United States)

Li, Feng-Guo; Ai, Bao-Quan

2011-06-01

Noise can induce inverse period-doubling transition and chaos. The effects of the colored noise on periodic orbits, of the different periodic sequences in the logistic map, are investigated. It is found that the dynamical behaviors of the orbits, induced by an exponentially correlated colored noise, are different in the mergence of transition, and the effects of the noise intensity on their dynamical behaviors are different from the effects of the correlation time of noise. Remarkably, the noise can induce new periodic orbits, namely, two new orbits emerge in the period-four sequence at the bifurcation parameter value μ = 3.5, four new orbits in the period-eight sequence at μ = 3.55, and three new orbits in the period-six sequence at μ = 3.846, respectively. Moreover, the dynamical behaviors of the new orbits clearly show the resonancelike response to the colored noise.

Effects of Colored Noise on Periodic Orbits in a One-Dimensional Map

International Nuclear Information System (INIS)

Li Fengguo; Ai Baoquan

2011-01-01

Noise can induce inverse period-doubling transition and chaos. The effects of the colored noise on periodic orbits, of the different periodic sequences in the logistic map, are investigated. It is found that the dynamical behaviors of the orbits, induced by an exponentially correlated colored noise, are different in the mergence of transition, and the effects of the noise intensity on their dynamical behaviors are different from the effects of the correlation time of noise. Remarkably, the noise can induce new periodic orbits, namely, two new orbits emerge in the period-four sequence at the bifurcation parameter value μ = 3.5, four new orbits in the period-eight sequence at μ = 3.55, and three new orbits in the period-six sequence at μ = 3.846, respectively. Moreover, the dynamical behaviors of the new orbits clearly show the resonancelike response to the colored noise. (general)

Epidemiology of noise-induced tinnitus and the attitudes and beliefs towards noise and hearing protection in adolescents.

Directory of Open Access Journals (Sweden)

Annick Gilles

Full Text Available BACKGROUND AND OBJECTIVES: Previous research showed an increase of noise-induced symptoms in adolescents. Permanent tinnitus as a consequence of loud music exposure is usually considered as noise-induced damage. The objective was to perform an epidemiological study in order to obtain prevalence data of permanent noise-induced tinnitus as well as temporary tinnitus following noise exposure in a young population. In addition the attitudes and beliefs towards noise and hearing protection were evaluated in order to explain the use/non-use of hearing protection in a young population. METHODS: A questionnaire was completed by 3892 high school students (mean age: 16.64 years old, SD: 1.29 years. The prevalence of temporary and permanent tinnitus was assessed. In addition the 'Youth Attitudes to Noise Scale' and the 'Beliefs About Hearing Protection and Hearing Loss' were used in order to assess the attitudes and beliefs towards noise and hearing protection respectively. RESULTS: The prevalence of temporary noise-induced tinnitus and permanent tinnitus in high school students was respectively 74.9% and 18.3%. An increasing prevalence of temporary tinnitus with age was present. Most students had a 'neutral attitude' towards loud music and the use of hearing protection was minimal (4.7%. The limited use of hearing protection is explained by a logistic regression analysis showing the relations between certain parameters and the use of hearing protection. CONCLUSIONS: Despite the very high prevalence of tinnitus in such a young population, the rate of hearing protection use and the knowledge about the risks of loud music is extremely low. Future preventive campaigns should focus more on tinnitus as a warning signal for noise-induced damage and emphasize that also temporary symptoms can result in permanent noise-induced damage.

Structural phase transitions and Huang scattering

International Nuclear Information System (INIS)

Yamada, Yasusada

1980-01-01

The usefulness of the application of the concept of Huang scattering to the understandings of the origin of diffuse scatterings near structural phase transitions are discussed. It is pointed out that in several phase transitions, the observed diffuse scatterings can not be interpreted in terms of critical fluctuations of the order parameters associated with the structural phase transitions, and that they are rather interpreted as Huang scattering due to random distribution of individual order parameter which is 'dressed' by strain fields. Examples to show effective applications of this concept to analyze the experimental X-ray data and whence to understand microscopic mechanisms of structural phase transitions are presented. (author)

A calorimetric particle detector using an iridium superconducting phase transition thermometer

International Nuclear Information System (INIS)

Frank, M.; Dummer, D.; Cooper, S.; Igalson, J.; Proebst, F.; Seidel, W.

1994-01-01

We report on a calorimetric particles detector consisting of an 18.3 g silicon crystal and an iridium superconducting phase transition thermometer. The cryogenic calorimeter and the associated apparatus are described in detail. The pulses from irradiation with an α-particle source have a large unexpected overshoot in addition to the component expected from a naive thermal model. The pulse height spectrum displays an energy resolution of 1 percent FWHM at 6 MeV and good linearity. The noise, electrothermal feedback, and position dependence are discussed. (orig.)

The effect of point defects on ferroelastic phase transition of lanthanum-doped calcium titanate ceramics

International Nuclear Information System (INIS)

Ni, Yan; Zhang, Zhen; Wang, Dong; Wang, Yu; Ren, Xiaobing

2013-01-01

Highlights: ► The effect of point defects on phase transitions in Ca (1−x) La 2x/3 TiO 3 was studied. ► When x = 0.45, normal ferroelastic phase transition happens. ► When x = 0.7, a “glassy-like” frozen process appears. ► Point defects weaken the thermodynamic stability of ferroelastic phase. ► Point defects induce a “glassy-like” frozen process. -- Abstract: In the present paper, La-doped CaTiO 3 is studied to investigate the effect of point defects on ferroelastic phase transition of the ceramics. The dynamic mechanical measurements show that the transition temperature of the orthorhombic to tetragonal phase transition of Ca (1−x) La 2x/3 TiO 3 decreases with increasing dopant (La) concentration x. The samples with the dopant content of x = 0.45 and 0.7 exhibit different structure evolution features during their transition processes as revealed by in situ powder X-ray diffraction (XRD) measurement. Moreover, when x = 0.7, the storage modulus shows a frequency-dependent minimum at T g , which can be well fitted with the Vogel–Fulcher relation, and the corresponding internal friction also exhibits a frequency-dependent peak within the same temperature regime. These results thus indicate that doping La suppresses ferroelastic phase transition in CaTiO 3 and induces a “glassy-like” behavior in Ca (1−x) La 2x/3 TiO 3 , which is similar to “strain glass” in Ni-doped Ti 50−x Ni 50+x

Social Goal Orientations, Interpersonal Stress, and Depressive Symptoms among Early Adolescents in Japan: A Test of the Diathesis-Stress Model Using the Trichotomous Framework of Social Goal Orientations

Science.gov (United States)

Kuroda, Yuji; Sakurai, Shigeo

2011-01-01

This longitudinal study investigated whether depression among early adolescents (aged 12-14 years, N = 116; 65 girls) can be predicted by interactions between social goal orientations and interpersonal stress. Based on Kuroda and Sakurai (2001), this study applied Elliot and Harackiewicz's (1996) trichotomous framework of achievement goals to…

Quasi-dynamic pressure and temperature initiated βδ solid phase transitions in HMX

Science.gov (United States)

Zaug, Joseph M.; Farber, Daniel L.; Craig, Ian M.; Blosch, Laura L.; Shuh, David K.; Hansen, Donald W.; Aracne-Ruddle, Chantel M.

2000-04-01

The phase transformation of β-HMX (>0.5% RDX) to δ phase has been studied for over twenty years and more recently with an high-contrast optical second harmonic generation technique. Shock studies of the plastic binder composites of HMX have indicated that the transition is perhaps irreversible, a result that concurs with the static pressure results published by F. Goetz et al. [1] in 1978. However, the stability field favors the β polymorph over δ as pressure is increased (up to 5.4 GPa) along any thermodynamically reasonable isotherm. In this experiment, strict control of pressure and temperature is maintained while x-ray and optical diagnostics are applied to monitor the conformational dynamics of HMX. Unlike the temperature induced β→δ transition, the pressure induced is heterogeneous in nature. The 1 bar 25 °C δ→β transition is not immediate, occuring over tens of hours. Transition points and kinetics are path dependent and consequently this paper describes our work in progress.

Kinetics of the stress induced phase transition in quartz by real-time neutron scattering

International Nuclear Information System (INIS)

Gibhardt, H.; Eckold, G.; Guethoff, F.

1999-01-01

Complete text of publication follows. The stability regime of the incommensurate phase of quartz is influenced by uniaxial stress. Hence, the phase transition can be induced under isothermal conditions by the application of external mechanical forces. Using real-time neutron scattering the time evolution of structural changes is investigated id detail during stress variations. The time dependent behaviour of the satellite reflection is compared with that one of the fundamental Bragg reflection which - via primary extinction - gives information about the perfection of the crystal. On increasing stress the perfection of the lattice is destroyed immediately while the modulated structure is built up with a delay of about 1 s. Decreasing the stress leads to a reverse behaviour. Moreover, there is evidence that under periodical load residual non-relaxed strain fields survive leading to a different temperature dependence as compared to static conditions. This finding is compatible with pronounced hysteresis effects observed under cycling stress. It is argued that these residual strains are associated with non-relaxed topological 4-line defects, that drive the structural changes in quartz (1). (author)

Voltage-Controlled Topotactic Phase Transition in Thin-Film SrCoOx Monitored by In Situ X-ray Diffraction.

Science.gov (United States)

Lu, Qiyang; Yildiz, Bilge

2016-02-10

Topotactic phase transition of functional oxides induced by changes in oxygen nonstoichiometry can largely alter multiple physical and chemical properties, including electrical conductivity, magnetic state, oxygen diffusivity, and electrocatalytic reactivity. For tuning these properties reversibly, feasible means to control oxygen nonstoichiometry-dependent phase transitions in functional oxides are needed. This paper describes the use of electrochemical potential to induce phase transition in strontium cobaltites, SrCoOx (SCO) between the brownmillerite (BM) phase, SrCoO₂.₅, and the perovskite (P) phase, SrCoO₃₋δ. To monitor the structural evolution of SCO, in situ X-ray diffraction (XRD) was performed on an electrochemical cell having (001) oriented thin-film SrCoOx as the working electrode on a single crystal (001) yttria-stabilized zirconia electrolyte in air. In order to change the effective pO₂ in SCO and trigger the phase transition from BM to P, external electrical biases of up to 200 mV were applied across the SCO film. The phase transition from BM to P phase could be triggered at a bias as low as 30 mV, corresponding to an effective pO₂ of 1 atm at 500 °C. The phase transition was fully reversible and the epitaxial film quality was maintained after reversible phase transitions. These results demonstrate the use of electrical bias to obtain fast and easily accessible switching between different phases as well as distinct physical and chemical properties of functional oxides as exemplified here for SCO.

Diamond to β-Sn phase transition of silicon under hydrostatic and nonhydrostatic compressions

International Nuclear Information System (INIS)

Durandurdu, Murat

2008-01-01

We have carried out constant pressure ab initio simulations to study the pressure-induced phase transition of silicon. The diamond to β-Sn phase change under hydrostatic pressure is successfully observed in the simulation. The transformation is based on a fourfold coordinated tetragonal intermediate state having the space group I4 1 /amd. The energy barrier for the transformation is calculated to be about 0.35 eV/atom. Additionally, we investigate the influence of nonhydrostatic compressions on the phase transition of silicon and find that up to 20% stress deviations, silicon converts to a β-Sn structure with a reduced transition pressure. The triaxial compressions cause more reduction in the transition pressure than the uniaxial compressions. The transformation mechanism is practically identical under both hydrostatic and nonhydrostatic conditions

Modern theories of phase transitions

International Nuclear Information System (INIS)

Rajaraman, R.

1979-01-01

Modern applications of the ideas of phase transitions to nuclear systems and the modern techniques as applied to familiar phase transitions in solid-state physics are discussed with illustrations. The phenomenon of pion condensation in nuclei and neutron stars, is presented as an example of phase transitions in nuclear systems. The central physical ideas behind this subject as well as techniques used to tackle it are broadly summarised. It is pointed out that unlike familiar examples of ferromagnetism or superconductivity, the order parameter here has spatial variation even in the ground state. Possible experimental consequences are discussed. As an example of the second category, the use of renormalisation group techniques in solid state physics is reviewed. The basic idea behind the renormalisation group in the infra-red (thermodynamic) limit is presented. The observed universality and scaling of critical exponents in second order phase transitions is explained in a model-independent way. (auth.)

Pressure-induced decoupling of the order-disorder and displacive contributions to the phase transition in diguanidinium tetrachlorostannate

DEFF Research Database (Denmark)

Szafranski, M.; Ståhl, Kenny

2000-01-01

The crystals of diguanidinium tetrachlorostannate [C(NH2)(3)](2)(+).SnCl4-2, were studied by single-crystal x-ray diffraction at various temperatures and by calorimetric and dielectric measurements at ambient and high hydrostatic pressures. At room temperature the crystal structure is orthorhombic......) cations. At ambient pressure the crystals undergo two first-order phase transitions at 354.8 and 395.4 K. The former, between two orthorhombic phases (Pbca --> Cmca), is characterized by antiphase displacement of the double sheets along the b direction of the low-temperature unit cell which is coupled...... to dynamical disordering of G(2) and transformation of its hydrogen bonding scheme. At elevated pressures the coupling between the displacive and order-disorder contributions is modified and its breaking near a triple point at 180 MPa and 270 K results in a pressure-induced phase observed between Pbca and Cmca...

Constructive influence of noise flatness and friction on the resonant behavior of a harmonic oscillator with fluctuating frequency.

Science.gov (United States)

Laas, Katrin; Mankin, Romi; Rekker, Astrid

2009-05-01

The influences of noise flatness and friction coefficient on the long-time behavior of the first two moments and the correlation function for the output signal of a harmonic oscillator with fluctuating frequency subjected to an external periodic force are considered. The colored fluctuations of the oscillator frequency are modeled as a trichotomous noise. The study is a follow up of the previous investigation of a stochastic oscillator [Phys. Rev. E 78, 031120 (2008)], where the connection between the occurrence of energetic instability and stochastic multiresonance is established. Here we report some unexpected results not considered in the previous work. Notably, we have found a nonmonotonic dependence of several stochastic resonance characteristics such as spectral amplification, variance of the output signal, and signal-to-noise ratio on the friction coefficient and on the noise flatness. In particular, in certain parameter regions spectral amplification exhibits a resonancelike enhancement at intermediate values of the friction coefficient.

Multiple pathways in pressure-induced phase transition of coesite

Science.gov (United States)

Liu, Wei; Wu, Xuebang; Liu, Changsong; Miranda, Caetano R.; Scandolo, Sandro

2017-01-01

High-pressure single-crystal X-ray diffraction method with precise control of hydrostatic conditions, typically with helium or neon as the pressure-transmitting medium, has significantly changed our view on what happens with low-density silica phases under pressure. Coesite is a prototype material for pressure-induced amorphization. However, it was found to transform into a high-pressure octahedral (HPO) phase, or coesite-II and coesite-III. Given that the pressure is believed to be hydrostatic in two recent experiments, the different transformation pathways are striking. Based on molecular dynamic simulations with an ab initio parameterized potential, we reproduced all of the above experiments in three transformation pathways, including the one leading to an HPO phase. This octahedral phase has an oxygen hcp sublattice featuring 2 × 2 zigzag octahedral edge-sharing chains, however with some broken points (i.e., point defects). It transforms into α-PbO2 phase when it is relaxed under further compression. We show that the HPO phase forms through a continuous rearrangement of the oxygen sublattice toward hcp arrangement. The high-pressure amorphous phases can be described by an fcc and hcp sublattice mixture. PMID:29162690

Stochastic synchronization of neuronal populations with intrinsic and extrinsic noise.

KAUST Repository

Bressloff, Paul C

2011-05-03

We extend the theory of noise-induced phase synchronization to the case of a neural master equation describing the stochastic dynamics of an ensemble of uncoupled neuronal population oscillators with intrinsic and extrinsic noise. The master equation formulation of stochastic neurodynamics represents the state of each population by the number of currently active neurons, and the state transitions are chosen so that deterministic Wilson-Cowan rate equations are recovered in the mean-field limit. We apply phase reduction and averaging methods to a corresponding Langevin approximation of the master equation in order to determine how intrinsic noise disrupts synchronization of the population oscillators driven by a common extrinsic noise source. We illustrate our analysis by considering one of the simplest networks known to generate limit cycle oscillations at the population level, namely, a pair of mutually coupled excitatory (E) and inhibitory (I) subpopulations. We show how the combination of intrinsic independent noise and extrinsic common noise can lead to clustering of the population oscillators due to the multiplicative nature of both noise sources under the Langevin approximation. Finally, we show how a similar analysis can be carried out for another simple population model that exhibits limit cycle oscillations in the deterministic limit, namely, a recurrent excitatory network with synaptic depression; inclusion of synaptic depression into the neural master equation now generates a stochastic hybrid system.

Crystalline-to-amorphous phase transition in irradiated silicon

International Nuclear Information System (INIS)

Seidman, D.N.; Averback, R.S.; Okamoto, P.R.; Baily, A.C.

1986-01-01

The amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e - ) and/or ion irradiated silicon (Si). The irradiations were performed in situ in the Argonne High Voltage Microscope-Tandem Facility. The irradiation of Si, at 0 K, with 1-MeV e - to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at 0 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of approx.0.37 dpa. Alternatively a dual irradiation, at 10 0 K, with 1.0-MeV e - and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa - where the ratio of the displacement rates for e - to ions was approx.0.5 - resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of damage and the mobilities of point defects

Application of Machine Learning Techniques for Amplitude and Phase Noise Characterization

DEFF Research Database (Denmark)

Zibar, Darko; de Carvalho, Luis Henrique Hecker; Piels, Molly

2015-01-01

In this paper, tools from machine learning community, such as Bayesian filtering and expectation maximization parameter estimation, are presented and employed for laser amplitude and phase noise characterization. We show that phase noise estimation based on Bayesian filtering outperforms...

On the search for experimentally observed grain boundary phase transitions

International Nuclear Information System (INIS)

Balluffi, R.W.; Hsieh, T.E.

1987-07-01

The phase space for a heterogeneous system containing a grain boundary involves a relatively large number of variables (i.e., at least six plus the number of components), and it is therefore conceptually possible to induce a large variety of grain boundary phase transitions by selectively varying these parameters. Despite this, a review of the literature reveals that there have been virtually no clear-cut experimental observations of transitions reported in which the boundary structure has been observed as a function of time under well defined conditions. In current work, we are searching for roughening/faceting transitions and melting transitions for boundaries in Al by hot stage transmission electron microscopy. A clear example of a reversible roughening/faceting transition has been found. No evidence for melting has been found for temperatures as high as 0.96 T/sub m/ (by monitoring GBD core delocalization in several special boundaries with Σ ≤ 13) or 0.999 T/sub m/ (by observing the local diffraction contrast at general boundaries in polycrystalline specimens)

Topological phase transitions and quantum Hall effect in the graphene family

Science.gov (United States)

Ledwith, P.; Kort-Kamp, W. J. M.; Dalvit, D. A. R.

2018-04-01

Monolayer staggered materials of the graphene family present intrinsic spin-orbit coupling and can be driven through several topological phase transitions using external circularly polarized lasers and static electric or magnetic fields. We show how topological features arising from photoinduced phase transitions and the magnetic-field-induced quantum Hall effect coexist in these materials and simultaneously impact their Hall conductivity through their corresponding charge Chern numbers. We also show that the spectral response of the longitudinal conductivity contains signatures of the various phase-transition boundaries, that the transverse conductivity encodes information about the topology of the band structure, and that both present resonant peaks which can be unequivocally associated with one of the four inequivalent Dirac cones present in these materials. This complex optoelectronic response can be probed with straightforward Faraday rotation experiments, allowing the study of the crossroads between quantum Hall physics, spintronics, and valleytronics.

High-pressure phase transitions of deep earth materials

International Nuclear Information System (INIS)

Hirose, Kei

2009-01-01

Recent developments in synchrotron XRD measurements combined with laser-heated diamond-anvil cell (LHDAC) techniques have enabled us to search for a novel phase transition at extremely high pressure and temperature. A phase transition from MgSiO 3 perovskite to post-perovskite was discovered through a drastic change in XRD patterns above 120 GPa and 2500 K, corresponding to the condition in the lowermost mantle (Murakami et al., 2004; Oganov and Ono, 2004). A pressure-induced phase transformation from ABO 3 -type perovskite to any denser structures was not known at that time. This new MgSiO 3 polymorph called post-perovskite has an orthorhombic symmetry (space group: Cmcm) with a sheet-stacking structure. The Mg site in post-perovskite is smaller than that in perovskite, which results in a volume reduction by 1.0-1.5% from perovskite structure. The electrical conductivity of post-perovskite is higher by three orders of magnitude than that of perovskite at similar pressure range (Ohta et al., 2008). This is likely due to a shorter Fe-Fe distance in post-perovskite structure, while conduction mechanism is yet to be further examined. Phase transition boundary between perovskite and post-perovskite has been determined in a wide temperature range up to 4400 K at 170 GPa (Tateno et al., 2008). Phase relations of Fe alloys have been also studied at core pressures (>135 GPa), although the generation of high temperature is more difficult at higher pressures. A new high-pressure B2 phase of B2 phase of FeS was recently discovered above 180 GPa (Sata et al., 2008). The Fe-Ni alloys have a wide pressure-temperature stability field of fcc phase at the core pressure range, depending on the Ni content (Kuwayama et al., 2008). (author)

Raman-scattering observation of the rutile-to-CaCl2 phase transition in RuO2

International Nuclear Information System (INIS)

Rosenblum, S.S.; Weber, W.H.; Chamberland, B.L.

1997-01-01

Using a diamond-anvil cell, we have probed the pressure-induced rutile-to-CaCl 2 ferroelastic phase transition in RuO 2 with Raman spectroscopy. The transition is marked by a splitting of the degenerate E g mode of the rutile phase into two nondegenerate components and by an abrupt change in the Grueneisen parameters for all the phonons. The behavior of this splitting shows good agreement with Landau close-quote s theory for a second-order phase transition, application of which yields a transition pressure of 11.8±0.3 GPa. copyright 1997 The American Physical Society

Vacuum instability, anomalous asymmetry effect, phase transition and band mixing in strongly deformed nuclei

International Nuclear Information System (INIS)

Lin, L.; Sperber, D.

1976-01-01

In two recent papers the instability of the quasi-particle vacuum was related to the high-spin anomaly in rotational nuclear states. The direct consequence of this fact is that the system will make a ''phase transition'' under that situation. Studying the induced rotational asymmetry effect, in the present paper another theoretical fact is discussed, which support this ''phase transition''. Furthermore, it is shown that when this ''phase transition'' occurs, in order to have a proper description of the system, a modification of the physical ground state is necessary which suggests a microscopic theory of band mixing for high spin anomaly in rotational nuclear states

Electric response of Pb0.99[(Zr0.90Sn0.10)0.968Ti0.032]0.98Nb0.02O3 ceramics to the shock-wave-induced ferroelectric-to-antiferroelectric phase transition

International Nuclear Information System (INIS)

Jiang Dongdong; Zhang Na; Feng Yujun; Du Jinmei; Gu Yan

2012-01-01

Highlights: ► Shock wave induces the FE-to-AFE phase transition in PbNb(Zr,Sn,Ti)O 3 . ► Depoling current due to phase transition depends on shock pressure and load resistance. ► Shock pressure promotes the phase transition in short-circuit case. ► Increasing load resistance decreases the released charge. - Abstract: Shock-wave-enforced ferroelectric (FE)-to-antiferroelectric (AFE) phase transition releases a large electrical polarization, having application in pulse power technology. In the present work, the depoling currents under shock wave compression were investigated in Pb 0.99 [(Zr 0.90 Sn 0.10 ) 0.968 Ti 0.032 ] 0.98 Nb 0.02 O 3 (PZST) ceramics with composition close to the FE/AFE phase boundary. Shock wave was generated by gas-gun and propagated in a direction perpendicular to the remanent polarization. It was found that the shock pressure promoted the phase transition under the short-circuit condition. The shock pressure dependence of the released charge was associated with the evolution of FE-to-AFE phase transition. The onset of phase transition was about 0.40 GPa and complete transformation occurred at 1.23 GPa. However, the released charge decreased with increasing load resistance. The reason may be that the electric field suppresses the phase transition in uncompressed zone and/or shock induces conductivity in compressed zone. Results lay the foundation for application of PZST ceramics in shock-activated power supply.

Stochastic resonance induced by the novel random transitions of two-dimensional weak damping bistable duffing oscillator and bifurcation of moment equation

International Nuclear Information System (INIS)

Zhang Guangjun; Xu Jianxue; Wang Jue; Yue Zhifeng; Zou Hailin

2009-01-01

In this paper stochastic resonance induced by the novel random transitions of two-dimensional weak damping bistable Duffing oscillator is analyzed by moment method. This kind of novel transition refers to the one among three potential well on two sides of bifurcation point of original system at the presence of internal noise. Several conclusions are drawn. First, the semi-analytical result of stochastic resonance induced by the novel random transitions of two-dimensional weak damping bistable Duffing oscillator can be obtained, and the semi-analytical result is qualitatively compatible with the one of Monte Carlo simulation. Second, a bifurcation of double-branch fixed point curves occurs in the moment equations with noise intensity as their bifurcation parameter. Third, the bifurcation of moment equations corresponds to stochastic resonance of original system. Finally, the mechanism of stochastic resonance is presented from another viewpoint through analyzing the energy transfer induced by the bifurcation of moment equation.

The difference in noise property between the Autler—Townes splitting medium and the electromagnetically induced transparent medium

International Nuclear Information System (INIS)

Li Zhong-Hua; Li Yuan; Dou Ya-Fang; Zhang Jun-Xiang

2012-01-01

The quantum noise of squeezed probe light passing through an atomic system with different electromagnetically induced transparency and Autler—Townes splitting effects is investigated theoretically. It is found that the optimal squeezing preservation of the outgoing probe beam occurs in the strong-coupling-field regime rather than in the weak-coupling-field regime. In the weak-coupling-field regime, which was recently recognized as the electromagnetically induced transparency regime (Abi-Salloum T Y 2010 Phys. Rev. A 81 053836), the output amplitude noise is affected mainly by the atomic noise originating from the random decay process of atoms. While in the strong-coupling-field regime, defined as the Autler—Townes splitting regime, the output amplitude noise is affected mainly by the phase-to-amplitude conversion noise. This is useful in improving the quality of the experiment for efficient quantum memory, and hence has an application in quantum information processing. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

High-pressure Raman and optical absorption studies on lead pyroniobate (Pb2Nb2O7) and pressure-induced phase transitions

International Nuclear Information System (INIS)

Jayaraman, A.; Kourouklis, G.A.; Cooper, A.S.; Espinosa, G.P.

1990-01-01

High-pressure Raman scattering and optical absorption studies have been carried out on lead pyroniobate (Pb 2 Nb 2 O 7 ) up to 33 GPa, using a gasketed diamond anvil cell. The Raman study reveals the occurrence of two, possibly three, pressure-induced phase changes; a rather subtle change is indicated near 4.5 GPa. The transition near 13 GPa is attributed to a structural transition from the rhombohedral to the cubic pyrochlore structure. The third phase change occurs near 20 GPa. From the broad Raman feature that is observed at about 800 cm -1 , it is concluded that the system turns amorphous at pressures above 20 GPa. The amorphous phase recrystallizes to the original rhombohedral phase, on release of pressure. The broad Raman peaks of the recrystallized phase indicate a high degree of disorder in the material. Lead pyroniobate turns deep red near 30 GPa, from light yellow at ambient pressure. Semi quantitative absorption measurements show that the energy gap shifts red at a rate of 30 meV/GPa. This shift is attributed to the downward motion of the 5d (es) conduction band of Pb

Quantum phase transitions of strongly correlated electron systems

International Nuclear Information System (INIS)

Imada, Masatoshi

1998-01-01

Interacting electrons in solids undergo various quantum phase transitions driven by quantum fluctuations. The quantum transitions take place at zero temperature by changing a parameter to control quantum fluctuations rather than thermal fluctuations. In contrast to classical phase transitions driven by thermal fluctuations, the quantum transitions have many different features where quantum dynamics introduces a source of intrinsic fluctuations tightly connected with spatial correlations and they have been a subject of recent intensive studies as we see below. Interacting electron systems cannot be fully understood without deep analyses of the quantum phase transitions themselves, because they are widely seen and play essential roles in many phenomena. Typical and important examples of the quantum phase transitions include metal-insulator transitions, (2, 3, 4, 5, 6, 7, 8, 9) metal-superconductor transitions, superconductor-insulator transitions, magnetic transitions to antiferromagnetic or ferromagnetic phases in metals as well as in Mott insulators, and charge ordering transitions. Here, we focus on three different types of transitions

Decoherence-induced transition from photon correlation to anti-correlation

International Nuclear Information System (INIS)

Xu, Q

2014-01-01

Decoherence tends to induce the quantum-to-classical transition, which leads to a crucial obstacle in the realization of reliable quantum information processing. Counterintuitively, we propose that the decoherence due to phase decay brings about the switch from photon correlation to anti-correlation. Stronger decoherence also gives rise to an enhancement of the transition from photon correlation to anti-correlation. This breaks the conventional correlation of strong decoherence with fast decorrelation. (letters)

Phase transition study in strongly correlated VO{sub 2} based sensing systems

Energy Technology Data Exchange (ETDEWEB)

Simo, A., E-mail: alinesimo.aline@gmail.com [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Kaviyarasu, K. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Mwakikunga, B. [Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); Madjoe, R. [Physics Department, University of Western Cape, 7535 Belville Cape Town (South Africa); Gibaud, A. [Laboratoire de Physique de l’Etat Condensé, Université du Maine Faculte des sciences, UPRESA 6087, 72085, Le Mans Cedex 9 (France); Maaza, M. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa)

2017-04-15

Highlights: • At 230 °C for about 48 h to prepare successfully VO{sub 2} nanobelts. • 1D shows good sensing performance due to the large active surface of the material. • The good selectivity of methanol compared to acetone and isopropanol. • VOC compounds was observed at room temperature. - Abstract: Intermediate phase monoclinic M2 was observed by inducing in situ X-ray thermo diffraction on VO{sub 2} (M) nanoplatelets. The solid-solid phase transition occurs at around 65 °C assisted with the percolative transition metal-insulator. The existence of an intermediate crystalline phase with room temperature insulator phase and high temperature metallic phase across MIT in VO{sub 2} could be of relevance to understand structural contributions to the phase transition dynamics. In addition, pellet of VO{sub 2} nanostructures have shown to present good sensing properties to various alcohols vapors at room temperature and good selectivity of methanol with 5.54% sensitivity and limit detection below 5 ppm, compared to isopropanol 3.2% and acetone 2.4% respectively.

High temperature-induced phase transitions in Sr2GdRuO6 complex perovskite

International Nuclear Information System (INIS)

Triana, C.A.; Corredor, L.T.; Landínez Téllez, D.A.; Roa-Rojas, J.

2011-01-01

Highlights: ► Crystal structure, thermal expansion and phase transitions at high-temperature of Sr 2 GdRuO 6 perovskite has been investigated. ► X-ray diffraction pattern at 298 K of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with P2 1 /n space group. ► Evolution of X-ray diffraction patterns at high-temperature shows that the Sr 2 GdRuO 6 perovskite suffers two-phase transitions. ► At 573 K the X-ray diffraction pattern of Sr 2 GdRuO 6 corresponds to monoclinic perovskite-type structure with I2/m space group. ► At 1273 K the Sr 2 GdRuO 6 perovskite suffers a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87). -- Abstract: The crystal structure behavior of the Sr 2 GdRuO 6 complex perovskite at high-temperature has been investigated over a wide temperature range between 298 K ≤ T ≤ 1273 K. Measurements of X-ray diffraction at room-temperature and Rietveld analysis of the experimental patterns show that this compound crystallizes in a monoclinic perovskite-like structure, which belongs to the P2 1 /n (no. 14) space group and 1:1 ordered arrangement of Ru 5+ and Gd 3+ cations over the six-coordinate M sites. Experimental lattice parameters were obtained to be a =5.8103(5) Å, b =5.8234(1) Å, c =8.2193(9) Å, V = 278.11(2) Å 3 and angle β = 90.310(5)°. The high-temperature analysis shows the occurrence of two-phase transitions on this material. First, at 573 K it adopts a monoclinic perovskite-type structure with I2/m (no. 12) space group with lattice parameters a = 5.8275(6) Å, b = 5.8326(3) Å, c = 8.2449(2) Å, V = 280.31(3) Å 3 and angle β = 90.251(3)°. Close to 1273 K it undergoes a complete phase-transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87), with lattice parameters a = 5.8726(1) Å, c = 8.3051(4) Å, V = 286.39(8) Å 3 and angle β = 90.0°. The high-temperature phase transition from monoclinic I2/m (no. 12) to tetragonal I4/m (no. 87) is characterized

Phase engineering of monolayer transition-metal dichalcogenide through coupled electron doping and lattice deformation

International Nuclear Information System (INIS)

Ouyang, Bin; Lan, Guoqiang; Song, Jun; Guo, Yinsheng; Mi, Zetian

2015-01-01

First-principles calculations were performed to investigate the phase stability and transition within four monolayer transition-metal dichalcogenide (TMD) systems, i.e., MX 2 (M = Mo or W and X = S or Se) under coupled electron doping and lattice deformation. With the lattice distortion and electron doping density treated as state variables, the energy surfaces of different phases were computed, and the diagrams of energetically preferred phases were constructed. These diagrams assess the competition between different phases and predict conditions of phase transitions for the TMDs considered. The interplay between lattice deformation and electron doping was identified as originating from the deformation induced band shifting and band bending. Based on our findings, a potential design strategy combining an efficient electrolytic gating and a lattice straining to achieve controllable phase engineering in TMD monolayers was demonstrated

Phase transitions in finite systems

Energy Technology Data Exchange (ETDEWEB)

Chomaz, Ph. [Grand Accelerateur National d' Ions Lourds (GANIL), DSM-CEA / IN2P3-CNRS, 14 - Caen (France); Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire

2002-07-01

In this series of lectures we will first review the general theory of phase transition in the framework of information theory and briefly address some of the well known mean field solutions of three dimensional problems. The theory of phase transitions in finite systems will then be discussed, with a special emphasis to the conceptual problems linked to a thermodynamical description for small, short-lived, open systems as metal clusters and data samples coming from nuclear collisions. The concept of negative heat capacity developed in the early seventies in the context of self-gravitating systems will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. Finally a careful study of the thermodynamical limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. (authors)

Phase transitions in finite systems

International Nuclear Information System (INIS)

Chomaz, Ph.; Gulminelli, F.

2002-01-01

In this series of lectures we will first review the general theory of phase transition in the framework of information theory and briefly address some of the well known mean field solutions of three dimensional problems. The theory of phase transitions in finite systems will then be discussed, with a special emphasis to the conceptual problems linked to a thermodynamical description for small, short-lived, open systems as metal clusters and data samples coming from nuclear collisions. The concept of negative heat capacity developed in the early seventies in the context of self-gravitating systems will be reinterpreted in the general framework of convexity anomalies of thermo-statistical potentials. The connection with the distribution of the order parameter will lead us to a definition of first order phase transitions in finite systems based on topology anomalies of the event distribution in the space of observations. Finally a careful study of the thermodynamical limit will provide a bridge with the standard theory of phase transitions and show that in a wide class of physical situations the different statistical ensembles are irreducibly inequivalent. (authors)

Thermoelectric power and phase transitions in lanthanides under pressure up to 20 GPa

International Nuclear Information System (INIS)

Ovsyannikov, Sergey V.; Shchennikov, Vladimir V.; Goshchitskii, Boris N.

2007-01-01

Pressure dependencies of thermopower S of rare-earth metals (Ce and Pr) in a pressure P range of 0-20 GPa and at room temperature are reported. A non-monotonic behaviour of S(P) has been established both at pressure-induced phase transitions: fcc → modified fcc → monoclinic → tetragonal lattice for Ce, and double hexagonal close packed (dhcp) → fcc → modified fcc → monoclinic for Pr. S kept a positive sign for the all high-pressure phases mentioned. Simultaneous measurements of sample contraction have revealed anomalies in the vicinity of the transitions in qualitative agreement with diffraction volumetric data published before. The S(P) dependencies were analysed on the basis of the known results of electronic structure calculation for the Ce and Pr phases. An advantage was demonstrated of the thermopower method in the study of phase transitions and electronic structure of high-pressure phases

Noise-induced chaos and basin erosion in softening Duffing oscillator

International Nuclear Information System (INIS)

Gan Chunbiao

2005-01-01

It is common for many dynamical systems to have two or more attractors coexist and in such cases the basin boundary is fractal. The purpose of this paper is to study the noise-induced chaos and discuss the effect of noises on erosion of safe basin in the softening Duffing oscillator. The Melnikov approach is used to obtain the necessary condition for the rising of chaos, and the largest Lyapunov exponent is computed to identify the chaotic nature of the sample time series from the system. According to the Melnikov condition, the safe basins are simulated for both the deterministic and the stochastic cases of the system. It is shown that the external Gaussian white noise excitation is robust for inducing the chaos, while the external bounded noise is weak. Moreover, the erosion of the safe basin can be aggravated by both the Gaussian white and the bounded noise excitations, and fractal boundary can appear when the system is only excited by the random processes, which means noise-induced chaotic response is induced

Non-equilibrium phase transition

International Nuclear Information System (INIS)

Mottola, E.; Cooper, F.M.; Bishop, A.R.; Habib, S.; Kluger, Y.; Jensen, N.G.

1998-01-01

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Non-equilibrium phase transitions play a central role in a very broad range of scientific areas, ranging from nuclear, particle, and astrophysics to condensed matter physics and the material and biological sciences. The aim of this project was to explore the path to a deeper and more fundamental understanding of the common physical principles underlying the complex real time dynamics of phase transitions. The main emphasis was on the development of general theoretical tools to deal with non-equilibrium processes, and of numerical methods robust enough to capture the time-evolving structures that occur in actual experimental situations. Specific applications to Laboratory multidivisional efforts in relativistic heavy-ion physics (transition to a new phase of nuclear matter consisting of a quark-gluon plasma) and layered high-temperature superconductors (critical currents and flux flow at the National High Magnetic Field Laboratory) were undertaken

Phase Transitions in Mechanically Milled Mn-Al-C Permanent Magnets

Directory of Open Access Journals (Sweden)

Michael J. Lucis

2014-04-01

Full Text Available Mn-Al powders were prepared by rapid solidification followed by high-energy mechanical milling. The rapid solidification resulted in single-phase ε. The milling was performed in both the ε phase and the τ phase, with the τ-phase formation accomplished through a heat treatment at 500 °C for 10 min. For the ε-milled samples, the conversion of the ε to the τ phase was accomplished after milling via the same heat treatment. Mechanical milling induced a significant increase in coercivity in both cases, reaching 4.5 kOe and 4.1 kOe, respectively, followed by a decrease upon further milling. The increase in coercivity was the result of grain refinement induced by the high-energy mechanical milling. Additionally, in both cases a loss in magnetization was observed. Milling in the ε phase showed a smaller decrease in the magnetization due to a higher content of the τ phase. The loss in magnetization was attributed to a stress-induced transition to the equilibrium phases, as no site disorder or oxidation was observed. Surfactant-assisted milling in oleic acid also improved coercivity, but in this case values reached >4 kOe and remained stable at least through 32 h of milling.

Boundary Induced Phase Transition in Cellular Automata Models of Pedestrian Flow

Czech Academy of Sciences Publication Activity Database

Bukáček, M.; Hrabák, Pavel

2016-01-01

Roč. 11, č. 4 (2016), s. 327-338 ISSN 1557-5969 R&D Projects: GA ČR GA13-13502S Institutional support: RVO:67985556 Keywords : Adaptive time-span * Cellular automata model * Floor-field * Pedestrian flow * Phase transition * Principle of bonds Subject RIV: BD - Theory of Information Impact factor: 0.696, year: 2016

Predicting a new phase (T'') of two-dimensional transition metal di-chalcogenides and strain-controlled topological phase transition

Science.gov (United States)

Ma, Fengxian; Gao, Guoping; Jiao, Yalong; Gu, Yuantong; Bilic, Ante; Zhang, Haijun; Chen, Zhongfang; Du, Aijun

2016-02-01

Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities. By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T''), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations. The new T'' MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 0.42 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature. Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2%. Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T'' phase unambiguously display similar band topologies and strain controlled topological phase transitions. Our findings greatly enrich the 2D families of transition metal dichalcogenides and offer a feasible way to control the electronic states of 2D topological insulators for the fabrication of high-speed spintronics devices.Single layered transition metal dichalcogenides have attracted tremendous research interest due to their structural phase diversities. By using a global optimization approach, we have discovered a new phase of transition metal dichalcogenides (labelled as T''), which is confirmed to be energetically, dynamically and kinetically stable by our first-principles calculations. The new T'' MoS2 phase exhibits an intrinsic quantum spin Hall (QSH) effect with a nontrivial gap as large as 0.42 eV, suggesting that a two-dimensional (2D) topological insulator can be achieved at room temperature. Most interestingly, there is a topological phase transition simply driven by a small tensile strain of up to 2%. Furthermore, all the known MX2 (M = Mo or W; X = S, Se or Te) monolayers in the new T'' phase unambiguously display similar band topologies and strain controlled topological

A phase transition close to room temperature in BiFeO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Kreisel, J; Jadhav, P; Chaix-Pluchery, O [Laboratoire des Materiaux et du Genie Physique, Grenoble INP, CNRS, Minatec, 3, parvis Louis Neel, 38016 Grenoble (France); Varela, M [Departamento Fisica Aplicada i Optica, Universitat de Barcelona, Carrer MartI i Franques 1. 08028 Campus UAB, Bellaterra 08193 (Spain); Dix, N; Sanchez, F; Fontcuberta, J, E-mail: jens.kreisel@grenoble-inp.fr [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193 (Spain)

2011-08-31

BiFeO{sub 3} (BFO) multiferroic oxide has a complex phase diagram that can be mapped by using appropriately substrate-induced strain in epitaxial films. By using Raman spectroscopy, we conclusively show that films of the so-called supertetragonal T-BFO phase, stabilized under compressive strain, display a reversible temperature-induced phase transition at about 100 deg. C, and thus close to room temperature. (fast track communication)

Theoretical study of orbital ordering induced structural phase transition in iron pnictides

Energy Technology Data Exchange (ETDEWEB)

Jena, Sushree Sangita, E-mail: sushree@iopb.res.in; Rout, G. C., E-mail: gcr@iopb.res.in [Physics Enclave, Plot No-664/4825, Lane-4A, Shree Vihar, Bhubaneswar-24, Odisha (India); Panda, S. K., E-mail: skp@iopb.res.in

2016-05-06

We attribute the structural phase transition (SPT) in the parent compounds of the iron pnictides to orbital ordering. Due to anisotropy of the d{sub xz} and d{sub yz} orbitals in the xy plane, orbital ordering makes the orthorhombic structure more favorable and thus inducing the SPT. We consider a one band model Hamiltonian consisting of first and second-nearest-neighbor hopping of the electrons. We introduce Jahn-Tellar (JT) distortion in the system arising due to the orbital ordering present in this system. We calculate the electron Green’s function by using Zuvareb’s Green’s function technique and hence calculate an expression for the temperature dependent lattice strain which is computed numerically and self-consistently. The temperature dependent electron specific heat is calculated by minimizing the free energy of the system. The lattice strain is studied by varying the JT coupling and elastic constant of the system. The structural anomaly is studied through the electron occupation number and the specific heat by varying the physical parameters like JT coupling, lattice constant, chemical potential and hopping integrals of the system.

Quark–hadron phase transition in massive gravity

Energy Technology Data Exchange (ETDEWEB)

Atazadeh, K., E-mail: atazadeh@azaruniv.ac.ir

2016-11-15

We study the quark–hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark–hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.

First order electroweak phase transition

International Nuclear Information System (INIS)

Buchmueller, W.; Fodor, Z.

1993-01-01

In this work, the authors have studied the phase transition in the SU(2)gauge theory at finite temperature. The authors' improved perturbative approach does not suffer from the infrared problems appearing in the ordinary loop expansion. The authors have calculated the effective potential up to cubic terms in the couplings. The higher order terms suggest that the method is reliable for Higgs masses smaller than 80 GeV. The authors have obtained a non-vanishing magnetic mass which further weakens the transitions. By use of Langer's theory of metastability, the authors have calculated the nucleation rate for critical bubbles and have discussed some cosmological consequences. For m H <80 GeV the phase transition is first order and proceeds via bubble nucleation and growth. The thin wall approximation is only marginally applicable. Since the phase transition is quite weak SM baryogenesis is unlikely. 8 refs., 5 figs

Dynamics of Rydberg atom lattices in the presence of noise and dissipation

International Nuclear Information System (INIS)

Abdussalam, Wildan

2017-01-01

The work presented in this dissertation concerns dynamics of Rydberg atom lattices in the presence of noise and dissipation. Rydberg atoms possess a number of exaggerated properties, such as a strong van der Waals interaction. The interplay of that interaction, coherent driving and decoherence leads to intriguing non-equilibrium phenomena. Here, we study the non-equilibrium physics of driven atom lattices in the presence of decoherence caused by either laser phase noise or strong decay. In the first case, we compare between global and local noise and explore their effect on the number of excitations and the full counting statistics. We find that both types of noise give rise to a characteristic distribution of the Rydberg excitation number. The main method employed is the Langevin equation but for the sake of efficiency in certain regimes, we use a Markovian master equation and Monte Carlo rate equations, respectively. In the second case, we consider dissipative systems with more general power-law interactions. We determine the phase diagram in the steady state and analyse its generation dynamics using Monte Carlo rate equations. In contrast to nearest-neighbour models, there is no transition to long-range-ordered phases for realistic interactions and resonant driving. Yet, for finite laser detunings, we show that Rydberg atom lattices can undergo a dissipative phase transition to a long-range-ordered antiferromagnetic phase. We identify the advantages of Monte Carlo rate equations over mean field predictions. Having studied the dynamics of Rydberg atom lattices, we study an application of the strong interactions in such systems for quantum information processing. We investigate the coherent exchange of a single photon between a superconducting microwave cavity and a lattice of strongly interacting Rydberg atoms in the presence of local electric field fluctuations plaguing the cavity surface. We show that despite the increased sensitivity of Rydberg states to

Dynamics of Rydberg atom lattices in the presence of noise and dissipation

Energy Technology Data Exchange (ETDEWEB)

Abdussalam, Wildan

2017-08-07

The work presented in this dissertation concerns dynamics of Rydberg atom lattices in the presence of noise and dissipation. Rydberg atoms possess a number of exaggerated properties, such as a strong van der Waals interaction. The interplay of that interaction, coherent driving and decoherence leads to intriguing non-equilibrium phenomena. Here, we study the non-equilibrium physics of driven atom lattices in the presence of decoherence caused by either laser phase noise or strong decay. In the first case, we compare between global and local noise and explore their effect on the number of excitations and the full counting statistics. We find that both types of noise give rise to a characteristic distribution of the Rydberg excitation number. The main method employed is the Langevin equation but for the sake of efficiency in certain regimes, we use a Markovian master equation and Monte Carlo rate equations, respectively. In the second case, we consider dissipative systems with more general power-law interactions. We determine the phase diagram in the steady state and analyse its generation dynamics using Monte Carlo rate equations. In contrast to nearest-neighbour models, there is no transition to long-range-ordered phases for realistic interactions and resonant driving. Yet, for finite laser detunings, we show that Rydberg atom lattices can undergo a dissipative phase transition to a long-range-ordered antiferromagnetic phase. We identify the advantages of Monte Carlo rate equations over mean field predictions. Having studied the dynamics of Rydberg atom lattices, we study an application of the strong interactions in such systems for quantum information processing. We investigate the coherent exchange of a single photon between a superconducting microwave cavity and a lattice of strongly interacting Rydberg atoms in the presence of local electric field fluctuations plaguing the cavity surface. We show that despite the increased sensitivity of Rydberg states to

Electron correlation influenced magnetic phase transitions in f-electron systems

International Nuclear Information System (INIS)

Frauenheim, T.; Ropke, G.

1980-01-01

The temperature-induced phase transition (on lowering the temperature) antiferromagnet-ferromagnet in the heavy rare earth and some of actinide compounds is qualitatively explained in the scope of a two-band Hubbard model and the more complex RKKY model as the result of electron correlation effects in the conduction bands. (orig.)

How to quantify the transition phase during golf swing performance: Torsional load affects low back complaints during the transition phase.

Science.gov (United States)

Sim, Taeyong; Choi, Ahnryul; Lee, Soeun; Mun, Joung Hwan

2017-10-01

The transition phase of a golf swing is considered to be a decisive instant required for a powerful swing. However, at the same time, the low back torsional loads during this phase can have a considerable effect on golf-related low back pain (LBP). Previous efforts to quantify the transition phase were hampered by problems with accuracy due to methodological limitations. In this study, vector-coding technique (VCT) method was proposed as a comprehensive methodology to quantify the precise transition phase and examine low back torsional load. Towards this end, transition phases were assessed using three different methods (VCT, lead hand speed and X-factor stretch) and compared; then, low back torsional load during the transition phase was examined. As a result, the importance of accurate transition phase quantification has been documented. The largest torsional loads were observed in healthy professional golfers (10.23 ± 1.69 N · kg -1 ), followed by professional golfers with a history of LBP (7.93 ± 1.79 N · kg -1 ), healthy amateur golfers (1.79 ± 1.05 N · kg -1 ) and amateur golfers with a history of LBP (0.99 ± 0.87 N · kg -1 ), which order was equal to that of the transition phase magnitudes of each group. These results indicate the relationship between the transition phase and LBP history and the dependency of the torsional load magnitude on the transition phase.

Investigation on phase noise of the signal from a singly resonant optical parametric oscillator

Science.gov (United States)

Jinxia, Feng; Yuanji, Li; Kuanshou, Zhang

2018-04-01

The phase noise of the signal from a singly resonant optical parametric oscillator (SRO) is investigated theoretically and experimentally. An SRO based on periodically poled lithium niobate is built up that generates the signal with a maximum power of 5.2 W at 1.5 µm. The intensity noise of the signal reaches the shot noise level for frequencies above 5 MHz. The phase noise of the signal oscillates depending on the analysis frequency, and there are phase noise peaks above the shot noise level at the peak frequencies. To explain the phase noise feature of the signal, a semi-classical theoretical model of SROs including the guided acoustic wave Brillouin scattering effect within the nonlinear crystal is developed. The theoretical predictions are in good agreement with the experimental results.

Noise-induced hearing loss in small-scale metal industry in Nepal.

Science.gov (United States)

Whittaker, J D; Robinson, T; Acharya, A; Singh, D; Smith, M

2014-10-01

There has been no previous research to demonstrate the risk of noise-induced hearing loss in industry in Nepal. Limited research on occupational noise-induced hearing loss has been conducted within small-scale industry worldwide, despite it being a substantial and growing cause of deafness in the developing world. The study involved a cross-sectional audiometric assessment, with questionnaire-based examinations of noise and occupational history, and workplace noise level assessment. A total of 115 metal workers and 123 hotel workers (control subjects) were recruited. Noise-induced hearing loss prevalence was 30.4 per cent in metal workers and 4.1 per cent in hotel workers, with a significant odds ratio of 10.3. Except for age and time in occupation, none of the demographic factors were significant in predicting outcomes in regression analyses. When adjusted for this finding, and previous noise-exposed occupations, the odds ratio was 13.8. Workplace noise was significantly different between the groups, ranging from 65.3 to 84.7 dBA in metal worker sites, and from 51.4 to 68.6 dBA in the control sites. Metal workers appear to have a greater risk of noise-induced hearing loss than controls. Additional research on occupational noise-induced hearing loss in Nepal and small-scale industry globally is needed.

Shot-noise-limited monitoring and phase locking of the motion of a single trapped ion.

Science.gov (United States)

Bushev, P; Hétet, G; Slodička, L; Rotter, D; Wilson, M A; Schmidt-Kaler, F; Eschner, J; Blatt, R

2013-03-29

We perform a high-resolution real-time readout of the motion of a single trapped and laser-cooled Ba+ ion. By using an interferometric setup, we demonstrate a shot-noise-limited measurement of thermal oscillations with a resolution of 4 times the standard quantum limit. We apply the real-time monitoring for phase control of the ion motion through a feedback loop, suppressing the photon recoil-induced phase diffusion. Because of the spectral narrowing in the phase-locked mode, the coherent ion oscillation is measured with a resolution of about 0.3 times the standard quantum limit.

Field-induced phase transition in a metalorganic spin-dimer system-a potential model system to study Bose-Einstein condensation of magnons

International Nuclear Information System (INIS)

Tsui, Y.; Bruehl, A.; Removic-Langer, K.; Pashchenko, V.; Wolf, B.; Donath, G.; Pikul, A.; Kretz, T.; Lerner, H.-W.; Wagner, M.; Salguero, A.; Saha-Dasgupta, T.; Rahaman, B.; Valenti, R.; Lang, M.

2007-01-01

We report on the results obtained from studying electron spin resonance, magnetic susceptibility, specific heat and thermal expansion experiments on a metalorganic spin-dimer system, C 36 H 48 Cu 2 F 6 N 8 O 12 S 2 (TK91). According to the first principle Density Functional Theory calculations, the compound represents a 3D-coupled dimer system with intradimer coupling J 1 /k B ∼ 10K and interdimer couplings J 2 /k B ∼J 3 /k B ∼ 1K. The measurements have been performed on both pressed powder and single-crystal samples in external magnetic fields up to 12T and at low temperatures down to ∼ 0.2K. Susceptibility measurements reveal a spin-gap behavior consistent with the theoretical results. Furthermore, clear indications of a field-induced phase transition have been observed. A similar field-induced phase transition was also detected in an inorganic compound TlCuCl 3 and was interpreted as Bose-Einstein condensation (BEC) of magnons. The possibility of changing both the intradimer and interdimer couplings in TK91 by chemical substitutions makes the system a potentially good system to study BEC of magnons

Low-complexity linewidth-tolerant time domain sub-symbol optical phase noise suppression in CO-OFDM systems.

Science.gov (United States)

Hong, Xuezhi; Hong, Xiaojian; Zhang, Junwei; He, Sailing

2016-03-07

Two linewidth-tolerant optical phase noise suppression algorithms, non-decision aided sub-symbol optical phase noise suppression (NDA-SPS) and partial-decision aided sub-symbol optical phase noise suppression (PDA-SPS), based on low-complexity time domain sub-symbol processing are proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. High accuracy carrier phase estimation is achieved in the NDA-SPS algorithm without decision error propagation. Compared with NDA-SPS, partial-decision aided estimation is introduced in PDA-SPS to reduce the pilot-overhead by half, yet only a small performance degradation is induced. The principles and computational complexities of the proposed algorithms are theoretically analyzed. By adopting specially designed comb-type pilot subcarriers, multiplier-free observation-based matrix generation is realized in the proposed algorithms. Computationally intensive discrete Fourier transform (DFT) or inverse DFT (IDFT) operations, which are usually carried out in other high-performance inter-carrier-interference (ICI) mitigation algorithms multiple times, are completely avoided. Compared with several other sub-symbol algorithms, the proposed algorithms with lower complexities offer considerably larger laser linewidth tolerances as demonstrated by Monte-Carlo simulations. Numerical analysis verifies that the optimal performance of PDA-SPS can be achieved with moderate numbers of sub-symbols.

Pressure induced phase transition in HfTiO4

International Nuclear Information System (INIS)

Mishra, A.K.; Garg, Nandini; Sharma, Surinder M.; Panneerselvam, G.

2012-01-01

Hafnium titanate is a low thermal expansion ceramic with a very good absorption cross section for thermal neutrons and a high refractoriness, thus making it a desirable nuclear material. At ambient conditions it crystallizes with the orthorhombic structure (space group Pbcn). The material properties of this ceramic have been studied as a function of temperature. However, apart from a lone shock study several decades ago there is no study at static high pressure on this compound. Since this ceramic is used as control rods in nuclear reactors it is important to understand its phase stability at different thermodynamic conditions. Therefore to understand the high pressure behaviour of hafnium titanate we have carried out diamond anvil cell based X-ray diffraction studies up to ∼20 GPa. The studies on this ceramic show that its structure is stable till 11 GPa. However, at ∼11.7 GPa appearance of new diffraction peaks indicate that it undergoes a structural phase transition to a low symmetry structure

Comments on the electroweak phase transition

International Nuclear Information System (INIS)

Dine, M.; Leigh, R.G.; Huet, P.; Linde, A.; Linde, D.

1992-01-01

We report on an investigation of various problems related to the theory of the electroweak phase transition. This includes a determination of the nature of the phase transition, a discussion of the possible role of higher order radiative corrections and the theory of the formation and evolution of the bubbles of the new phase. We find in particular that no dangerous linear terms appear in the effective potential. However, the strength of the first-order phase transition is 2/3 times less than what follows from the one-loop approximation. This rules out baryogenesis in the minimal version of the electroweak theory with light Higgs bosons. (orig.)

A phase transition induces chaos in a predator-prey ecosystem with a dynamic fitness landscape.

Science.gov (United States)

Gilpin, William; Feldman, Marcus W

2017-07-01

In many ecosystems, natural selection can occur quickly enough to influence the population dynamics and thus future selection. This suggests the importance of extending classical population dynamics models to include such eco-evolutionary processes. Here, we describe a predator-prey model in which the prey population growth depends on a prey density-dependent fitness landscape. We show that this two-species ecosystem is capable of exhibiting chaos even in the absence of external environmental variation or noise, and that the onset of chaotic dynamics is the result of the fitness landscape reversibly alternating between epochs of stabilizing and disruptive selection. We draw an analogy between the fitness function and the free energy in statistical mechanics, allowing us to use the physical theory of first-order phase transitions to understand the onset of rapid cycling in the chaotic predator-prey dynamics. We use quantitative techniques to study the relevance of our model to observational studies of complex ecosystems, finding that the evolution-driven chaotic dynamics confer community stability at the "edge of chaos" while creating a wide distribution of opportunities for speciation during epochs of disruptive selection-a potential observable signature of chaotic eco-evolutionary dynamics in experimental studies.

Effect of hyperons on nuclear phase transition

International Nuclear Information System (INIS)

Das, P.; Mallik, S.; Chaudhuri, G.

2016-01-01

Phase transition of nuclear system in heavy ion-collisions at intermediate energy has been studied well for many years and it has also been extended to strange nuclear matter. Recently, using the Canonical Thermodynamical Model (CTM), detailed work on multiplicity distribution of fragments produced from fragmentation of hypernuclear system shows the existence of phase transition or phase coexistence in strange system with Λ-hyperons. In present work we want to continue the investigation on phase transition with respect to some other thermodynamic observables like free energy, specific heat etc. in order to be confirmed about the nature of the transition

The role of solid-solid phase transitions in mantle convection

Science.gov (United States)

Faccenda, Manuele; Dal Zilio, Luca

2017-01-01

With changing pressure and temperature conditions, downwelling and upwelling crustal and mantle rocks experience several solid-solid phase transitions that affect the mineral physical properties owing to structural changes in the crystal lattice and to the absorption or release of latent heat. Variations in density, together with phase boundary deflections related to the non-null reaction slope, generate important buoyancy forces that add to those induced by thermal perturbations. These buoyancy forces are proportional to the density contrast between reactant and product phases, their volume fraction, the slope and the sharpness of the reaction, and affect the style of mantle convection depending on the system composition. In a homogeneous pyrolitic mantle there is little tendency for layered convection, with slabs that may stagnate in the transition zone because of the positive buoyancy caused by post-spinel and post-ilmenite reactions, and hot plumes that are accelerated by phase transformations in the 600-800 km depth range. By adding chemical and mineralogical heterogeneities as on Earth, phase transitions introduce bulk rock and volatiles filtering effects that generate a compositional gradient throughout the entire mantle, with levels that are enriched or depleted in one or more of these components. Phase transitions often lead to mechanical softening or hardening that can be related to a different intrinsic mechanical behaviour and volatile solubility of the product phases, the heating or cooling associated with latent heat, and the transient grain size reduction in downwelling cold material. Strong variations in viscosity would enhance layered mantle convection, causing slab stagnation and plume ponding. At low temperatures and relatively dry conditions, reactions are delayed due to the sluggish kinetics, so that non-equilibrium phase aggregates can persist metastably beyond the equilibrium phase boundary. Survival of low-density metastable olivine

Generalized definitions of phase transitions

International Nuclear Information System (INIS)

Chomaz, Ph.; Gulminelli, F.

2001-09-01

We define a first order phase transition as a bimodality of the event distribution in the space of observations and we show that this is equivalent to a curvature anomaly of the thermodynamical potential and that it implies the Yang Lee behavior of the zeros of the partition sum. Moreover, it allows to study phase transitions out of equilibrium. (authors)

Phase transition and gravitational wave phenomenology of scalar conformal extensions of the Standard Model

Energy Technology Data Exchange (ETDEWEB)

Marzola, Luca; Racioppi, Antonio; Vaskonen, Ville [National Institute of Chemical Physics and Biophysics, Tallinn (Estonia)

2017-07-15

Thermal corrections in classically conformal models typically induce a strong first-order electroweak phase transition, thereby resulting in a stochastic gravitational background that could be detectable at gravitational wave observatories. After reviewing the basics of classically conformal scenarios, in this paper we investigate the phase transition dynamics in a thermal environment and the related gravitational wave phenomenology within the framework of scalar conformal extensions of the Standard Model. We find that minimal extensions involving only one additional scalar field struggle to reproduce the correct phase transition dynamics once thermal corrections are accounted for. Next-to-minimal models, instead, yield the desired electroweak symmetry breaking and typically result in a very strong gravitational wave signal. (orig.)

Pressure induced magneto-structural phase transitions in layered RMn2X2 compounds (invited)

International Nuclear Information System (INIS)

Kennedy, Shane; Wang, Jianli; Campbell, Stewart; Hofmann, Michael; Dou, Shixue

2014-01-01

We have studied a range of pseudo-ternaries derived from the parent compound PrMn 2 Ge 2 , substituting for each constituent element with a smaller one to contract the lattice. This enables us to observe the magneto-elastic transitions that occur as the Mn-Mn nearest neighbour distance is reduced and to assess the role of Pr on the magnetism. Here, we report on the PrMn 2 Ge 2−x Si x , Pr 1−x Y x Mn 2 Ge 2 , and PrMn 2−x Fe x Ge 2 systems. The pressure produced by chemical substitution in these pseudo-ternaries is inherently non-uniform, with local pressure variations dependent on the local atomic distribution. We find that concentrated chemical substitution on the R or X site (e.g., in Pr 0.5 Y 0.5 Mn 2 Ge 2 and PrMn 2 Ge 0.8 Si 1.2 ) can produce a separation into two distinct magnetic phases, canted ferromagnetic and canted antiferromagnetic, with a commensurate phase gap in the crystalline lattice. This phase gap is a consequence of the combination of phase separation and spontaneous magnetostriction, which is positive on transition to the canted ferromagnetic phase and negative on transition to the canted antiferromagnetic phase. Our results show that co-existence of canted ferromagnetic and antiferromagnetic phases depends on chemical pressure from the rare earth and metalloid sites, on local lattice strain distributions and on applied magnetic field. We demonstrate that the effects of chemical pressure bear close resemblance to those of mechanical pressure on the parent compound

Microstructure processes induced by phase transitions in a CuAu alloy as studied by acoustic emission and optical cinematography

Energy Technology Data Exchange (ETDEWEB)

Masek, P.; Chmelik, F.; Sima, V. [Charles Univ., Prague (Czech Republic). Dept. of Metal Physics; Brinck, A.; Neuhaeuser, H. [Technische Univ. Braunschweig (Germany). Inst. fuer Metallphysik und Nukleare Festkoerperphysik

1999-01-15

Combined acoustic emission measurements and surface cinematography observations have been applied to determine the structure evolution during thermal loading of the CuAu alloy. Thermal history and the fashion of thermal loading have been shown to affect considerably the structure response of the CuAu alloy on temperature changes. On thermal loading, intense plastic deformation occurs in certain temperature intervals due to the relaxation of internal stresses induced by phase transitions and structure anisotropy. The main mechanism is twinning taking place most probably in (110) planes. Dislocation glide and grain-boundary sliding have also been observed as minor mechanisms. A shape-restoration effect associated with the order-disorder transition is revealed. Thermal cycling with upper temperatures over 500 C may also result in structural damage.

Antiferrodistortive phase transitions and ground state of PZT ceramics

International Nuclear Information System (INIS)

Pandey, Dhananjai

2013-01-01

The ground state of the technologically important Pb(Zr x Ti (1-x) )O 3 , commonly known as PZT, ceramics is currently under intense debate. The phase diagram of this material shows a morphotropic phase boundary (MPB) for x∼0.52 at 300K, across which a composition induced structural phase transition occurs leading to maximization of the piezoelectric properties. In search for the true ground state of the PZT in the MPB region, Beatrix Noheda and coworkers first discovered a phase transition from tetragonal (space group P4mm) to an M A type monoclinic phase (space group Cm) at low temperatures for x=0.52. Soon afterwards, we discovered yet another low temperature phase transition for the same composition in which the M A type (Cm) monoclinic phase transforms to another monoclinic phase with Cc space group. We have shown that the Cm to Cc phase transition is an antiferrodistortive (AFD) transition involving tilting of oxygen octahedra leading to unit cell doubling and causing appearance of superlattice reflections which are observable in the electron and neutron diffraction patterns only and not in the XRD patterns, as a result of which Noheda and coworkers missed the Cc phase in their synchrotron XRD studies at low temperatures. Our findings were confirmed by leading groups using neutron, TEM, Raman and high pressure diffraction studies. The first principles calculations also confirmed that the true ground state of PZT in the MPB region has Cc space group. However, in the last couple of years, the Cc space group of the ground state has become controversial with an alternative proposal of R3c as the space group of the ground state phase which is proposed to coexist with the metastable Cm phase. In order to resolve this controversy, we recently revisited the issue using pure PZT and 6% Sr 2+ substituted PZT, the latter samples show larger tilt angle on account of the reduction in the average cationic radius at the Pb 2+ site. Using high wavelength neutrons and high

A pressure-induced displacive phase transition in Tris(ethylenediamine) Nickel(II) nitrate

OpenAIRE

Cameron, C.A.; Allan, D.R.; Kamenev, K.V.; Moggach, S.A.; Murrie, M.; Parsons, S.

2014-01-01

[Ni(en)(3)] [NO3](2) undergoes a displacive phase transition from P6(3)22 at ambient pressure to a lower symmetry P6(1)22/P6(5)22 structure between 0.82 and 0.87 GPa, which is characterized by a tripling of the unit cell c-axis and the number of molecules per unit cell. The same transition has been previously observed at 108 K. The application of pressure leads to a general shortening of O H hydrogen bonding interactions in the structure, with the greatest contraction (24%) occurring diagonal...

Quantum percolation phase transition and magnetoelectric dipole glass in hexagonal ferrites

Science.gov (United States)

Rowley, S. E.; Vojta, T.; Jones, A. T.; Guo, W.; Oliveira, J.; Morrison, F. D.; Lindfield, N.; Baggio Saitovitch, E.; Watts, B. E.; Scott, J. F.

2017-07-01

Hexagonal ferrites not only have enormous commercial impact (£2 billion/year in sales) due to applications that include ultrahigh-density memories, credit-card stripes, magnetic bar codes, small motors, and low-loss microwave devices, they also have fascinating magnetic and ferroelectric quantum properties at low temperatures. Here we report the results of tuning the magnetic ordering temperature in PbF e12 -xG axO19 to zero by chemical substitution x . The phase transition boundary is found to vary as TN˜(1-x /xc ) 2 /3 with xc very close to the calculated spin percolation threshold, which we determine by Monte Carlo simulations, indicating that the zero-temperature phase transition is geometrically driven. We find that this produces a form of compositionally tuned, insulating, ferrimagnetic quantum criticality. Close to the zero-temperature phase transition, we observe the emergence of an electric dipole glass induced by magnetoelectric coupling. The strong frequency behavior of the glass freezing temperature Tm has a Vogel-Fulcher dependence with Tm finite, or suppressed below zero in the zero-frequency limit, depending on composition x . These quantum-mechanical properties, along with the multiplicity of low-lying modes near the zero-temperature phase transition, are likely to greatly extend applications of hexaferrites into the realm of quantum and cryogenic technologies.

Noise enhanced stability effect in a metastable system with two different kinds of time delays and cross-correlated noises

International Nuclear Information System (INIS)

Jia Zhenglin; Mei Dongcheng

2011-01-01

We numerically investigate the influences of the time delay τ simultaneously existing in both the deterministic and fluctuating forces, the time delay τ r existing only in the fluctuating force and the cross-correlation strength λ on the enhancement of the mean first-passage time (MFPT) as a function of the additive D and the multiplicative α noise intensities in a metastable system. The results indicate that both the multiplicative and additive noises can induce the noise-enhanced stability (NES) effect. An increase of λ can enhance or weaken the NES effect induced by the additive noise, depending on the value of τ. However, it weakens the NES effect induced by the multiplicative noise with a suppression of the effect of λ caused by increasing τ. The τ-induced critical behavior on both NES effects can be observed, i.e. an increase of τ can enhance or restrain the NES effects induced by the two kinds of noises. With an increase of λ and τ, MFPT versus D shows a transition from one peak to two peaks and finally one peak, implying the multiple NES effect caused by λ and τ. An increase of τ r can enhance the NES effect induced by the additive noise and weaken the NES effect induced by the multiplicative noise.

Phase Transitions on Surfaces. An International Conference. Abstracts and Program, 3-7 August 1981, Orono, Maine.

Science.gov (United States)

1982-04-16

P. J. Estrup Chemisorption-Induced Phase Transitions and Adatom Interactions on GaAs(110) P. Skeath, C. Y. Su, P. W. Chye , I. Lindau and W. E. Spicer...Transitions and Adatom Interactions on GaAs(ll0)* Perry Skeath, C. Y. Su, P. W. Chye , I Lindau, and W. E. Spicer Stanford Electronics Labs Stanford...ORDER PHASE TRANSITIONS* P. KLEBAN and CHIN -KUN HU, Department of Physics and Astronomy and Laboratory for Surface Science and Technology University of

Isotropic-nematic transition in shear flow: State selection, coexistence, phase transitions, and critical behavior

Science.gov (United States)

Olmsted, Peter D.; Goldbart, Paul M.

1992-10-01

Macroscopic fluid motion can have dramatic consequences near the isotropic-nematic transition in fluids of nematogens. We explore some of these consequences using both deterministic and stochastic descriptions involving coupled hydrodynamic equations of motion for the nematic order parameter and fluid velocity fields. By analyzing the deterministic equations of motion we identify the locally stable states of homogeneous nematic order and strain rate, thus determining the homogeneous nonequilibrium steady states which the fluid may adopt. By examining inhomogeneous steady states we construct the analog of a first-order phase boundary, i.e., a line in the nonequilibrium phase diagram spanned by temperature and applied stress, at which nonequilibrium states may coexist, and which terminates in a nonequilibrium analog of a critical point. From an analysis of the nematic order-parameter discontinuity across the coexistence line, along with properties of the interface between homogeneous states, we extract the analog of classical equilibrium critical behavior near the nonequilibrium critical point. We develop a theory of fluctuations about biaxial nonequilibrium steady states by augmenting the deterministic description with noise terms, to simulate the effect of thermal fluctuations. We use this description to discuss the scattering of polarized light by order-parameter fluctuations near the nonequilibrium critical point and also in weak shear flow near the equilibrium phase transition. We find that fluids of nematogens near an appropriate temperature and strain rate exhibit the analog of critical opalescence, the intensity of which is sensitive to the polarizations of the incident and scattered light, and to the precise form of the critical mode.

Microscopic origin of black hole reentrant phase transitions

Science.gov (United States)

Zangeneh, M. Kord; Dehyadegari, A.; Sheykhi, A.; Mann, R. B.

2018-04-01

Understanding the microscopic behavior of the black hole ingredients has been one of the important challenges in black hole physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behavior of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from the large black holes phase to the small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near the large/small transition line differs for usual and reentrant phase transitions. Indeed, for the usual case, the dominant interaction is repulsive whereas for the reentrant case we encounter an attractive interaction. We show that in the reentrant phase transition case, the small black holes behave like a bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

Stochastic resonance: noise-enhanced order

International Nuclear Information System (INIS)

Anishchenko, Vadim S; Neiman, Arkady B; Moss, F; Shimansky-Geier, L

1999-01-01

Stochastic resonance (SR) provides a glaring example of a noise-induced transition in a nonlinear system driven by an information signal and noise simultaneously. In the regime of SR some characteristics of the information signal (amplification factor, signal-to-noise ratio, the degrees of coherence and of order, etc.) at the output of the system are significantly improved at a certain optimal noise level. SR is realized only in nonlinear systems for which a noise-intensity-controlled characteristic time becomes available. In the present review the physical mechanism and methods of theoretical description of SR are briefly discussed. SR features determined by the structure of the information signal, noise statistics and properties of particular systems with SR are studied. A nontrivial phenomenon of stochastic synchronization defined as locking of the instantaneous phase and switching frequency of a bistable system by external periodic force is analyzed in detail. Stochastic synchronization is explored in single and coupled bistable oscillators, including ensembles. The effects of SR and stochastic synchronization of ensembles of stochastic resonators are studied both with and without coupling between the elements. SR is considered in dynamical and nondynamical (threshold) systems. The SR effect is analyzed from the viewpoint of information and entropy characteristics of the signal, which determine the degree of order or self-organization in the system. Applications of the SR concept to explaining the results of a series of biological experiments are discussed. (reviews of topical problems)

Stochastic resonance: noise-enhanced order

Energy Technology Data Exchange (ETDEWEB)

Anishchenko, Vadim S; Neiman, Arkady B [N.G. Chernyshevskii Saratov State University, Saratov (Russian Federation); Moss, F [Department of Physics and Astronomy, University of Missouri at St. Louis (United States); Shimansky-Geier, L [Humboldt University at Berlin (Germany)

1999-01-31

Stochastic resonance (SR) provides a glaring example of a noise-induced transition in a nonlinear system driven by an information signal and noise simultaneously. In the regime of SR some characteristics of the information signal (amplification factor, signal-to-noise ratio, the degrees of coherence and of order, etc.) at the output of the system are significantly improved at a certain optimal noise level. SR is realized only in nonlinear systems for which a noise-intensity-controlled characteristic time becomes available. In the present review the physical mechanism and methods of theoretical description of SR are briefly discussed. SR features determined by the structure of the information signal, noise statistics and properties of particular systems with SR are studied. A nontrivial phenomenon of stochastic synchronization defined as locking of the instantaneous phase and switching frequency of a bistable system by external periodic force is analyzed in detail. Stochastic synchronization is explored in single and coupled bistable oscillators, including ensembles. The effects of SR and stochastic synchronization of ensembles of stochastic resonators are studied both with and without coupling between the elements. SR is considered in dynamical and nondynamical (threshold) systems. The SR effect is analyzed from the viewpoint of information and entropy characteristics of the signal, which determine the degree of order or self-organization in the system. Applications of the SR concept to explaining the results of a series of biological experiments are discussed. (reviews of topical problems)

A LOW-PHASE NOISE FREQUENCY MULTIPLIER CHAIN ...

African Journals Online (AJOL)

operations which are influenced by the development of frequency syn ..... The phase noise of the Isolation amplifier is also measured by .... obtained from manual. T(sec). 100. 1000. 10 ... IEEE Transations on Instrumentation and. Measurement ...

Phase-Transition-Induced Pattern Formation Applied to Basic Research on Homeopathy: A Systematic Review.

Science.gov (United States)

Kokornaczyk, Maria Olga; Scherr, Claudia; Bodrova, Natalia Borisovna; Baumgartner, Stephan

2018-05-16

 Methods based on phase-transition-induced pattern formation (PTPF) are increasingly used in medical research. Frequent application fields are medical diagnosis and basic research in homeopathy. Here, we present a systematic review of experimental studies concerning PTPF-based methods applied to homeopathy research. We also aimed at categorizing the PTPF methods included in this review.  Experimental studies were collected from scientific databases (PubMed, Web of Science, Russian eLibrary) and from experts in the research field in question, following the PRISMA guidelines. The studies were rated according to pre-defined scientific criteria.  The review included 15 experimental studies. We identified seven different PTPF methods applied in 12 experimental models. Among these methods, phase-transition was triggered through evaporation, freezing, or solution, and in most cases led to the formation of crystals. First experimental studies concerning the application of PTPF methods in homeopathic research were performed in the first half of the 20th century; however, they were not continued in the following years. Only in the last decade, different research groups re-launched the idea, introducing new experimental approaches and computerized pattern evaluation techniques. The here-identified PTPF methods are for the first time proposed to be classified as one group of methods based on the same basic physical phenomenon.  Although the number of experimental studies in the area is still rather limited, the long tradition in the application of PTPF methods and the dynamics of the present developments point out the high potential of these methods and indicate that they might meet the demand for scientific methods to study potentized preparations. The Faculty of Homeopathy.

Characteristics of the Current-Controlled Phase Transition of VO2 Microwires for Hybrid Optoelectronic Devices

Directory of Open Access Journals (Sweden)

Arash Joushaghani

2015-08-01

Full Text Available The optical and electrical characteristics of the insulator-metal phase transition of vanadium dioxide (VO2 enable the realization of power-efficient, miniaturized hybrid optoelectronic devices. This work studies the current-controlled, two-step insulator-metal phase transition of VO2 in varying microwire geometries. Geometry-dependent scaling trends extracted from current-voltage measurements show that the first step induced by carrier injection is delocalized over the microwire, while the second, thermally-induced step is localized to a filament about 1 to 2 μm wide for 100 nm-thick sputtered VO2 films on SiO2. These effects are confirmed by direct infrared imaging, which also measures the change in optical absorption in the two steps. The difference between the threshold currents of the two steps increases as the microwires are narrowed. Micron- and sub-micron-wide VO2 structures can be used to separate the two phase transition steps in photonic and electronic devices.

Field-induced valence transition in rare-earth system

International Nuclear Information System (INIS)

Chattopadhaya, A.; Ghatak, S.K.

2000-01-01

The magnetic field-induced valence transition in rare-earth compound has been examined based on a pseudospin S=1 Ising model proposed earlier for valence transition. The model includes finite mixing between two pertinent ionic configurations (magnetic and non-magnetic) separated by an energy gap and with intersite interaction between rare-earth ions. Using the mean field approximation the magnetic behaviour and the critical field (H c ) for transition are obtained as a function of energy gap and temperature. The phase boundary defined in terms of reduced field H c /H co and reduced temperature T/T v (T v being valence transition temperature in absence of field) is nearly independent of energy gap. These results are in qualitative agreement with experimental observation in Yb- and Eu-compounds

Kinetics of quasi-isoenergetic transition processes in biological macromolecules

International Nuclear Information System (INIS)

Petrov, E.G.; Teslenko, V.I.

2010-01-01

A master equation describing the evolution of averaged molecular state occupancies in molecular systems where alternation of molecular energy levels is caused by discrete dichotomous and trichotomous stochastic fields, is derived. This study is focused on the kinetics of quasi-isoenergetic transition processes in the presence of moderately high frequency stochastic field. A novel physical mechanism for temperature-independent transitions in flexible molecular systems is proposed. This mechanism becomes effective when the conformation transitions between quasi-isoenergetic molecular states take place. At room temperatures, stochastic broadening of molecular energy levels predominates the energy of low-frequency vibrations accompanying the transition. This leads to a cancellation of the temperature dependence in the stochastically averaged rate constants. As examples, physical interpretations of the temperature-independent onset of P2X 3 receptor desensitization in neuronal membranes, as well as degradation of PER2 protein in embrionic fibroblasts, are provided.

Kinetics of quasi-isoenergetic transition processes in biological macromolecules

Energy Technology Data Exchange (ETDEWEB)

Petrov, E.G., E-mail: epetrov@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna Street, 14-b, UA-03680 Kiev (Ukraine); Teslenko, V.I. [Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna Street, 14-b, UA-03680 Kiev (Ukraine)

2010-10-05

A master equation describing the evolution of averaged molecular state occupancies in molecular systems where alternation of molecular energy levels is caused by discrete dichotomous and trichotomous stochastic fields, is derived. This study is focused on the kinetics of quasi-isoenergetic transition processes in the presence of moderately high frequency stochastic field. A novel physical mechanism for temperature-independent transitions in flexible molecular systems is proposed. This mechanism becomes effective when the conformation transitions between quasi-isoenergetic molecular states take place. At room temperatures, stochastic broadening of molecular energy levels predominates the energy of low-frequency vibrations accompanying the transition. This leads to a cancellation of the temperature dependence in the stochastically averaged rate constants. As examples, physical interpretations of the temperature-independent onset of P2X{sub 3} receptor desensitization in neuronal membranes, as well as degradation of PER2 protein in embrionic fibroblasts, are provided.

Noise propagation in x-ray phase-contrast imaging and computed tomography

International Nuclear Information System (INIS)

Nesterets, Yakov I; Gureyev, Timur E

2014-01-01

Three phase-retrieval algorithms, based on the transport-of-intensity equation and on the contrast transfer function for propagation-based imaging, and on the linearized geometrical optics approximation for analyser-based imaging, are investigated. The algorithms are compared in terms of their effect on propagation of noise from projection images to the corresponding phase-retrieved images and further to the computed tomography (CT) images/slices of a monomorphous object reconstructed using filtered backprojection algorithm. The comparison is carried out in terms of an integral noise characteristic, the variance, as well as in terms of a simple figure-of-merit, i.e. signal-to-noise ratio per unit dose. A gain factor is introduced that quantitatively characterizes the effect of phase retrieval on the variance of noise in the reconstructed projection images and in the axial slices of the object. Simple analytical expressions are derived for the gain factor and the signal-to-noise ratio, which indicate that the application of phase-retrieval algorithms can increase these parameters by up to two orders of magnitude compared to raw projection images and conventional CT, thus allowing significant improvement in the image quality and/or reduction of the x-ray dose delivered to the patient. (paper)

The quantum phase-transitions of water

Science.gov (United States)

Fillaux, François

2017-08-01

It is shown that hexagonal ices and steam are macroscopically quantum condensates, with continuous spacetime-translation symmetry, whereas liquid water is a quantum fluid with broken time-translation symmetry. Fusion and vaporization are quantum phase-transitions. The heat capacities, the latent heats, the phase-transition temperatures, the critical temperature, the molar volume expansion of ice relative to water, as well as neutron scattering data and dielectric measurements are explained. The phase-transition mechanisms along with the key role of quantum interferences and that of Hartley-Shannon's entropy are enlightened. The notions of chemical bond and force-field are questioned.

Phase transitions in the random field Ising model in the presence of a transverse field

Energy Technology Data Exchange (ETDEWEB)

Dutta, A.; Chakrabarti, B.K. [Saha Institute of Nuclear Physics, Bidhannagar, Calcutta (India); Stinchcombe, R.B. [Saha Institute of Nuclear Physics, Bidhannagar, Calcutta (India); Department of Physics, Oxford (United Kingdom)

1996-09-07

We have studied the phase transition behaviour of the random field Ising model in the presence of a transverse (or tunnelling) field. The mean field phase diagram has been studied in detail, and in particular the nature of the transition induced by the tunnelling (transverse) field at zero temperature. Modified hyper-scaling relation for the zero-temperature transition has been derived using the Suzuki-Trotter formalism and a modified 'Harris criterion'. Mapping of the model to a randomly diluted antiferromagnetic Ising model in uniform longitudinal and transverse field is also given. (author)

Effect of noise-induced nucleation on grain size distribution studied via the phase-field crystal method

International Nuclear Information System (INIS)

Hubert, J; Cheng, M; Emmerich, H

2009-01-01

We contribute to the more detailed understanding of the phase-field crystal model recently developed by Elder et al (2002 Phys. Rev. Lett. 88 245701), by focusing on its noise term and examining its impact on the nucleation rate in a homogeneously solidifying system as well as on successively developing grain size distributions. In this context we show that principally the grain size decreases with increasing noise amplitude, resulting in both a smaller average grain size and a decreased maximum grain size. Despite this general tendency, which we interpret based on Panfilis and Filiponi (2000 J. Appl. Phys. 88 562), we can identify two different regimes in which nucleation and successive initial growth are governed by quite different mechanisms.

Unconventional Topological Phase Transition in Two-Dimensional Systems with Space-Time Inversion Symmetry

Science.gov (United States)

Ahn, Junyeong; Yang, Bohm-Jung

2017-04-01

We study a topological phase transition between a normal insulator and a quantum spin Hall insulator in two-dimensional (2D) systems with time-reversal and twofold rotation symmetries. Contrary to the case of ordinary time-reversal invariant systems, where a direct transition between two insulators is generally predicted, we find that the topological phase transition in systems with an additional twofold rotation symmetry is mediated by an emergent stable 2D Weyl semimetal phase between two insulators. Here the central role is played by the so-called space-time inversion symmetry, the combination of time-reversal and twofold rotation symmetries, which guarantees the quantization of the Berry phase around a 2D Weyl point even in the presence of strong spin-orbit coupling. Pair creation and pair annihilation of Weyl points accompanying partner exchange between different pairs induces a jump of a 2D Z2 topological invariant leading to a topological phase transition. According to our theory, the topological phase transition in HgTe /CdTe quantum well structure is mediated by a stable 2D Weyl semimetal phase because the quantum well, lacking inversion symmetry intrinsically, has twofold rotation about the growth direction. Namely, the HgTe /CdTe quantum well can show 2D Weyl semimetallic behavior within a small but finite interval in the thickness of HgTe layers between a normal insulator and a quantum spin Hall insulator. We also propose that few-layer black phosphorus under perpendicular electric field is another candidate system to observe the unconventional topological phase transition mechanism accompanied by the emerging 2D Weyl semimetal phase protected by space-time inversion symmetry.

Phase transition in SO(3) gauge theory

International Nuclear Information System (INIS)

Datta, Saumen; Gavai, Rajiv V.

1998-01-01

The phase transition in SO(3) lattice gauge theory is investigated by Monte Carlo techniques with a view (i) to understand the relationship between the bulk transition and the deconfinement transition, and (ii) to resolve the current ambiguity about the nature of the high temperature phase. By introduction of a magnetic field, it was shown that the +ve and -ve values of a > correspond to the same phase. Studies on different sized lattices lead to the conclusion that in SO(3), there is only one transition, which is deconfining in nature. (author)

Self-Interference Cancellation Using Time-Domain Phase Noise Estimation in OFDM Full-Duplex Systems

OpenAIRE

Shehata, Heba; Khattab, Tamer

2016-01-01

In full-duplex systems, oscillator phase noise (PN) problem is considered the bottleneck challenge that may face the self-interference cancellation (SIC) stage especially when orthogonal frequency division multiplexing (OFDM) transmission scheme is deployed. Phase noise degrades the SIC performance significantly, if not mitigated before or during the SIC technique. The presence of the oscillator phase noise has different impacts on the transmitted data symbol like common phase error (CPE) and...

What's new with the electroweak phase transition?

CERN Document Server

Laine, M.

1999-01-01

We review the status of non-perturbative lattice studies of the electroweak phase transition. In the Standard Model, the complete phase diagram has been reliably determined, and the conclusion is that there is no phase transition at all for the experimentally allowed Higgs masses. In the Minimal Supersymmetric Standard Model (MSSM), in contrast, there can be a strong first order transition allowing for baryogenesis. Finally, we point out possibilities for future simulations, such as the problem of CP-violation at the MSSM electroweak phase boundary.

Radiation-induced phase transformation in ferromagnetic perovskite

Energy Technology Data Exchange (ETDEWEB)

Podsekin, A K; Dem' yanov, V V; Ivanova, V V; Venevtsev, Yu N [Nauchno-Issledovatel' skij Fiziko-Khimicheskij Inst., Moscow (USSR)

1976-12-01

An effect of neutron irradiation inducing a phase transition in ferromagnetic perovskite, Sr/sub 0.3/La/sub 0.7/MnO/sub 3/, has been discovered and studied. It is shown that a change in the Curie temperature is proportional to the dose of reactor irradiation. A decrease in the temperature of the phase transition with the concentration of radiation defects is accompanied by an increase in the electrical specific resistance and a change in the initial lattice parameters. It is shown that the radiation shift is due to at least two causes, viz. to an increase in the parameters of the elementary cell and the growth of the electrical specific resistance as a result of bounded electron states' forming on the radiation defects.

Microgravity Two-Phase Flow Transition

Science.gov (United States)

Parang, M.; Chao, D.

1999-01-01

Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.

Wilson loop's phase transition probed by non-local observable

Directory of Open Access Journals (Sweden)

Hui-Ling Li

2018-04-01

Full Text Available In order to give further insights into the holographic Van der Waals phase transition, it would be of great interest to investigate the behavior of Wilson loop across the holographic phase transition for a higher dimensional hairy black hole. We offer a possibility to proceed with a numerical calculation in order to discussion on the hairy black hole's phase transition, and show that Wilson loop can serve as a probe to detect a phase structure of the black hole. Furthermore, for a first order phase transition, we calculate numerically the Maxwell's equal area construction; and for a second order phase transition, we also study the critical exponent in order to characterize the Wilson loop's phase transition.

First-principles study of lattice dynamics, structural phase transition, and thermodynamic properties of barium titanate

Energy Technology Data Exchange (ETDEWEB)

Zhang, Huai-Yong; Zhao, Ying-Qin; Lu, Qing [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Zeng, Zhao-Yi [Chongqing Normal Univ. (China). College of Physics and Electronic Engineering; Chinese Academy of Engineering Physics, Mianyang (China). National Key Laboratory for Shock Wave and Detonation Physics Research; Cheng, Yan [Sichuan Univ., Chengdu (China). Inst. of Atomic and Molecular Physics; Sichuan Univ., Chengdu (China). Key Laboratory of High Energy Density Physics and Technology of Ministry of Education

2016-11-01

Lattice dynamics, structural phase transition, and the thermodynamic properties of barium titanate (BaTiO{sub 3}) are investigated by using first-principles calculations within the density functional theory (DFT). It is found that the GGA-WC exchange-correlation functional can produce better results. The imaginary frequencies that indicate structural instability are observed for the cubic, tetragonal, and orthorhombic phases of BaTiO{sub 3} and no imaginary frequencies emerge in the rhombohedral phase. By examining the partial phonon density of states (PDOSs), we find that the main contribution to the imaginary frequencies is the distortions of the perovskite cage (Ti-O). On the basis of the site-symmetry consideration and group theory, we give the comparative phonon symmetry analysis in four phases, which is useful to analyze the role of different atomic displacements in the vibrational modes of different symmetry. The calculated optical phonon frequencies at Γ point for the four phases are in good agreement with other theoretical and experimental data. The pressure-induced phase transition of BaTiO{sub 3} among four phases and the thermodynamic properties of BaTiO{sub 3} in rhombohedral phase have been investigated within the quasi-harmonic approximation (QHA). The sequence of the pressure-induced phase transition is rhombohedral → orthorhombic → tetragonal → cubic, and the corresponding transition pressure is 5.17, 5.92, 6.65 GPa, respectively. At zero pressure, the thermal expansion coefficient α{sub V}, heat capacity C{sub V}, Grueneisen parameter γ, and bulk modulus B of the rhombohedral phase BaTiO{sub 3} are estimated from 0 K to 200 K.

Phase noise analysis of clock recovery based on an optoelectronic phase-locked loop

DEFF Research Database (Denmark)

Zibar, Darko; Mørk, Jesper; Oxenløwe, Leif Katsuo

2007-01-01

A detailed theoretical analysis of a clock-recovery (CR) scheme based on an optoelectronic phase-locked loop is presented. The analysis emphasizes the phase noise performance, taking into account the noise of the input data signal, the local voltage-controlled oscillator (VCO), and the laser....... It is shown that a large loop length results in a higher timing jitter of the recovered clock signal. The impact of the loop length on the clock signal jitter can be reduced by using a low-noise VCO and a low loop filter bandwidth. Using the model, the timing jitter of the recovered optical and electrical...... clock signal can be evaluated. We numerically investigate the timing jitter requirements for combined electrical/optical local oscillators, in order for the recovered clock signal to have less jitter than that of the input signal. The timing jitter requirements for the free-running laser and the VCO...

Dynamic freeze-in: impact of thermal masses and cosmological phase transitions on dark matter production

Science.gov (United States)

Baker, Michael J.; Breitbach, Moritz; Kopp, Joachim; Mittnacht, Lukas

2018-03-01

The cosmological abundance of dark matter can be significantly influenced by the temperature dependence of particle masses and vacuum expectation values. We illustrate this point in three simple freeze-in models. The first one, which we call kinematically induced freeze-in, is based on the observation that the effective mass of a scalar temporarily becomes very small as the scalar potential undergoes a second order phase transition. This opens dark matter production channels that are otherwise forbidden. The second model we consider, dubbed vev-induced freeze-in, is a fermionic Higgs portal scenario. Its scalar sector is augmented compared to the Standard Model by an additional scalar singlet, S, which couples to dark matter and temporarily acquires a vacuum expectation value (a two-step phase transition or "vev flip-flop"). While ≠ 0, the modified coupling structure in the scalar sector implies that dark matter production is significantly enhanced compared to the = 0 phases realised at very early times and again today. The third model, which we call mixing-induced freeze-in, is similar in spirit, but here it is the mixing of dark sector fermions, induced by non-zero , that temporarily boosts the dark matter production rate. For all three scenarios, we carefully dissect the evolution of the dark sector in the early Universe. We compute the DM relic abundance as a function of the model parameters, emphasising the importance of thermal corrections and the proper treatment of phase transitions in the calculation.

Radioactively induced noise in gas-sampling uranium calorimeters

International Nuclear Information System (INIS)

Gordon, H.A.; Rehak, P.

1982-01-01

The signal induced by radioactivity of a U 238 absorber in a cell of a gas-sampling uranium calorimeter was studied. By means of Campbell's theorem, the levels of the radioactively induced noise in uranium gas-sampling calorimeters was calculated. It was shown that in order to obtain similar radioactive noise performance as U-liquid argon or U-scintillator combinations, the α-particles from the uranium must be stopped before entering the sensing volume of gas-uranium calorimeters

Pressure induced structural phase transition in SnS—An ab initio study

Indian Academy of Sciences (India)

Unknown

Abstract. The structural behaviour of SnS under pressure has been investigated by first principle density functional ... tural phase transition from orthorhombic type to monoclinic type structure around 17 GPa which is in good agreement with the ... is achieved by performing the electronic structure and total energy calculation ...

Problem-Solving Phase Transitions During Team Collaboration.

Science.gov (United States)

Wiltshire, Travis J; Butner, Jonathan E; Fiore, Stephen M

2018-01-01

Multiple theories of problem-solving hypothesize that there are distinct qualitative phases exhibited during effective problem-solving. However, limited research has attempted to identify when transitions between phases occur. We integrate theory on collaborative problem-solving (CPS) with dynamical systems theory suggesting that when a system is undergoing a phase transition it should exhibit a peak in entropy and that entropy levels should also relate to team performance. Communications from 40 teams that collaborated on a complex problem were coded for occurrence of problem-solving processes. We applied a sliding window entropy technique to each team's communications and specified criteria for (a) identifying data points that qualify as peaks and (b) determining which peaks were robust. We used multilevel modeling, and provide a qualitative example, to evaluate whether phases exhibit distinct distributions of communication processes. We also tested whether there was a relationship between entropy values at transition points and CPS performance. We found that a proportion of entropy peaks was robust and that the relative occurrence of communication codes varied significantly across phases. Peaks in entropy thus corresponded to qualitative shifts in teams' CPS communications, providing empirical evidence that teams exhibit phase transitions during CPS. Also, lower average levels of entropy at the phase transition points predicted better CPS performance. We specify future directions to improve understanding of phase transitions during CPS, and collaborative cognition, more broadly. Copyright © 2017 Cognitive Science Society, Inc.

Chimera at the phase-flip transition of an ensemble of identical nonlinear oscillators