Critical Digital Tourism Studies

DEFF Research Database (Denmark)

Gyimóthy, Szilvia; Munar, Ana María

2013-01-01

This paper advocates the need for a critical and cross-disciplinary research agenda on the field of digital technologies and tourism. The changing virtual landscape of tourism has received increased attention by tourism scholars. However, contemporary studies on information technologies (IT......) are approached mostly from a business administration perspective and informed by conceptual frameworks developed in management and marketing. IT studies in tourism are still at a stage similar to the first advocacy phase of tourism research in general (Jafari, 1990) and are seldom inspired by relevant...... to studying digital socio-technical systems and virtual mediation in tourism. Critical Digital Tourism Studies opens a new cross-disciplinary field where the sociality of virtual tourism interactions is examined (entailing the study of structures, social rules, ideologies, power relations, sustainability...

Critical current studies of a HTS rectangular coil

Energy Technology Data Exchange (ETDEWEB)

Zhong, Z. [Department of Engineering, University of Cambridge (United Kingdom); Chudy, M., E-mail: Michal.chudy@stuba.sk [Graduate School of Technology Management, University of Pretoria (South Africa); Institute of Power and Applied Electrical Engineering, Slovak University of Technology in Bratislava (Slovakia); Ruiz, H.S. [Department of Engineering, University of Leicester, Leicester LE1 7RH (United Kingdom); Zhang, X.; Coombs, T. [Department of Engineering, University of Cambridge (United Kingdom)

2017-05-15

Highlights: • Unique square pancake coil was manufactured. • Measurements in relatively high magnetic field were performed. • Different sections of the coil were characterized. • Parts of the coil which are limiting critical current were identified. - Abstract: Nowadays, superconducting high field magnets are used in numerous applications due to their superior properties. High temperature superconductors (HTS) are usually used for production of circular pancake or racetrack coils. However different geometries of HTS coils might be required for some specific applications. In this study, the HTS coil wound on a rectangular frame was fully characterized in homogeneous DC background field. The study contains measurements of critical current angular dependencies. The critical current of the entire coil and two selected strands under different magnitudes and orientations of external magnetic fields are measured. The critical regions of the coil in different angular regimes are determined. This study brings better understanding of the in- field performance of HTS coils wound on frames with right-angles.

Being Critical in Marketing Studies

DEFF Research Database (Denmark)

Dholakia, Nikilesh

2012-01-01

review the research spaces for critical studies of marketing in various global settings and conclude that United Kingdom and Nordic Europe have the best epistemic climate, and this region needs to take leadership in promoting greater range of macro and critical studies of marketing in the rest......In this article, I argue that an elevated macro-level perspective is imperative for conducting critical studies in the fields of marketing and consumer research. There are epistemic barriers to operating in this manner, and I offer several suggestions for overcoming these barriers. Finally, I...

Electric field obtained from an elliptic critical-state model for anisotropic type-II superconductors

Energy Technology Data Exchange (ETDEWEB)

Romero-Salazar, C., E-mail: cromeros@ifuap.buap.mx; Hernández-Flores, O.A.

2016-02-15

Highlights: • An anisotropic critical state model that incorporates a non-zero electric field is proposed. • The critical current density is driven by the electric field. • To determinate the magnetic properties is not required a material law for the electric field magnitude. - Abstract: The conventional elliptic critical-state models (ECSM) establish that the electric field vector is zero when it flows a critical current density in a type-II superconductor. This proposal incorporates a finite electric field on the ECSM to study samples with anisotropic-current-carrying capacity. Our theoretical scheme has the advantage of being able to dispense of a material law which drives the electric field magnitude, however, it does not consider the magnetic history of the superconductor.

Upper critical field of Mo-Ni heterostructures

International Nuclear Information System (INIS)

Uher, C.; Watson, W.J.; Cohn, J.L.; Schuller, I.K.

1985-12-01

Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, lambda = 13.8A (disordered structure) and lambda = 16.6A (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 x 10 -13 s and 2 x 10 -13 s, respectively

Critical Metadata for Spectroscopy Field Campaigns

Directory of Open Access Journals (Sweden)

Barbara A. Rasaiah

2014-04-01

Full Text Available A field spectroscopy metadata standard is defined as those data elements that explicitly document the spectroscopy dataset and field protocols, sampling strategies, instrument properties and environmental and logistical variables. Standards for field spectroscopy metadata affect the quality, completeness, reliability, and usability of datasets created in situ. Currently there is no standardized methodology for documentation of in situ spectroscopy data or metadata. This paper presents results of an international experiment comprising a web-based survey and expert panel evaluation that investigated critical metadata in field spectroscopy. The survey participants were a diverse group of scientists experienced in gathering spectroscopy data across a wide range of disciplines. Overall, respondents were in agreement about a core metadataset for generic campaign metadata, allowing for a prioritization of critical metadata elements to be proposed including those relating to viewing geometry, location, general target and sampling properties, illumination, instrument properties, reference standards, calibration, hyperspectral signal properties, atmospheric conditions, and general project details. Consensus was greatest among individual expert groups in specific application domains. The results allow the identification of a core set of metadata fields that enforce long term data storage and serve as a foundation for a metadata standard. This paper is part one in a series about the core elements of a robust and flexible field spectroscopy metadata standard.

Critical Theory and Information Studies: A Marcusean Infusion

Science.gov (United States)

Pyati, Ajit K.

2006-01-01

In the field of library and information science, also known as information studies, critical theory is often not included in debates about the discipline's theoretical foundations. This paper argues that the critical theory of Herbert Marcuse, in particular, has a significant contribution to make to the field of information studies. Marcuse's…

Critical currents and fields of disordered nanocrystalline superconductors

International Nuclear Information System (INIS)

Yavary, H.; Shahzamanian, M.A.; Rabbani, H.

2007-01-01

Full text: There is an enormous effort directed at increasing the upper critical field of the superconducting materials because this upper critical field provides a fundamental limit to the maximum field a magnet system can produce. High-energy particle accelerators and medical resonance imaging body scanners are limited by the for NbTi (10 T). Gigahertz class nuclear-magnetic-resonance and high field laboratory magnets are limited by for Nb 3 Sn (23 T) [1]. However, the values of critical current density are too low for industrial use, possibly because of degraded or nonsuperconducting phases, such as MoS 2 or Mo 2 S 3 , at the grain boundaries or because the pinning site density is not high enough. It has long been known that decreasing the grain size of low-temperature superconducting (LTS) materials, such as Nb 3 Sn, increases the density of flux pinning sites and hence. Nanocrystalline materials are characterized by ultrafine grains and a high density of grain boundaries [2]. Hence nanocrystalline materials can exhibit unusual physical, chemical, and mechanical properties with respect to conventional polycrystalline materials. The purpose of this paper is to investigate the structure of currents and fields in disordered nanocrystalline superconducting materials by the use of quasiclassical many body techniques. The Keldish Greens functions are used to calculate the current density of the system. Since the disorder and microstructure of these nanocrystalline materials are on a sufficiently short length scale as to increase both the density of pinning site and the upper critical field. (authors)

Relativistic reconnection in near critical Schwinger field

Science.gov (United States)

Schoeffler, Kevin; Grismayer, Thomas; Fonseca, Ricardo; Silva, Luis; Uzdensky, Dmitri

2017-10-01

Magnetic reconnection in relativistic pair plasma with QED radiation and pair-creation effects in the presence of strong magnetic fields is investigated using 2D particle-in-cell simulations. The simulations are performed with the QED module of the OSIRIS framework that includes photon emission by electrons and positrons and single photon decay into pairs (non-linear Breit-Wheeler). We investigate the effectiveness of reconnection as a pair- and gamma-ray production mechanism across a broad range of reconnecting magnetic fields, including those approaching the critical quantum (Schwinger) field, and we also explore how the radiative cooling and pair-production processes affect reconnection. We find that in the extreme field regime, the magnetic energy is mostly converted into radiation rather than into particle kinetic energy. This study is a first concrete step towards better understanding of magnetic reconnection as a possible mechanism powering gamma-ray flares in magnetar magnetospheres.

Conformal field theories and critical phenomena

International Nuclear Information System (INIS)

Xu, Bowei

1993-01-01

In this article we present a brief review of the conformal symmetry and the two dimensional conformal quantum field theories. As concrete applications of the conformal theories to the critical phenomena in statistical systems, we calculate the value of central charge and the anomalous scale dimensions of the Z 2 symmetric quantum chain with boundary condition. The results are compatible with the prediction of the conformal field theories

Specific feature of critical fields of inhomogeneous superconducting films

International Nuclear Information System (INIS)

Glazman, L.I.; Dmitrenko, I.M.; Kolin'ko, A.E.; Pokhila, A.S.; Fogel', N.Ya.; Cherkasova, V.G.

1988-01-01

Experimental studies on thin vanadium films (d=250-400 A) have revealed anomaly in the temperature dependence of the upper critical field H cparallel (T), when H is parallel to the sample plane. At certain temperature T 0 the dependence H cparallel 2 (T) has a sharp kink separating two linear portions. The anomalous behaviour of H cparallel (T) of thin V films can be accounted for assuming the film separation into two parallel layers having different parameters (critical temperature T c , coherence length ξ, thickness d). At temperatures above and lower T 0 the dependence H cparallel (T) is mainly dependent on the characteristics of only one layer. The kink in the dependence H cparallel 2 (T) is due to a jump-like transition of the superconducting nucleus from one layer to the other at T c . The anomalous behaviour of the dependence H cparallel (T) is also observed in sandwiches consisting of two identical films separated with a high (about 30 A) dielectric interlayer; however, the transition from one linear portion to the other is smooth. In the case of identical films a specific crossover occurs if at T-T c the critical field H cparallel (T) coinsides with that for the layer of doubled thickness, then at lowering temperature H cparallel (T) asymptotically approaches the critical field of one layer. The calculation within the model described provides a good description for the experimental results

Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films

Energy Technology Data Exchange (ETDEWEB)

Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it

2009-06-24

We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

Random walks, critical phenomena, and triviality in quantum field theory

International Nuclear Information System (INIS)

Fernandez, R.; Froehlich, J.; Sokal, A.D.

1992-01-01

The subject of this book is equilibrium statistical mechanics - in particular the theory of critical phenomena - and quantum field theory. A general review of the theory of critical phenomena in spin systems, field theories, and random-walk and random-surface models is presented. Among the more technical topics treated in this book, the central theme is the use of random-walk representations as a tool to derive correlation inequalities. The consequences of these inequalities for critical-exponent theory and the triviality question in quantum field theory are expounded in detail. The book contains some previously unpublished results. It addresses both the researcher and the graduate student in modern statistical mechanics and quantum field theory. (orig.)

CRITICAL SUCCESS FACTORS FOR BROWN-FIELD CAPITAL AND RENEWAL PROJECTS

Directory of Open Access Journals (Sweden)

J. Warchol

2012-01-01

Full Text Available

ENGLISH ABSTRACT: Manufacturing companies operate in a business environment where incremental growth may be achieved through expansion and renewal of existing plant and facilities. Effective management of the critical success factors of such capital development projects may also provide competitive advantage. These projects tend to be of a brown-field nature, characterised by a significant level of risk arising from the interaction between the project implementation and concurrent operation of the existing physical asset base. So it is vital to understand the factors that influence the success of capital expansion and renewal projects in the brown-field context. Although each project has unique features, there are critical success factors that can be customised for successful outcomes in the brown-field environment. This study identifies five critical success factors applicable to brown-field capital expansion and renewal projects. Managerial focus on the critical factors, and the prospects for successful brown-field projects, are discussed in the paper.

AFRIKAANSE OPSOMMING: Vervaardigers funksioneer in ‘n sakeomgewing waar voortgesette groei bereik word via uitbreiding en hernuwing van bestaande fasiliteite. Die doeltreffende bestuur van kritiese suksesfaktore van sodanige kapitaalprojekte bied geleentheid vir mededingende voordeel. Projekte van hierdie aard neig om geklassifiseer te word as van herontwikkelingsaard, met betekenisvolle gepaardgaande risiko wat voortspruit uit die interaksie tussen projekimplementering en gelyktydige bedryf van bestaande fisiese bates. Derhalwe is dit belangrik om in die konteks van herontwikkeling aandag te gee aan die kritiese faktore wat ‘n rol speel in die bereiking van sukses. Die navorsing identifiseer vyf kritiese suksesfaktore van belang vir uitbreidings- en vernuwingsprojekte.

Magnetic field dependence of the critical superconducting current induced by the proximity effect in silicon

International Nuclear Information System (INIS)

Nishino, T.; Kawabe, U.; Yamada, E.

1986-01-01

The magnetic field dependence of the critical superconducting current induced by the proximity effect in heavily-boron-doped Si is studied experimentally. It is found that the critical current flowing through the p-type-Si-coupled junction decreases with increasing applied magnetic field. The critical current can be expressed as the product of three factors: the current induced by de Gennes's proximity effect, the exponential decrease due to pair breaking by the magnetic field, and the usual diffraction-pattern-like dependence on the magnetic field due to the Josephson effect. The second factor depends on the carrier concentration in the semiconductor. The local critical current shows a rapid decrease at the edge of the electrodes

Critical current degradation in superconducting niobium-titanium alloys in external magnetic fields under loading

International Nuclear Information System (INIS)

Bojko, V.S.; Lazareva, M.B.; Starodubov, Ya.D.; Chernyj, O.V.; Gorbatenko, V.M.

1992-01-01

The effect of external magnetic fields on the stress at which the critical current starts to degrade (the degradation threshold σ 0 e ) under mechanical loads in superconducting Nb-Ti alloys is studied and a possible mechanism of realization of the effect observed is proposed.It is assumed that additional stresses on the transformation dislocation from the external magnetic fields are beneficial for the growth of martensite inclusions whose superconducting parameters (critical current density j k and critical temperature T k ) are lower then those in the initial material.The degradation threshold is studied experimentally in external magnetic fields H up to 7 T.The linear dependence σ 0 e (H) is observed.It is shown that external magnetic fields play an important role in the critical current degradation at the starting stages of deformation.This fact supports the assumption that the degradation of superconducting parameters under loading are due to the phenomenon of superelasticity,i.e. a reversible load-induced change in the martensite inclusions sizes rather than the reversible mechanical twinning.The results obtained are thought to be important to estimating superconducting solenoid stability in a wide range of magnetic fields

The crossover from mean-field to 3D-Ising critical behaviour in a 3-component microemulsion

DEFF Research Database (Denmark)

Seto, H.; Schwahn, D.; Yokoi, E.

1995-01-01

Density fluctuations and associated critical phenomena of water droplets in a water-in-oil microemulsion system have been studied, We have recently found a mean-field behavior in the ''near-critical region'', and this evidence suggested that a crossover from mean-field to non-mean-field behavior...

Critical behavior of mean-field hadronic models for warm nuclear matter

International Nuclear Information System (INIS)

Silva, J.B.; Lourenco, O.; Delfino, A.; Martins, J.S. Sa; Dutra, M.

2008-01-01

We study a set of hadronic mean-field models in the liquid-gas phase transition regime and calculate their critical parameters. The discussion is unified by scaling the coexistence curves in terms of these critical parameters. We study the models close to spinodal points, where they also present critical behavior. Inspired by signals of criticality shown in fragmentation experiments, we analyze two different scenarios in which such behavior would be expected: (i) the stability limits of a metastable system with vanishing external pressure; and (ii) the critical point of a gas-liquid phase equilibrium system for which the Maxwell construction applies. Spinodal and coexistence curves show the regions in which model dependence arises. Unexpectedly, this model dependence does not manifest if one calculates the thermal incompressibility of the models

Dynamical effects and the critical behavior of random-field systems

International Nuclear Information System (INIS)

Shapir, Y.

1985-01-01

A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results. 37 references

Critical fields of niobium nitride films of various granularity

International Nuclear Information System (INIS)

Antonova, E.A.; Sukhov, V.A.

1983-01-01

The behaviour of lattice parameter, specific electrical resistivity, critical temperature, and temperature dependence of upper critical field near Tsub(cr) of sputtered niobium nitride films is investigated versus the substrate temperature and gas mixture composition in the process of reactive cathode sputtering. The relation between extrapolated value of the upper critical field and granularity of niobium nitride films, close as to composition to the stoichiometric one, has been found. Values of the kappa parameter of the Ginsburg-Landau theory and of the coherence length for niobium nitride films of various granularity are estimated in an approximation of uniform distribution of impurities in a sample

Hysteresis, critical fields and superferromagnetism of the film with perpendicular anisotropy

International Nuclear Information System (INIS)

Kalita, V.M.; Kulyk, M.M.; Ryabchenko, S.M.

2016-01-01

This paper is focused on the analysis of hysteresis and critical phenomena of magnetization reversal of superferromagnetic (SFM) state in nanogranular (NG) Co/Al 2 O 3 film with perpendicular anisotropy. It was demonstrated that the transition from the multidomain SFM state to the homogeneous SFM state, during the magnetization process, occurs critically. The value of the field of critical transition to the homogeneous state depends on the demagnetization field, granular anisotropy and interparticle exchange anisotropy. It turned out that the temperature dependence of the coercive force of the film, despite its SFM state, accords with the Neel–Brown formula for anisotropic single-domain ferromagnetic particles, but has an anomalous angular dependence. It was concluded that domain wall motion affects these features of the coercive field. The domain wall movement may occur due to the overturn of magnetic moments of particles in the boundaries between the superdomains. At the same time, the main factors influencing the coercivity are the anisotropy of the particles, which blocks their magnetic moment reorientation, and demagnetizing factor of the film. Together they lead to the anomalous angular dependence of the coercive field. - Highlights: • The transition from the multidomain SFM to homogeneous SFM state occurs critically. • The value of the critical field depends on the direction of the magnetizing field. • Critical transition field depends on the anisotropy of the interparticle exchange. • Dependence of H c (θ H ) differs from expected one for an ensemble of the particles. • Magnetization reversal occurs by turning the particle's moments in domain borders.

Understanding the Role of Critical Incidents in Relation to Self-Efficacy during Course-Embedded Preservice Teacher Field Experiences: A Qualitative Study

Science.gov (United States)

Epperly, Anna C.

2017-01-01

This qualitative, collective case study documented the development of the self-efficacy beliefs of special education preservice candidates during one semester of a course-embedded field experience in a small, private, faith-based university in the Midwest. Interviews of candidates regarding critical incidents in field experiences as documented by…

Critical Point Cancellation in 3D Vector Fields: Robustness and Discussion.

Science.gov (United States)

Skraba, Primoz; Rosen, Paul; Wang, Bei; Chen, Guoning; Bhatia, Harsh; Pascucci, Valerio

2016-02-29

Vector field topology has been successfully applied to represent the structure of steady vector fields. Critical points, one of the essential components of vector field topology, play an important role in describing the complexity of the extracted structure. Simplifying vector fields via critical point cancellation has practical merit for interpreting the behaviors of complex vector fields such as turbulence. However, there is no effective technique that allows direct cancellation of critical points in 3D. This work fills this gap and introduces the first framework to directly cancel pairs or groups of 3D critical points in a hierarchical manner with a guaranteed minimum amount of perturbation based on their robustness, a quantitative measure of their stability. In addition, our framework does not require the extraction of the entire 3D topology, which contains non-trivial separation structures, and thus is computationally effective. Furthermore, our algorithm can remove critical points in any subregion of the domain whose degree is zero and handle complex boundary configurations, making it capable of addressing challenging scenarios that may not be resolved otherwise. We apply our method to synthetic and simulation datasets to demonstrate its effectiveness.

Field induced magnetic quantum critical behavior in the Kondo necklace model

International Nuclear Information System (INIS)

Reyes, Daniel; Continentino, Mucio

2008-01-01

The Kondo necklace model augmented by a Zeeman term, serves as a useful model for heavy fermion compounds in an applied magnetic field. The phase diagram and thermodynamic behavior for arbitrary dimensions d has been investigated previously in the zero field case [D. Reyes, M. Continentino, Phys. Rev. B 76 (2007) 075114. ]. Here we extend the treatment to finite fields using a generalized bond operator representation for the localized and conduction electrons spins. A decoupling scheme on the double time Green's functions yields the dispersion relation for the excitations of the system. Two critical magnetic fields are found namely, a critical magnetic field called henceforth h c1 and a saturation field nominated h c2 . Then three important regions can be investigated: (i) Kondo spin liquid state (KSL) at low fields h c1 ; (ii) destruction of KSL state at h≥h c1 and appearance of a antiferromagnetic state; and (iii) saturated paramagnetic region above the upper critical field h c2

Nucleation of bulk superconductivity close to critical magnetic fields

DEFF Research Database (Denmark)

Fournais, Søren; Kachmar, Ayman

2011-01-01

We consider the two-dimensional Ginzburg–Landau functional with constant applied magnetic field. For applied magnetic fields close to the second critical field HC2 and large Ginzburg–Landau parameter, we provide leading order estimates on the energy of minimizing configurations. We obtain a fine ...

Influence of self-field on the critical current of Bi-2223/Ag tapes

International Nuclear Information System (INIS)

Lehtonen, Jorma; Korpela, Aki; Nah, Wansoo; Kang, Joonsun; Kovac, Pavol; Melisek, Tibor

2004-01-01

The knowledge of critical current density in a superconducting wire is essential in order to compute AC losses. In HTS tapes the critical current density is difficult to estimate from the measured critical current because self-field tends to reduce the current carrying capacity. In this paper the critical current is measured with a single sample and with two similar samples connected in antiparallel in order to compensate the self-field. Both types of measurement are simulated with finite element method. The simulations help to understand the relation between the measured critical current and material properties. The results suggest that in a high quality tape the self-field effect reduced the measured critical current ∼25% if compared to the real critical current at the zero external field

Electric field effect on the critical current of SNS-contact

International Nuclear Information System (INIS)

Rakhmanov, A.L.; Rozhkov, A.V.

1995-01-01

Electric field effect on the SNS-contact critical current is investigated in the Ginzburg-Landau theory approximation. It is shown that the electric field may cause a notable increase of the contact critical current especially if the sample temperature is close to the temperature of a superconducting transition of T sc normal layer. Electric field effect is increased with the reduction of film thickness, but it can strong enough for thick films as well at temperature close to T sc . 11 refs.; 4 figs

High critical magnetic field superconductor La3S4

International Nuclear Information System (INIS)

Westerholt, K.; Bach, H.; Wendemuth, R.; Methfessel, S.

1979-01-01

A report is presented on electrical conductivity, specific heat and magnetization measurements on La 3 S 4 single crystals. The results show that La 3 S 4 is a strong coupling superconductor with a BCS coherence length of 132 A. This extremely low value makes La 3 S 4 an intrinsic high critical magnetic field superconductor with a Landau-Ginsburg parameter of 20. For the temperature gradient of the upper critical magnetic field at the transition temperature values are found up to 35 kG/K. (author)

The upper critical field of CeCoIn5

International Nuclear Information System (INIS)

Howald, Ludovic; Knebel, Georg; Aoki, Dai; Lapertot, Gérard; Brison, Jean-Pascal

2011-01-01

We present a detailed analysis of the upper critical field for CeCoIn 5 under high pressure. We show that, consistent with other measurements, this system shows a decoupling between the maximum of the superconducting transition temperature T c and the maximum pairing strength. We propose a model in which, in order to account for the discrepancy in pressure between the maximum of the upper critical field and the maximum of T c , we introduce magnetic pair-breaking effects, already widely suggested by other measurements. We found that within the Eliashberg frame work, the unusual shape of H c2 (T) can be completely reproduced when magnetic pair breaking is taken into account. Surprisingly, we found that the maximum of pair breaking and of pair coupling coincide in pressure, suggesting that both mechanisms originate from quantum criticality. Our model implies that CeCoIn 5 is the first compound of its family that shows clear decoupling between the maximum of T c and quantum criticality. (paper)

Dynamical effects and the critical behavior of random-field systems (invited)

International Nuclear Information System (INIS)

Shapir, Y.

1985-01-01

A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results

Scalar field critical collapse in 2+1 dimensions

OpenAIRE

Jałmużna, Joanna; Gundlach, Carsten; Chmaj, Tadeusz

2015-01-01

We carry out numerical experiments in the critical collapse of a spherically symmetric massless scalar field in 2+1 spacetime dimensions in the presence of a negative cosmological constant and compare them against a new theoretical model. We approximate the true critical solution as the $n=4$ Garfinkle solution, matched at the lightcone to a Vaidya-like solution, and corrected to leading order for the effect of $\\Lambda

Upper critical field of NbN film

International Nuclear Information System (INIS)

Ashkin, M.; Gavaler, J.R.

1978-01-01

It is proposed and experimentally verified that the anomalously high superconducting critical field normal to the surface of NbN films possessing a column-void microstructure is H/sub c3/, the field appropriate for surface superconductivity. It is also proposed that because the coherence length is much less than the lateral column dimension that the resistivity of the column and not the film enters calculations of the Maki parameter α. A previously noted discrepancy in α is removed by these proposals

Critical behavior in a random field classical Heisenberg model for amorphous systems

International Nuclear Information System (INIS)

Albuquerque, Douglas F. de; Alves, Sandro Roberto L.; Arruda, Alberto S. de

2005-01-01

By using the differential operator technique and the effective field theory scheme, the critical behavior of amorphous classical Heisenberg ferromagnet of spin-1/2 in a random field is studied. The phase diagram in the T-H and T-α planes on a simple cubic lattice for a cluster with two spins is obtained. Tricritical points, reentrant phenomena and influence of the random field and amorphization on the transition temperature are discussed

Effects of small magnetic fields on the critical current of thin films

International Nuclear Information System (INIS)

Passos, Wagner de Assis Cangussu; Lisboa-Filho, Paulo Noronha; Ortiz, Wilson Aires; Kang, W.N.; Choi, Eun-Mi; Hyeong-Jin, Kim; Lee, Sung-Ik Lee

2002-01-01

Full text: Magnetic fields applied perpendicularly to superconducting thin films may produce dendritic patterns, where penetrated and Meissner regions coexist, as observed in Nb, YBaCuO and MgB 2 [1]. A temperature-dependent limiting-field, Hd(T), separates the dendritic mode from a critical-state-like penetration regime. Due to large demagnetizing factors in the perpendicular geometry, small fields may be enough to drive portions of the sample into the mixed state. Lack of symmetry and local defects might then permeate the dendritic mode. Hd(T) is related[2] to the bulk lower critical field, Hc1, which depends on the in-plane current density, J. Not surprisingly, Hd is depressed by J[3]. The dendritic mode can be detected by the AC-susceptibility: penetrated fingers act as intergranular material, and the imaginary component peaks at Tc-inter(J). Films of 0.2-0.4 microns, with millimeter lateral sizes, develop dendrites when submitted to Earth's field[2], what limits the critical current, J c . This contribution studies how J c is affected by field-induced granularity in thin films. 1. C. A. Duran et al., PRB 52 (1995) 75; P. Leiderer et al., PRL. 71 (1993) 2646; T.H. Johansen et al., Supercond. Sci. Technol. 14 (2001) 1. 2. W. A. Ortiz et al., Physica C 361 (2001) 267. 3. A. V. Bobyl et al., cond-mat/0201260, submitted to APL

Perturbative Field-Theoretical Renormalization Group Approach to Driven-Dissipative Bose-Einstein Criticality

Directory of Open Access Journals (Sweden)

Uwe C. Täuber

2014-04-01

Full Text Available The universal critical behavior of the driven-dissipative nonequilibrium Bose-Einstein condensation transition is investigated employing the field-theoretical renormalization group method. Such criticality may be realized in broad ranges of driven open systems on the interface of quantum optics and many-body physics, from exciton-polariton condensates to cold atomic gases. The starting point is a noisy and dissipative Gross-Pitaevski equation corresponding to a complex-valued Landau-Ginzburg functional, which captures the near critical nonequilibrium dynamics, and generalizes model A for classical relaxational dynamics with nonconserved order parameter. We confirm and further develop the physical picture previously established by means of a functional renormalization group study of this system. Complementing this earlier numerical analysis, we analytically compute the static and dynamical critical exponents at the condensation transition to lowest nontrivial order in the dimensional ε expansion about the upper critical dimension d_{c}=4 and establish the emergence of a novel universal scaling exponent associated with the nonequilibrium drive. We also discuss the corresponding situation for a conserved order parameter field, i.e., (subdiffusive model B with complex coefficients.

Non-monotonic field dependence of critical current in composite superconductors

International Nuclear Information System (INIS)

Andrianov, V.V.; Baev, V.P.; Ivanov, S.S.

1982-01-01

The nonmonotonic field dependence of critical current Im(B/sub a/ in composite superconductors is investigated experimentally for current and field varying simultaneously with final rates I and B/sub a/

Magnetic field oscillations of the critical current in long ballistic graphene Josephson junctions

Science.gov (United States)

Rakyta, Péter; Kormányos, Andor; Cserti, József

2016-06-01

We study the Josephson current in long ballistic superconductor-monolayer graphene-superconductor junctions. As a first step, we have developed an efficient computational approach to calculate the Josephson current in tight-binding systems. This approach can be particularly useful in the long-junction limit, which has hitherto attracted less theoretical interest but has recently become experimentally relevant. We use this computational approach to study the dependence of the critical current on the junction geometry, doping level, and an applied perpendicular magnetic field B . In zero magnetic field we find a good qualitative agreement with the recent experiment of M. Ben Shalom et al. [Nat. Phys. 12, 318 (2016), 10.1038/nphys3592] for the length dependence of the critical current. For highly doped samples our numerical calculations show a broad agreement with the results of the quasiclassical formalism. In this case the critical current exhibits Fraunhofer-like oscillations as a function of B . However, for lower doping levels, where the cyclotron orbit becomes comparable to the characteristic geometrical length scales of the system, deviations from the results of the quasiclassical formalism appear. We argue that due to the exceptional tunability and long mean free path of graphene systems a new regime can be explored where geometrical and dynamical effects are equally important to understand the magnetic field dependence of the critical current.

Field modulation of the critical current in magnetic Josephson junctions

International Nuclear Information System (INIS)

Blamire, M G; Smiet, C B; Banerjee, N; Robinson, J W A

2013-01-01

The dependence of the critical current of a simple Josephson junction on the applied magnetic field is well known and, for a rectangular junction, gives rise to the classic ‘Fraunhofer’ modulation with periodic zeros at the fields that introduce a flux quantum into the junction region. Much recent work has been performed on Josephson junctions that contain magnetic layers. The magnetization of such layers introduces additional flux into the junction and, for large junction areas or strong magnetic materials, can significantly distort the modulation of the critical current and strongly suppress the maximum critical current. The growing interest in junctions that induce odd-frequency triplet pairing in a ferromagnet, and the need to make quantitative comparisons with theory, mean that a full understanding of the role of magnetic barriers in controlling the critical current is necessary. This paper analyses the effect of magnetism and various magnetic configurations on Josephson critical currents; the overall treatment applies to junctions of general shape, but the specific cases of square and rectangular junctions are considered. (paper)

Field-induced quantum criticality of a spin-1/2 planar ferromagnet

International Nuclear Information System (INIS)

Mercaldo, M T; Rabuffo, I; Cesare, L De; D'Auria, A Caramico

2009-01-01

The low-temperature critical properties and crossovers of a spin- 1/2 planar ferromagnet in a longitudinal magnetic field are explored in terms of an anisotropic bosonic action, suitable to describe the spin model in the low-temperature regime. This is performed adopting a procedure which combines an averaging over dynamic degrees of freedom and the classical Wilson renormalization group transformation. Within this framework we get the phase boundary, ending in a quantum critical point, and general expressions for the correlation length and susceptibility as functions of the temperature and the applied magnetic field within the disordered phase. In particular, two crossovers occur decreasing the temperature with the magnetic field fixed at its quantum critical point value, which might be actually observable in complex magnetic compounds, as suggested by recent experiments.

Magnetic Field Dependence of the Critical Current in S-N Bilayer Thin Films

Science.gov (United States)

Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen James; Bandler, Simon; Chervenak, James; Kilbourne, Caroline A.; Finkbeiner, Fred M.; Porter, Frederick S.; Kelley, Richard L.; Adams, Joseph S.;

Slow dynamics at critical points: the field-theoretical perspective

International Nuclear Information System (INIS)

Gambassi, Andrea

2006-01-01

The dynamics at a critical point provides a simple instance of slow collective evolution, characterised by aging phenomena and by a violation of the fluctuation-dissipation relation even for long times. By virtue of the universality in critical phenomena it is possible to provide quantitative predictions for some aspects of these behaviours by field-theoretical methods. We review some of the theoretical results that have been obtained in recent years for the relevant (universal) quantities, such as the fluctuation-dissipation ratio, associated with the non-equilibrium critical dynamics

Upper critical field of complex superconducting networks in the continuum limit

International Nuclear Information System (INIS)

Santhanam, P.; Chi, C.C.

1988-01-01

We propose a simple method for calculating the superconducting upper critical field of complex periodic two-dimensional networks in the continuum limit. Two specific lattices with space groups P4gm and C2mm are used to demonstrate this approach. We obtain the result that the ratio of the critical field of these networks to that of a uniform film is close to but larger than 2

Criticality accident studies and research performed in the Valduc criticality laboratory, France

International Nuclear Information System (INIS)

Barbry, F.; Fouillaud, P.

2001-01-01

In 1967, the IPSN (Institut de Protection et de Surete Nucleaire - Nuclear Protection and Safety Institute) started studies and research in France on criticality accidents, with the objective of improving knowledge and modelling of accidents in order to limit consequences to the public, the environment and installations. The criticality accident is accompanied by an intense emission of neutronic and gamma radiation and releases of radioactive products in the form of gas and aerosols, generating irradiation and contamination risks. The main objectives of the studies carried out, particularly using the CRAC installation and the SILENE reactor at Valduc (France), were to model the physics of criticality accidents, to estimate the risks of irradiation and radioactive releases, to elaborate an accident detection system and to provide information for intervention plans. This document summarizes the state of knowledge in the various fields mentioned above. The results of experiments carried out in the Valduc criticality laboratory are used internationally as reference data for the qualification of calculation codes and the assessment of the consequences of a criticality accident. The SILENE installation, that reproduces the various conditions encountered during a criticality accident, is also a unique international research tool for studies and training on those matters. (author)

Matter fields near quantum critical point in (2+1)-dimensional U(1) gauge theory

International Nuclear Information System (INIS)

Liu Guozhu; Li Wei; Cheng Geng

2010-01-01

We study chiral phase transition and confinement of matter fields in (2+1)-dimensional U(1) gauge theory of massless Dirac fermions and scalar bosons. The vanishing scalar boson mass, r=0, defines a quantum critical point between the Higgs phase and the Coulomb phase. We consider only the critical point r=0 and the Coulomb phase with r>0. The Dirac fermion acquires a dynamical mass when its flavor is less than certain critical value N f c , which depends quantitatively on the flavor N b and the scalar boson mass r. When N f f c , the matter fields carrying internal gauge charge are all confined if r≠0 but are deconfined at the quantum critical point r=0. The system has distinct low-energy elementary excitations at the critical point r=0 and in the Coulomb phase with r≠0. We calculate the specific heat and susceptibility of the system at r=0 and r≠0, which can help to detect the quantum critical point and to judge whether dynamical fermion mass generation takes place.

An effective field study of the magnetic properties and critical behaviour at the surface Ising film

International Nuclear Information System (INIS)

Bengrine, M.; Benyoussef, A.; Ez-Zahraouy, H.; Mhirech, F.

1998-09-01

The influence of corrugation and disorder at the surface on the critical behaviour of a ferromagnetic spin-1/2 Ising film is investigated using mean-field theory and finite cluster approximation. It is found that the critical surface exponent β 1 follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent β 1 depends on the concentration p of the strong interaction for p>p c =0,5, while for p≤p c , such critical exponent is independent on the value of p and is equal to the one of the perfect surface. Moreover, in the case of corrugated surface, the effective exponent for a layer z, β eff J(z,n), is calculated as a function of the number of steps at the surface. (author)

Quantum critical point revisited by dynamical mean-field theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Quantum critical point revisited by dynamical mean-field theory

International Nuclear Information System (INIS)

Xu, Wenhu; Kotliar, Gabriel; Rutgers University, Piscataway, NJ; Tsvelik, Alexei M.

2017-01-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields

KAUST Repository

Wang, B.

2013-06-01

Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields

KAUST Repository

Wang, B.; Rosen, P.; Skraba, P.; Bhatia, H.; Pascucci, V.

2013-01-01

Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

Comparative study on the critical current performance of Bi-2223/Ag and YBCO wires in low magnetic fields at liquid nitrogen temperature

International Nuclear Information System (INIS)

Feng, F.; Qu, T.-M.; Gu, C.; Xin, Y.; Gong, W.-Z.; Wu, W.; Han, Z.

2011-01-01

Highlights: → The I c values of Bi-2223/Ag and YBCO wires in low fields at 77 K were compared. → The performance of Bi-2223/Ag in low parallel fields was better than that of YBCO. → The phenomenon mentioned above can be verified by the published literature datum. → A new aspect was brought to understand the transport properties of HTS wires. - Abstract: A comparative study on the critical current performance of Bi-2223/Ag and YBCO coated conductor wires in low magnetic fields at liquid nitrogen temperature was carried out in this work. Five commercial high temperature superconductor wires from different manufacturers were collected. Their critical currents were measured in magnetic fields, ranging from 0 to 0.4 T. On contrary to the common conception, the Bi-2223/Ag samples had better performance than YBCO coated conductor samples in the magnetic fields parallel to the wide surface of superconducting wires within the experimental scope. We also found similar results by collecting the concerned datum from the published literatures to confirm our measurement results. At the present stage, this fact made that the Bi-2223/Ag wires might be the preferred choice for the applications with mainly low parallel fields involved, unless other considerations were prioritized.

Hysteresis of critical currents of superconducting bridges in low perpendicular magnetic fields

International Nuclear Information System (INIS)

Aomine, T.; Tanaka, E.; Yamasaki, S.; Tani, K.; Yonekura, A.

1989-01-01

Hysteresis of critical currents I c of superconducting bridges with In, Nb, and NbN has been studied in low perpendicular magnetic fields. Influences of bridge geometry, small field sweep, trapped flux, and bombardment of argon ions on the hysteresis were made clear. The experimental results suggest that the edge pinning and trapped flux in the bank of bridges are associated with the hysteresis. The peak value of I c of NbN bridges, as well as granular Al and In bridges reported before, in decreasing fields agrees with the calculated pair-breaking current. The origin of the hysteresis is discussed

Isomorphism of critical and off-critical operator spaces in two-dimensional quantum field theory

Energy Technology Data Exchange (ETDEWEB)

Delfino, G. [International School of Advanced Studies (SISSA), Trieste (Italy)]|[INFN sezione di Trieste (Italy); Niccoli, G. [Univ. de Cergy-Pontoise (France). LPTM

2007-12-15

For the simplest quantum field theory originating from a non-trivial fixed point of the renormalization group, the Lee-Yang model, we show that the operator space determined by the particle dynamics in the massive phase and that prescribed by conformal symmetry at criticality coincide. (orig.)

IN SEARCH OF A CRITICAL PSYCHOLOGY IN THE WORK FIELDS

Directory of Open Access Journals (Sweden)

HERNÁN CAMILO PULIDO-MARTÍNEZ

2004-07-01

Full Text Available Critical psychology (Walkerdine, 2001 has not deeply considered the possibilities of construction ofalternative approaches to industrial and organizational psychology. This paper presents research andintervention fields that do not have left aside questions about efficiency but are formulating questionabout why and what for we are organized in certain ways for work. The studies conducted within thediscursive psychology (Parker, 1997, social psychology of organizations Schvarstein (1992, social psychologyof unemployment (Jahoda, 1982, and ideological (Prilleltensky, 1994 and post structuralistcritiques to psychology (Hollway, 1991 are visited. It is point out possible pathways for the constructionof a critical psychology in regards to work. The pertinence of psychological critique and new ways ofresearch and intervention in face of the contemporary work conditions are discussed.

RAPID COMMUNICATION: Effect of strain, magnetic field and field angle on the critical current density of Y Ba2Cu3O7-δ coated conductors

Science.gov (United States)

van der Laan, D. C.; Ekin, J. W.; Douglas, J. F.; Clickner, C. C.; Stauffer, T. C.; Goodrich, L. F.

2010-07-01

A large, magnetic-field-dependent, reversible reduction in critical current density with axial strain in Y Ba2Cu3O7-δ coated conductors at 75.9 K has been measured. This effect may have important implications for the performance of Y Ba2Cu3O7-δ coated conductors in applications where the conductor experiences large stresses in the presence of a magnetic field. Previous studies have been performed only under tensile strain and could provide only a limited understanding of the in-field strain effect. We now have constructed a device for measuring the critical current density as a function of axial compressive and tensile strain and applied magnetic field as well as magnetic field angle, in order to determine the magnitude of this effect and to create a better understanding of its origin. The reversible reduction in critical current density with strain becomes larger with increasing magnetic field at all field angles. At 76 K the critical current density is reduced by about 30% at - 0.5% strain when a magnetic field of 5 T is applied parallel to the c-axis of the conductor or 8 T is applied in the ab-plane, compared to a reduction of only 13% in self-field. Differences in the strain response of the critical current density at various magnetic field angles indicate that the pinning mechanisms in Y Ba2Cu3O7-δ coated conductors are uniquely affected by strain. Contribution of NIST, not subject to US copyright.

Field mapping measurements to determine spatial and field dependence of critical current density in YBCO tapes

International Nuclear Information System (INIS)

Leclerc, J.; Berger, K.; Douine, B.; Lévêque, J.

2013-01-01

Highlights: • A method for characterizing superconducting tapes from field mapping is presented. • A new and efficient field mapping apparatus has been setup. • This method allows the spatial characterization of superconducting tapes. • The critical current density is obtained as a function of the flux density. • This method has been experimentally tested on an YBCO tape. -- Abstract: In this paper a measurement method that allows the determination of the critical current density of superconducting tape from field mapping measurements is presented. This contact-free method allows obtaining characteristics of the superconductor as a function of the position and of the applied flux density. With some modifications, this technique can be used for reel-to-reel measurements. The determination of the critical current density is based on an inverse calculation. This involves calculating the current distribution in the tape from magnetic measurements. An YBaCuO tape has been characterized at 77 K. A defect in this superconductor has been identified. Various tests were carried out to check the efficiency of the method. The inverse calculation was tested theoretically and experimentally. Comparison with a transport current measurement was also performed

Examining Graduate Dissertations in the Field of Critical Thinking: A Case from Turkey

Science.gov (United States)

Demirel, Melek; Derman, Ipek; Can Aran, Ozge

2017-01-01

Purpose: The aim of this study is to conduct content analyses of graduate dissertations about critical thinking skills in the field of educational sciences in Turkey and to document general trends in dissertations. Research Methods: This study is constructed using qualitative research methods and techniques. A document review was used to gather…

Quantum field theory and critical phenomena

CERN Document Server

Zinn-Justin, Jean

1996-01-01

Over the last twenty years quantum field theory has become not only the framework for the discussion of all fundamental interactions except gravity, but also for the understanding of second-order phase transitions in statistical mechanics. This advanced text is based on graduate courses and summer schools given by the author over a number of years. It approaches the subject in terms of path and functional intergrals, adopting a Euclidean metric and using the language of partition and correlation functions. Renormalization and the renormalization group are examined, as are critical phenomena and the role of instantons. Changes for this edition 1. Extensive revision to eliminate a few bugs that had survived the second edition and (mainly) to improve the pedagogical presentation, as a result of experience gathered by lecturing. 2. Additional new topics; holomorphic or coherent state path integral; functional integral and representation of the field theory S-matrix in the holomorphic formalis; non-relativistic li...

Pulsed transport critical currents of Bi2212 tapes in pulsed magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Rogacki, K [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Gilewski, A; Klamut, J [International Laboratory of High Magnetic Fields and Low Temperatures, Polish Academy of Sciences, Wroclaw (Poland); Newson, M; Jones, H [Clarendon Laboratory, University of Oxford, Oxford (United Kingdom); Glowacki, B A [IRC in Superconductivity and Department of Materials Science, University of Cambridge, Cambridge (United Kingdom)

2002-07-01

If high-T{sub C} superconductors are ever to be used in high-field applications, it is vital that the critical surfaces can be mapped under high-field conditions. However, the latest superconductors have high currents even at fields over 20 T, making accurate measurements very difficult due to the thermal and mechanical problems. In this paper, we compare measurements on BSCCO-2212 tape using a number of different methods, particularly an innovative pulsed transport current and pulsed field mode. We show how the analysis of the voltage signal from BSCCO-2212 tape in pulsed conditions may be used to extract the critical current in quasi-stationary conditions. The effect of a metallic substrate on the results is also briefly discussed. (author)

Enhanced upper critical fields in binary Nb-Ti alloys

International Nuclear Information System (INIS)

Hariharan, Y.; Sastry, V.S.; Janawadkar, M.P.; Radhakrishnan, T.S.

1986-01-01

The authors report the enhancement of H/sub c2/ in quenched and suitably heat treated binary Nb-65 at % Ti alloys. The inherent metastability of the bcc β phase and its instability towards athermal ω are used to realise high values of normal state resistivity ε/sub n/. The consequences of this on the upper critical field have been experimentally determined by the measurement of dH/sub c2//dT at T/sub c/ and of T/sub c/. These together with our similar measurements on Nb-83 at % Ti alloy to which at 1 at % N was added (to retain it in the β phase) are analysed in terms of the existing theories for upper critical fields. It is shown that a peak in H/sub c2/(o) occurs at 17 - 18 T when ε/sub n/ has a value of approximately 100 μΩcm

Low field critical currents and ac losses of thin film niobium--tin superconductors

International Nuclear Information System (INIS)

Howard, R.E.

1977-01-01

The results of a study of the low field critical current and ac loss properties of niobium-tin thin films and layered composites fabricated by electron-beam coevaporation are presented. Particular emphasis is placed upon determining the suitability of this material for use as a conductor in a superconducting power transmission line. Chapter I contains a summary of this work and its major results together with an introduction to the scientific and engineering concepts associated with a superconducting power transmission line. Chapter II is a discussion of the physics of current transport and the associated loss mechanisms in a type-II superconductor. Chapter III gives the details of the electron-beam coevaporation technique developed to fabricate the samples for this study. Also discussed in this chapter are the effects of the evaporation conditions on the growth morphology of the niobium-tin films. Chapter IV presents the details of the experimental techniques developed to measure the ac loss and critical current in these samples as a function of temperature. Chapter V shows the dependence of the critical current of these films and composites on temperature, magnetic field, and on the number of artificially introduced pinning centers in the layered composites. Experimental results are also presented concerning the stability of these conductors against flux jumps. Chapter VI is a discussion of the ac losses in these samples. Detailed comparisons are made between the measured loss and the predictions of the critical state model

Conformal field theory and 2D critical phenomena. Part 1

International Nuclear Information System (INIS)

Zamolodchikov, A.B.; Zamolodchikov, Al.B.

1989-01-01

Review of the recent developments in the two-dimensional conformal field theory and especially its applications to the physics of 2D critical phenomena is given. It includes the Ising model, the Potts model. Minimal models, corresponding to theories invariant under higher symmetries, such as superconformal theories, parafermionic theories and theories with current and W-algebras are also discussed. Non-hamiltonian approach to two-dimensional field theory is formulated. 126 refs

Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

Energy Technology Data Exchange (ETDEWEB)

Komar, A.; Pokol, G. I. [Department of Nuclear Techniques, Budapest University of Technology and Economics, Association EURATOM, H-1111 Budapest (Hungary); Fueloep, T. [Department of Applied Physics, Nuclear Engineering, Chalmers University of Technology and Euratom-VR Association, Goeteborg (Sweden)

2013-01-15

Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work, we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case, we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers, and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.

Critical Media and Communication Studies Today. A Conversation

Directory of Open Access Journals (Sweden)

Christian Fuchs

2011-06-01

Full Text Available This article documents a conversation between us that was first published in parallel on our two blogs http://dwmw.wordpress.com and http://fuchs.uti.at/blog. The conversation deals with our assessments of the status of Critical Media and Communication Studies today. We discuss the work of Dallas Smythe, how to study and assess Google, research dimensions of Critical Political Economy of the Media, how important each of these dimensions should be, the role of ideology critique for Critical Political Economy of the Media, the commonalities and differences between Political Economies of the Media and Critical Political Economy of the Media/Critique of the Political Economy of the Media, the role of Karl Marx for Political Economies of the Media, Nicholas Garnham's recent comments on the field of Critical Political Economy of the Media, neoliberalism and capitalist crisis as contexts for Political Economies of the Media. Comments are very welcome on our blogs, URLs to the specific blog postings can be found in the article sections.

Upper critical and irreversibility fields in Ni- and Co-doped pnictide bulk superconductors

Science.gov (United States)

Nikolo, Martin; Singleton, John; Solenov, Dmitry; Jiang, Jianyi; Weiss, Jeremy; Hellstrom, Eric

2018-05-01

A comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe0.95Ni0.05)2As2 (large grain and small grain samples), Ba(Fe0.94Ni0.06)2As2, Ba(Fe0.92Co0.08)2As2, and Ba(Fe0.92Co0.09)2As2 polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T. The full magnetic field-temperature (H-T) phase diagrams, starting at 1.5 K, were measured. The higher temperature, upper critical field Hc2 data are well described by the one-band Werthamer, Helfand, and Hohenberg (WHH) model. At low temperatures, the experimental data depart from the fitted WHH curves, suggesting an emergence of a new phase that could be attributed to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The large values of the Maki fitting parameter α indicate that the Zeeman pair breaking dominates over the orbital pair breaking and spin-paramagnetic pair-breaking effect is significant in these materials. Possible multi-band structure of these materials is lumped into effective parameters of the single-band model. Table of measured physical parameters allows us to compare these pnictide superconductors for different Co- and Ni- doping levels and granularity.

Magnetic field dependence of the critical current density in YBa2Cu3Ox ceramics

International Nuclear Information System (INIS)

Zhukov, A.A.; Moshchalkov, V.V.; Komarkov, D.A.; Shabatin, V.P.; Gordeev, S.N.; Shelomov, D.V.

1989-01-01

Three magnetic field ranges corresponding to different critical current density j c behavior have been found out. They correlate with grain magnetization changes. The inverse critical current density is shown to depend linearly on the sample cross-section due to the magnetic field induced by the flowing current

Quantum Critical Point revisited by the Dynamical Mean Field Theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.

Angular dependence of the upper critical field in Bi2Sr2CuO6+δ

International Nuclear Information System (INIS)

Vedeneev, S.I.; Ovchinnikov, Yu.N.

2002-01-01

The angular dependence of the upper critical field has been investigated in a wide range of temperatures in very high-quality Bi 2 Sr 2 CuO 6+δ single crystals with critical temperature ≅ 9 K in magnetic fields up to 28 T. Although the typical value of the normal state resistivity ratio ≅ 10 4 , the anisotropy ratio of the upper critical fields is much smaller. A model is proposed based on a strong anisotropy and a small transparency between superconducting layers [ru

Theoretical upper critical field Hc2 for inhomogeneous high temperature superconductors

International Nuclear Information System (INIS)

Caixeiro, E.S.; Gonzalez, J.L.; Mello, E.V.L. de

2004-01-01

We present the theoretical upper critical field H c2 (T) of the high temperature superconductors (HTSC), calculated through a linearized Ginzburg-Landau equation modified to consider the intrinsic inhomogeneity of the HTSC. The unusual behavior of H c2 (T) for these compounds, and other properties like the Meissner and Nernst effects detected at temperatures much higher than the critical temperature T c of the sample, are explained by the approach

Static Magnetic Field Therapy: A Critical Review of Treatment Parameters

Directory of Open Access Journals (Sweden)

Agatha P. Colbert

2009-01-01

Full Text Available Static magnetic field (SMF therapy, applied via a permanent magnet attached to the skin, is used by people worldwide for self-care. Despite a lack of established SMF dosage and treatment regimens, multiple studies are conducted to evaluate SMF therapy effectiveness. Our objectives in conducting this review are to: (i summarize SMF research conducted in humans; (ii critically evaluate reporting quality of SMF dosages and treatment parameters and (iii propose a set of criteria for reporting SMF treatment parameters in future clinical trials. We searched 27 electronic databases and reference lists. Only English language human studies were included. Excluded were studies of electromagnetic fields, transcranial magnetic stimulation, magnets placed on acupuncture points, animal studies, abstracts, posters and editorials. Data were extracted on clinical indication, study design and 10 essential SMF parameters. Three reviewers assessed quality of reporting and calculated a quality assessment score for each of the 10 treatment parameters. Fifty-six studies were reviewed, 42 conducted in patient populations and 14 in healthy volunteers. The SMF treatment parameters most often and most completely described were site of application, magnet support device and frequency and duration of application. Least often and least completely described were characteristics of the SMF: magnet dimensions, measured field strength and estimated distance of the magnet from the target tissue. Thirty-four (61% of studies failed to provide enough detail about SMF dosage to permit protocol replication by other investigators. Our findings highlight the need to optimize SMF dosing parameters for individual clinical conditions before proceeding to a full-scale clinical trial.

Critical Kinship Studies

DEFF Research Database (Denmark)

In recent decades the concept of kinship has been challenged and reinvigorated by the so-called “repatriation of anthropology” and by the influence of feminist studies, queer studies, adoption studies, and science and technology studies. These interdisciplinary approaches have been further...... developed by increases in infertility, reproductive travel, and the emergence of critical movements among transnational adoptees, all of which have served to question how kinship is now practiced. Critical Kinship Studies brings together theoretical and disciplinary perspectives and analytically sensitive...... in the Humanities and Social Sciences today. Critical Kinship Studies should be of particular interest to students and scholars in Anthropology, Sociology, Cultural Studies, Medical Humanities, Politics, Gender and Queer Studies and Globalization....

Acute enhancement of the upper critical field for superconductivity approaching a quantum critical point in URhGe

Energy Technology Data Exchange (ETDEWEB)

Levy, F; Huxley, A [CEA, SPSMS, DRFMC, F-38054 Grenoble, (France); Levy, F; Sheikin, I [CNRS, GHMFL, F-38042 Grenoble, (France); Huxley, A [Univ Edinburgh, Scottish Univ Phys Alliance, Sch Phys, Edinburgh EH9 3JZ, Midlothian, (United Kingdom)

2007-07-01

When a pure material is tuned to the point where a continuous phase-transition line is crossed at zero temperature, known as a quantum critical point (QCP), completely new correlated quantum ordered states can form. These phases include exotic forms of superconductivity. However, as superconductivity is generally suppressed by a magnetic field, the formation of superconductivity ought not to be possible at extremely high field. Here, we report that as we tune the ferromagnet, URhGe, towards a QCP by applying a component of magnetic field in the material's easy magnetic plane, superconductivity survives in progressively higher fields applied simultaneously along the material's magnetic hard axis. Thus, although superconductivity never occurs above a temperature of 0.5 K, we find that it can survive in extremely high magnetic fields, exceeding 28 T. (authors)

Lower critical field of an anisotropic type-II superconductor

International Nuclear Information System (INIS)

Klemm, R.A.; Clem, J.R.

1980-01-01

We consider the Ginzburg-Landau free energy of the anisotropic mass form in the presence of a magnetic field of arbitrary fixed direction. It is shown that the free energy may be transformed into the isotropic Ginsburg-Landau form with a kappa that depends upon the direction of the magnetic induction B relative to the crystal lattice. The lower critical field H/sub c/1 is then found for arbitrary direction of B. For highly anisotropic crystals the angular dependence of H/sub c/1 can exhibit a discontinuity or a cusp. The special case of a crystal with uniaxial symmetry is considered in detail

Stochastic geometry of critical curves, Schramm-Loewner evolutions and conformal field theory

International Nuclear Information System (INIS)

Gruzberg, Ilya A

2006-01-01

Conformally invariant curves that appear at critical points in two-dimensional statistical mechanics systems and their fractal geometry have received a lot of attention in recent years. On the one hand, Schramm (2000 Israel J. Math. 118 221 (Preprint math.PR/9904022)) has invented a new rigorous as well as practical calculational approach to critical curves, based on a beautiful unification of conformal maps and stochastic processes, and by now known as Schramm-Loewner evolution (SLE). On the other hand, Duplantier (2000 Phys. Rev. Lett. 84 1363; Fractal Geometry and Applications: A Jubilee of Benot Mandelbrot: Part 2 (Proc. Symp. Pure Math. vol 72) (Providence, RI: American Mathematical Society) p 365 (Preprint math-ph/0303034)) has applied boundary quantum gravity methods to calculate exact multifractal exponents associated with critical curves. In the first part of this paper, I provide a pedagogical introduction to SLE. I present mathematical facts from the theory of conformal maps and stochastic processes related to SLE. Then I review basic properties of SLE and provide practical derivation of various interesting quantities related to critical curves, including fractal dimensions and crossing probabilities. The second part of the paper is devoted to a way of describing critical curves using boundary conformal field theory (CFT) in the so-called Coulomb gas formalism. This description provides an alternative (to quantum gravity) way of obtaining the multifractal spectrum of critical curves using only traditional methods of CFT based on free bosonic fields

Critical study of the dispersive n- 90Zr mean field by means of a new variational method

Science.gov (United States)

Mahaux, C.; Sartor, R.

1994-02-01

A new variational method is developed for the construction of the dispersive nucleon-nucleus mean field at negative and positive energies. Like the variational moment approach that we had previously proposed, the new method only uses phenomenological optical-model potentials as input. It is simpler and more flexible than the previous approach. It is applied to a critical investigation of the n- 90Zr mean field between -25 and +25 MeV. This system is of particular interest because conflicting results had recently been obtained by two different groups. While the imaginary parts of the phenomenological optical-model potentials provided by these two groups are similar, their real parts are quite different. Nevertheless, we demonstrate that these two sets of phenomenological optical-model potentials are both compatible with the dispersion relation which connects the real and imaginary parts of the mean field. Previous hints to the contrary, by one of the two other groups, are shown to be due to unjustified approximations. A striking outcome of the present study is that it is important to explicitly introduce volume absorption in the dispersion relation, although volume absorption is negligible in the energy domain investigated here. Because of the existence of two sets of phenomenological optical-model potentials, our variational method yields two dispersive mean fields whose real parts are quite different at small or negative energies. No preference for one of the two dispersive mean fields can be expressed on purely empirical grounds since they both yield fair agreement with the experimental cross sections as well as with the observed energies of the bound single-particle states. However, we argue that one of these two mean fields is physically more meaningful, because the radial shape of its Hartree-Fock type component is independent of energy, as expected on theoretical grounds. This preferred mean field is very close to the one which had been obtained by the Ohio

Determination of low-field critical parameters of superconducting niobium by small-angle neutron diffraction

International Nuclear Information System (INIS)

Christen, D.K.; Spooner, S.; Thorel, P.; Kerchner, H.R.

1977-01-01

The perfect double-crystal small-angle diffraction technique enables measurement of scattering angles to within 0.3 arc sec. accuracy. At a wavelength of 2.55 A, this provides a resolution of 3 x 10 -6 A -1 in the scattering vector. This technique has been used to study the anisotropic behavior of the critical parameters B 0 and H/sub c1/, characteristic of the first-order magnetic phase transition which occurs in low-kappa type-II superconductors. Magnetic fields were applied parallel to several crystal axes of a large single-crystal sphere of pure niobium, resulting in well-defined flux-line lattices (FLL). Measurement of the FLL cell area in the intermediate mixed state field region gives the equilibrium flux density B 0 , which results from an attractive interaction between fluxoids. In addition, field variation of the scattered neutron intensity allows measurement of the transition field between the mixed state and intermediate mixed state. This transition field is related to the lower critical field H/sub c1/ and enables its determination to a precision 0.2%. Data at T = 4.3 K display a small anisotropic effect of about 2% in B 0 and 1% in H/sub c1/. Although orientation effects of this magnitude are difficult to resolve by bulk measurements, the neutron data are in accord with magnetization data. Observations regarding the temperature dependence of these parameters also will be presented, and comparisons made with current theoretical models

Response of hard superconductors to crossed magnetic fields: elliptic critical-state model

Energy Technology Data Exchange (ETDEWEB)

Romero-Salazar, C.; Perez-Rodriguez, F

2004-05-01

The behavior of hard superconductors subjected to crossed magnetic fields is theoretically investigated by employing an elliptic critical-state model. Here the anisotropy is induced by flux-line cutting. The model reproduces successfully the collapse of the magnetic moment under the action of a sweeping magnetic field, applied perpendicularly to a dc field, for diamagnetic and paramagnetic initial states. Besides, it explains the transition from the diamagnetic state to the paramagnetic one when the magnitudes of the crossed magnetic fields are of the same order.

When Sex and Power Collide: An Argument for Critical Sexuality Studies.

Science.gov (United States)

Fahs, Breanne; McClelland, Sara I

2016-01-01

Attentive to the collision of sex and power, we add momentum to the ongoing development of the subfield of critical sexuality studies. We argue that this body of work is defined by its critical orientation toward the study of sexuality, along with a clear allegiance to critical modalities of thought, particularly feminist thought. Critical sexuality studies takes its cues from several other critical moments in related fields, including critical psychology, critical race theory, critical public health, and critical youth studies. Across these varied critical stances is a shared investment in examining how power and privilege operate, understanding the role of historical and epistemological violence in research, and generating new models and paradigms to guide empirical and theoretical research. With this guiding framework, we propose three central characteristics of critical sexuality studies: (a) conceptual analysis, with particular attention to how we define key terms and conceptually organize our research (e.g., attraction, sexually active, consent, agency, embodiment, sexual subjectivity); (b) attention to the material qualities of abject bodies, particularly bodies that are ignored, overlooked, or pushed out of bounds (e.g., viscous bodies, fat bodies, bodies in pain); and (c) heteronormativity and heterosexual privilege, particularly how assumptions about heterosexuality and heteronormativity circulate in sexuality research. Through these three critical practices, we argue that critical sexuality studies showcases how sex and power collide and recognizes (and tries to subvert) the various power imbalances that are deployed and replicated in sex research.

The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory

International Nuclear Information System (INIS)

Kiskis, J.; Narayanan, R.; Vranas, P.

1993-01-01

The authors study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments, the authors show that the critical exponent v describing the vanishing of the physical mass at the critical point is equal to v θ /d w , where d w is the Hausdorff dimension of the walk, and v θ = var-phi, where var-phi is the crossover exponent known in the context of field theory. This implies that the Hausdorff dimension of the walk is var-phi/v for O(N) models. 3 refs

Critical studies in international business: a dialog proposal

Directory of Open Access Journals (Sweden)

Nicole Spohr

2013-11-01

Full Text Available Although the area known as International Business (IB is growing in Brazil and in the world, research in this field has been dominated by functionalist approaches and tends to ignore issues of power. Furthermore, the area has adopted Anglo-American references acritically, which suggests an epistemic colonialism. Thus, the aim of this paper is to suggest a critical approach as a way of conducting research in this area. Thus, we will recount the origins of the field, its resistance to the adoption of critical approaches and/or reflective, and seek denaturalised this area to propose a decolonization as an alternative to the field.

The behavior of the critical current density below and above the first matching field in superconductors with periodic square arrays of pinning sites

International Nuclear Information System (INIS)

Obaidat, I.M.; Al Khawaja, U.; Benkraouda, M.; Salmeen, N.

2006-01-01

We have studied the effect of the applied magnetic field on critical depinning force at zero and finite temperatures and for several values of pinning strength. This was achieved by conducting extensive series of molecular dynamic simulations on driven vortex lattices interacting with periodic square arrays of pinning sites. We have found that the critical depinning force decreases as the applied magnetic field is increased. We have also observed two distinct behaviors of dependence of the critical depinning force on the applied magnetic field below and above the first matching filed

Field-dependent transport critical current in single crystals of Ba(Fe1-xTMx)2As2 (TM = Co, Ni) superconductors

International Nuclear Information System (INIS)

Tanatar, M A; Ni, N; Bud'ko, S L; Canfield, P C; Prozorov, R

2010-01-01

Critical current density was studied by direct electrical transport measurements in single crystals of Ba(Fe 1-x TM x ) 2 As 2 under magnetic fields up to 9 T. To understand the relation of the critical current to the structural transformations in the material, the electron doping level was controlled by the amount of TM = Co (underdoped x = 0.054 versus optimally doped x = 0.074) and by the nature of the dopant (optimally doped TM = Co versus TM = Ni). It is found that the suppression of the critical current density by the magnetic field is much slower for Ni and underdoped Co compositions than for an optimally doped Co composition. We relate this difference to the proximity to the orthorhombic/antiferromagnetic phase boundary in the T(x) phase diagram. Structural domains formed in this area of the phase diagram create favorable conditions for pinning and not only increase critical current densities, but also hamper the degradation of the critical current under magnetic field.

Paramagnetic limiting of the upper critical field of the layered organic superconductor κ-(BEDT-TTF)2Cu(SCN)2

International Nuclear Information System (INIS)

Zuo, F.; Brooks, J.S.; McKenzie, R.H.; Schlueter, J.A.; Williams, J.M.

2000-01-01

We report detailed measurements of the interlayer magnetoresistance of the layered organic superconductor κ-(BEDT-TTF) 2 Cu(SCN) 2 for temperatures down to 0.5 K and fields up to 30 T. The upper critical field is determined from the resistive transition for a wide range of temperatures and field directions. For magnetic fields parallel to the layers, the upper critical field increases approximately linearly with decreasing temperature. The upper critical field at low temperatures is compared to the Pauli paramagnetic limit, at which singlet superconductivity should be destroyed by the Zeeman splitting of the electron spins. The measured value is comparable to a value for the paramagnetic limit calculated from thermodynamic quantities but exceeds the limit calculated from BCS theory. The angular dependence of the upper critical field shows a cusplike feature for fields close to the layers, consistent with decoupled layers.

Theory of the upper critical field in layered superconductors

International Nuclear Information System (INIS)

Klemm, R.A.; Luther, A.; Beasley, M.R.

1975-01-01

The upper critical field H/subc/ 2 in layered superconductors is calculated from a microscopic theory in which the electrons are assumed to propagate freely within the individual layers subject to scattering off impurities and to propagate via tunneling between the layers. For the magnetic field parallel to the layers, there is a temperature T* 2 /sub parallel/ is thus determined by the combined effects of Pauli paramagnetism and spin-orbit scattering, and for sufficiently strong spin-orbit scattering rates, H/subc/ 2 /sub parallel/(T =0) can greatly exceed the Chandrasekhar-Clogston Pauli limiting field H/subP/. This unusual behavior is found to be most pronounced in the dirty limit for the electron propagation within the layers and when the electrons scatter many times in a given layer before tunneling to an adjacent layer. Our results are also discussed in light of the available experimental data. (auth)

Virtual-site correlation mean field approach to criticality in spin systems

International Nuclear Information System (INIS)

Sen, Aditi; Sen, Ujjwal

2013-01-01

We propose a virtual-site correlation mean field theory for dealing with interacting many-body systems. It involves a coarse-graining technique that terminates a step before the mean field theory: While mean field theory deals with only single-body physical parameters, the virtual-site correlation mean field theory deals with single- as well as two-body ones, and involves a virtual site for every interaction term in the Hamiltonian. We generalize the theory to a cluster virtual-site correlation mean field, that works with a fundamental unit of the lattice of the many-body system. We apply these methods to interacting Ising spin systems in several lattice geometries and dimensions, and show that the predictions of the onset of criticality of these models are generally much better in the proposed theories as compared to the corresponding ones in mean field theories

Angular and magnetic field dependences of critical current in irradiated YBaCuO single crystals

International Nuclear Information System (INIS)

Petrusenko, Yu.

2010-01-01

The investigation of mechanisms responsible for the current-carrying capability of irradiated high-temperature superconductors (HTSC) was realized. For the purpose, experiments were made to investigate the effect of point defects generated by high-energy electron irradiation on the critical temperature and the critical current in high-Tc superconducting single crystals YBa 2 Cu 3 O 7-x . The transport current density measured in HTSC single crystals YBa 2 Cu 3 O 7-x by the dc-method was found to exceed 80000 A/cm 2 . The experiments have demonstrated a more than 30-fold increase in the critical current density in single crystals irradiated with 2.5 MeV electrons to a dose of 3·10 18 el/cm 2 . Detailed studies were made into the anisotropy of critical current and the dependence of critical current on the external magnetic field strength in irradiated single crystals. A high efficiency of point defects as centers of magnetic vortex pinning in HTSC single crystals was first demonstrated.

Non-Critical Covariant Superstrings

CERN Document Server

Grassi, P A

2005-01-01

We construct a covariant description of non-critical superstrings in even dimensions. We construct explicitly supersymmetric hybrid type variables in a linear dilaton background, and study an underlying N=2 twisted superconformal algebra structure. We find similarities between non-critical superstrings in 2n+2 dimensions and critical superstrings compactified on CY_(4-n) manifolds. We study the spectrum of the non-critical strings, and in particular the Ramond-Ramond massless fields. We use the supersymmetric variables to construct the non-critical superstrings sigma-model action in curved target space backgrounds with coupling to the Ramond-Ramond fields. We consider as an example non-critical type IIA strings on AdS_2 background with Ramond-Ramond 2-form flux.

Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

International Nuclear Information System (INIS)

Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

2016-01-01

Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study. Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2 /H 2 O binary mixtures are computationally studied here for the first time and their critical parameters are reported.

Critical indices for the Yukawa2 quantum field theory

International Nuclear Information System (INIS)

Bonetto, F.

1997-01-01

The understanding of the Yukawa 2 quantum field theory is still incomplete if the fermionic mass is much smaller than the coupling. We analyze the Schwinger functions for small coupling uniformly in the mass and we find that the asymptotic behavior of the two-point Schwinger function is anomalous and described by two critical indices, related to the renormalization of the mass and of the wave function. The indices are explicitly computed by convergent series in the coupling. (orig.)

Review of studies on criticality safety evaluation and criticality experiment methods

International Nuclear Information System (INIS)

Naito, Yoshitaka; Yamamoto, Toshihiro; Misawa, Tsuyoshi; Yamane, Yuichi

2013-01-01

Since the early 1960s, many studies on criticality safety evaluation have been conducted in Japan. Computer code systems were developed initially by employing finite difference methods, and more recently by using Monte Carlo methods. Criticality experiments have also been carried out in many laboratories in Japan as well as overseas. By effectively using these study results, the Japanese Criticality Safety Handbook was published in 1988, almost the intermediate point of the last 50 years. An increased interest has been shown in criticality safety studies, and a Working Party on Nuclear Criticality Safety (WPNCS) was set up by the Nuclear Science Committee of Organisation Economic Co-operation and Development in 1997. WPNCS has several task forces in charge of each of the International Criticality Safety Benchmark Evaluation Program (ICSBEP), Subcritical Measurement, Experimental Needs, Burn-up Credit Studies and Minimum Critical Values. Criticality safety studies in Japan have been carried out in cooperation with WPNCS. This paper describes criticality safety study activities in Japan along with the contents of the Japanese Criticality Safety Handbook and the tasks of WPNCS. (author)

Critical point in the QCD phase diagram for extremely strong background magnetic fields

International Nuclear Information System (INIS)

Endrödi, Gergely

2015-01-01

Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB<1 GeV 2 . On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB=3.25 GeV 2 . Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.

Upper critical fields in multifilamentary NbTi alloy superconducting wires

International Nuclear Information System (INIS)

Watanabe, Kazuo; Muto, Yoshio; Noto, Koshichi.

1991-01-01

In order to improve the high field performance of superconducting magnets, the upper critical field B c2 for practical multifilamentary alloy wires of NbTi, NbTiTa and NbTiHf were examined in respect with the usage of a pressurized superfluid cooling technique. The addition of Ta or Hf to NbTi enhanced by 0.5 T for B c2 at 1.8 K. Although the addition of a heavy element such as Ta or Hf has been regarded as suppressing Pauli-paramagnetism so far, it was found that the mechanism for B c2 enhancement by Hf addition is different from that by Ta addition. (author)

The low-temperature, high-magnetic-field critical current characteristics of Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V; Yao, Y; Chen, Y; Shi, T; Liu, Y; Khatri, ND; Liu, J; Lei, C; Galstyan, E; Majkic, G

2012-10-26

Critical current performances of state-of-the-art Zr-added (Gd, Y)BaCuO tapes have been investigated over a temperature range of 20-77 K, in magnetic fields up to 9 T and over a wide angular range of magnetic field orientations. The peak in critical current that is commonly observed in the field orientation perpendicular to the tape in BaZrO3 (BZO) containing superconducting tapes is found to vanish at 30 K in magnetic fields at 1-9 T. While the critical current of 15% Zr-added tapes was about 40% lower than that of 7.5% Zr-added tapes at 77 K, the pinning force values of the former were found to be 18-23% higher than those of the latter in the temperature range of 20-40 K and in magnetic fields of 3-5 T. The results from this study emphasize the importance of optimization of coated conductor fabrication processes for optimum performance not just in low magnetic fields at 77 K but also at the operating conditions of low temperatures and high magnetic fields that are of interest, especially for rotating superconducting machinery applications.

The low-temperature, high-magnetic-field critical current characteristics of Zr-added (Gd,Y)Ba2Cu3Ox superconducting tapes

International Nuclear Information System (INIS)

Selvamanickam, V; Yao, Y; Shi, T; Liu, Y; Khatri, N D; Liu, J; Galstyan, E; Majkic, G; Chen, Y; Lei, C

2012-01-01

Critical current performances of state-of-the-art Zr-added (Gd, Y)BaCuO tapes have been investigated over a temperature range of 20–77 K, in magnetic fields up to 9 T and over a wide angular range of magnetic field orientations. The peak in critical current that is commonly observed in the field orientation perpendicular to the tape in BaZrO 3 (BZO) containing superconducting tapes is found to vanish at 30 K in magnetic fields at 1–9 T. While the critical current of 15% Zr-added tapes was about 40% lower than that of 7.5% Zr-added tapes at 77 K, the pinning force values of the former were found to be 18–23% higher than those of the latter in the temperature range of 20–40 K and in magnetic fields of 3–5 T. The results from this study emphasize the importance of optimization of coated conductor fabrication processes for optimum performance not just in low magnetic fields at 77 K but also at the operating conditions of low temperatures and high magnetic fields that are of interest, especially for rotating superconducting machinery applications. (paper)

Effective field study of ising model on a double perovskite structure

Energy Technology Data Exchange (ETDEWEB)

Ngantso, G. Dimitri; El Amraoui, Y. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Benyoussef, A. [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Center of Materials and Nanomaterials, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); El Kenz, A., E-mail: elkenz@fsr.ac.ma [LMPHE, (URAC 12), Faculté des Sciences, Université Mohammed V, Rabat (Morocco)

2017-02-01

By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

Effective field study of ising model on a double perovskite structure

International Nuclear Information System (INIS)

Ngantso, G. Dimitri; El Amraoui, Y.; Benyoussef, A.; El Kenz, A.

2017-01-01

By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one. - Highlights: • Magnetic properties of double perovskite Structure have been studied. • Compensation temperature has been observed below the critical temperature. • Hysteresis behaviors have been studied.

Upper critical fields and critical current densities of Fe-based superconductors as compared to those of other technical superconductors

Energy Technology Data Exchange (ETDEWEB)

Pallecchi, I., E-mail: ilaria.pallecchi@spin.cnr.it [CNR-SPIN, Corso Perrone 24, 16152 Genova (Italy); Tropeano, M. [Columbus Superconductors S.p.A, Via delle Terre Rosse 30, 16133 Genova (Italy); Lamura, G. [CNR-SPIN, Corso Perrone 24, 16152 Genova (Italy); Pani, M. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Palombo, M. [Columbus Superconductors S.p.A, Via delle Terre Rosse 30, 16133 Genova (Italy); Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Dipartimento di Fisica, Universita di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Palenzona, A. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Putti, M. [CNR-SPIN, Corso Perrone 24, 16152 Genova (Italy); Dipartimento di Fisica, Universita di Genova, Via Dodecaneso 33, 16146 Genova (Italy)

2012-11-20

Three years since the discovery by the Hosono's group of Fe-based superconductors, an enormous number of compounds, belonging to several different families have been discovered and fundamental properties have been deeply investigated in order to clarify the interplay between magnetisms and superconductivity in these compounds. Indeed, the actual potential of these compounds for practical applications remains still unclear. Fe-based superconductors are midway between high temperature superconductors (HTSCs) and MgB{sub 2}. In Fe-based superconductors the critical current is rather independent of the field, similarly to HTSCs, as a consequence of the exceptionally high upper critical field and strong pinning associated with nm-scale local modulations of the order parameter. They exhibit low anisotropy of the critical current with respect to the crystalline directions, as in the case of MgB{sub 2}, which allows current flow along the c-axis. However, Fe-based superconductor polycrystalline materials currently available still exhibit electromagnetic granularity, like the HTSCs, which suppresses superconducting current flow over long length. Whether the nature of such granularity is extrinsic, as due to spurious phases or cracks between grains or intrinsic, as related to misalignment of adjacent grains, is under debate. These aspects will be reviewed in the light of the recent literature.

Effective and fundamental quantum fields at criticality

Energy Technology Data Exchange (ETDEWEB)

Scherer, Michael

2010-10-28

We employ Wetterich's approach to functional renormalization as a suitable method to investigate universal phenomena in non-perturbative quantum field theories both qualitatively and quantitatively. Therefore we derive and investigate flow equations for a class of chiral Yukawa models with and without gauge bosons and reveal fixed-point mechanisms. In four dimensions chiral Yukawa systems serve as toy models for the standard model Higgs sector and show signatures of asymptotically safe fixed points by a balancing of bosonic and fermionic contributions. In the approximations investigated this renders the theory fundamental and solves the triviality problem. Further, we obtain predictions for the Higgs mass and even for the top mass of our toy model. In three dimensions we compute the critical exponents which define new universality classes and provide benchmark values for systems of strongly correlated chiral fermions. In a Yukawa system of non-relativistic two-component fermions a fixed point dominates the renormalization flow giving rise to universality in the BCS-BEC crossover. We push the functional renormalization method to a quantitative level and we compute the critical temperature and the single-particle gap with a considerable precision for the whole crossover. Finally, we provide further evidence for the asymptotic safety scenario in quantum gravity by confirming the existence of an ultraviolet fixed point under inclusion of a curvature-ghost coupling. (orig.)

Effective and fundamental quantum fields at criticality

International Nuclear Information System (INIS)

Scherer, Michael

2010-01-01

We employ Wetterich's approach to functional renormalization as a suitable method to investigate universal phenomena in non-perturbative quantum field theories both qualitatively and quantitatively. Therefore we derive and investigate flow equations for a class of chiral Yukawa models with and without gauge bosons and reveal fixed-point mechanisms. In four dimensions chiral Yukawa systems serve as toy models for the standard model Higgs sector and show signatures of asymptotically safe fixed points by a balancing of bosonic and fermionic contributions. In the approximations investigated this renders the theory fundamental and solves the triviality problem. Further, we obtain predictions for the Higgs mass and even for the top mass of our toy model. In three dimensions we compute the critical exponents which define new universality classes and provide benchmark values for systems of strongly correlated chiral fermions. In a Yukawa system of non-relativistic two-component fermions a fixed point dominates the renormalization flow giving rise to universality in the BCS-BEC crossover. We push the functional renormalization method to a quantitative level and we compute the critical temperature and the single-particle gap with a considerable precision for the whole crossover. Finally, we provide further evidence for the asymptotic safety scenario in quantum gravity by confirming the existence of an ultraviolet fixed point under inclusion of a curvature-ghost coupling. (orig.)

The first critical field, Hc1perpendicularto, and the penetration depth in dirty superconducting S/N multilayers

International Nuclear Information System (INIS)

Golubov, A.A.; Krasnov, V.M.

1992-01-01

The proximity effect in dirty S/N multilayers is studied theoretically. The structure of the Abrikosov vortex and the first critical field, H c1 perpendicular to , in a perpendicular magnetic field is investigated. Our approach is based on solving Ginzburg-Landau and Usadel equations with boundary conditions applicable to real structures. It was shown that for highly conducting N-layers there exists a positive curvature on H c1 (T) dependences. (orig.)

Chemical Distances for Percolation of Planar Gaussian Free Fields and Critical Random Walk Loop Soups

Science.gov (United States)

Ding, Jian; Li, Li

2018-06-01

We initiate the study on chemical distances of percolation clusters for level sets of two-dimensional discrete Gaussian free fields as well as loop clusters generated by two-dimensional random walk loop soups. One of our results states that the chemical distance between two macroscopic annuli away from the boundary for the random walk loop soup at the critical intensity is of dimension 1 with positive probability. Our proof method is based on an interesting combination of a theorem of Makarov, isomorphism theory, and an entropic repulsion estimate for Gaussian free fields in the presence of a hard wall.

Critical current anisotropy in Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} multifilamentary tapes: influence of self-magnetic field

Energy Technology Data Exchange (ETDEWEB)

Majoros, M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava (Slovakia); Glowacki, B A [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Department of Materials Science and Metallurgy, University of Cambridge, Cambridge (United Kingdom); Campbell, A M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom)

2001-06-01

Two factors affect critical current anisotropy in multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tapes - the intrinsic material anisotropy and the geometry. Experimental results on the magnetic field dependence and anisotropy of the critical current in a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tape after correction for self-magnetic field effects were found to fit the anisotropic Kim relation. Based on this relation a finite-element-method numerical code for solving the nonlinear Poisson equation for vector magnetic potential was adopted. It allowed the experimental data to be reproduced by back calculation and made possible the study of the interplay of self and external magnetic fields in different cases with well defined physical parameters of the material. The model was used to analyse the distribution of the critical current in individual filaments as well as to evaluate the influence of their geometrical arrangements on the critical current of the tape. The self-field critical current of an individual filament 'extracted' from the tape was compared with the critical current of the overall tape. The effect of the self-magnetic field on critical current distribution obtained by the cutting method was determined. The critical currents of the tapes with different cross sections were calculated and compared with experiments and the influence of the self-field was analysed. The anisotropic properties of a low anisotropy architecture of a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} conductor were studied. The dependence of critical currents (normalized to self-field critical currents) on external magnetic field corrected for the self-field was found to follow nearly the same curves as those for tapes with different critical current densities (in the range 20-70 kA cm{sup -2} in a self-field), which makes the numerical model applicable to different tapes. (author)

Critical behavior of the anisotropic Heisenberg model by effective-field renormalization group

Science.gov (United States)

de Sousa, J. Ricardo; Fittipaldi, I. P.

1994-05-01

A real-space effective-field renormalization-group method (ERFG) recently derived for computing critical properties of Ising spins is extended to treat the quantum spin-1/2 anisotropic Heisenberg model. The formalism is based on a generalized but approximate Callen-Suzuki spin relation and utilizes a convenient differential operator expansion technique. The method is illustrated in several lattice structures by employing its simplest approximation version in which clusters with one (N'=1) and two (N=2) spins are used. The results are compared with those obtained from the standard mean-field (MFRG) and Migdal-Kadanoff (MKRG) renormalization-group treatments and it is shown that this technique leads to rather accurate results. It is shown that, in contrast with the MFRG and MKRG predictions, the EFRG, besides correctly distinguishing the geometries of different lattice structures, also provides a vanishing critical temperature for all two-dimensional lattices in the isotropic Heisenberg limit. For the simple cubic lattice, the dependence of the transition temperature Tc with the exchange anisotropy parameter Δ [i.e., Tc(Δ)], and the resulting value for the critical thermal crossover exponent φ [i.e., Tc≂Tc(0)+AΔ1/φ ] are in quite good agreement with results available in the literature in which more sophisticated treatments are used.

$P-V$ criticality of a specific black hole in $f(R)$ gravity coupled with Yang-Mills field arXiv

CERN Document Server

Övgün, Ali

In this paper, we study the $P-v$ criticality of a specific charged AdS type black hole (SBH) in $f(R)$ gravity coupled with Yang-Mills field. In the extended phase space, we treat the cosmological constant as a thermodynamic pressure. After we study the various thermodynamical quantities, we show that the thermodynamic properties of the SBH behave as a Van der Waals liquid-gas system at the critical points and there is a first order phase transition between small-large SBH.

Field measurements of supermarket refrigeration systems. Part I: Analysis of CO2 trans-critical refrigeration systems

International Nuclear Information System (INIS)

Sawalha, Samer; Karampour, Mazyar; Rogstam, Jörgen

2015-01-01

This study investigates the refrigeration performance of three CO 2 trans-critical solutions based on field measurements. The measurements are carried out in five supermarkets in Sweden. Using the field measurements, low and medium temperature level cooling capacities and COP's are calculated for ten-minute intervals, filtered and averaged to monthly values. The results indicate that the systems using trans-critical booster system with gas removal from the intermediate vessel have relatively the highest total COP. The reasons are higher evaporation temperatures, lower internal and external superheat and higher total efficiency of booster compressors. Another important factor is gas removal from the intermediate vessel which leads to higher COP of low temperature level. Comparing the older and newer installed systems, a trend in energy efficiency improvement has been seen. The study shows this improvement originates from both changes in the system design (e.g. two stage expansion) and components efficiency improvement (e.g. higher total efficiency of compressors - lower internal superheat and higher evaporation temperatures of cabinets). - Highlights: • Five Swedish supermarkets using three CO 2 refrigeration solutions are analyzed. • A trend of improvement in energy efficiency has been observed. • Parallel CO 2 system with indirect heat rejection offers the lowest energy efficiency. • CO 2 trans-critical booster with gas removal achieves up to 35% COP improvement

Pulsed critical current measurements of NbTi in perpendicular and parallel pulsed magnetic fields using the new Cryo-BI-Pulse System

International Nuclear Information System (INIS)

Stehr, V; Tan, K S; Hopkins, S C; Glowacki, B A; Keyser, A De; Bockstal, L Van; Deschagt, J

2006-01-01

Rapid transport current versus high magnetic field characterisation of high-irreversibility type II superconductors is important to maximise their critical parameters. HTS conductors are already used to produce insert coils that increase the fields of conventional magnets made from NbTi (Nb, Ta) 3 Sn and Nb 3 Al wires. There is fundamental interest in the study of HTS tapes and wires in magnetic fields higher than 21T, the current limit of superconducting magnets producing a DC field. Such fields can be obtained by using pulse techniques. High critical currents cannot be routinely measured with a continuous current applied at liquid helium, hydrogen or neon temperatures because of thermal and mechanical effects. A newly developed pulsed magnetic field and pulsed current system which allows rapid J c (B, T) measurements of the whole range of superconducting materials was tested with a multifilamentary NbTi wire in perpendicular and parallel orientations

Magnetic field-aligned plasma expansion in critical ionization velocity space experiments

International Nuclear Information System (INIS)

Singh, N.

1989-01-01

Motivated by the recent Critical Ionization Velocity (CIV) experiments in space, the temporal evolution of a plasma cloud released in an ambient plasma is studied. Time-dependent Vlasov equations for both electrons and ions, along with the Poisson equation for the self-consistent electric field parallel to the ambient magnetic field, are solved. The initial cloud is assumed to consist of cold, warm, and hot electrons with temperatures T/sub c/ ≅ 0.2 eV, T/sub w/ ≅ 2 eV, and T/sub h/ ≅ 10 eV, respectively. It is found that the minor hot electrons escape the cloud, and their velocity distribution function shows the typical time-of-flight dispersion feature - that is, the larger the distance from the cloud, the larger is the average drift velocity of the escaping electrons. The major warm electrons expand along the magnetic field line with the corresponding ion-acoustic speed. The combined effect of the escaping hot electrons and the expanding warm ones sets up an electric potential structure which accelerates the ambient electrons into the cloud. Thus, the energy loss due to the electron escape is partly replenished. The electric field distribution in the potential structure depends on the stage of the evolution; before the rarefaction waves propagating from the edges of the cloud reach its center, the electric fields point into the cloud. After this stage the cloud divides into two subclouds, with each having their own bipolar electric fields. Effects of collisions on the evolution of plasma clouds are also discussed. The relevance of the results seen from the calculations are discussed in the context of recent space experiments on CIV

Further investigations of the upper critical field and the high field critical current density in Nb-Ti and its alloys

International Nuclear Information System (INIS)

Hawksworth, D.G.; Larbalestier, D.C.

1980-09-01

This paper reports further measurements of Hc 2 in the Nb-Ti-Ta and Nb-Ti-Hf systems. Whilst we find only small enhancements of approx. 0.3 Tesla in μ 0 Hc 2 (4.2 0 K) compared to binary Nb-Ti, at 2 0 K there is a wide composition range in the Nb-Ti-Ta system where μ 0 Hc 2 (2 0 K) exceeds 15 Tesla, reaching a maximum of 15.5 Tesla. This represents an enhancement of 1.3 Tesla over unalloyed Nb-Ti. By comparison alloys in the Nb-Ti-Hf system show a maximum enhancement in μ 0 Hc 2 (2 0 K) of only 0.3 Tesla. The reasons both for the enhancements in Hc 2 and for the differences in behavior shown by alloys containing Ta and Hf are briefly discussed. This paper also discusses common features in the behavior of the high field critical current density, J/sub c/, of four commercial Nb-Ti composites and upon the basis of this behavior predict the enhancements in high field J/sub c/ to be expected from using Nb-Ti-Ta and its alloys

Field-induced magnetic instability and quantum criticality in the antiferromagnet CeCu2Ge2.

Science.gov (United States)

Liu, Yi; Xie, Donghua; Wang, Xiaoying; Zhu, Kangwei; Yang, Ruilong

2016-01-13

The magnetic quantum criticality in strongly correlated electron systems has been considered to be closely related with the occurrence of unconventional superconductivity. Control parameters such as magnetic field, pressure or chemical doping are frequently used to externally tune the quantum phase transition for a deeper understanding. Here we report the research of a field-induced quantum phase transition using conventional bulk physical property measurements in the archetypal antiferromagnet CeCu2Ge2, which becomes superconductive under a pressure of about 10 GPa with Tc ~ 0.64 K. We offer strong evidence that short-range dynamic correlations start appearing above a magnetic field of about 5 T. Our demonstrations of the magnetic instability and the field-induced quantum phase transition are crucial for the quantum criticality, which may open a new route in experimental investigations of the quantum phase transition in heavy-fermion systems.

Nonlinear field theories and non-Gaussian fluctuations for near-critical many-body systems

International Nuclear Information System (INIS)

Tuszynski, J.A.; Dixon, J.M.; Grundland, A.M.

1994-01-01

This review article outlines a number of efforts made over the past several decades to understand the physics of near critical many-body systems. Beginning with the phenomenological theories of Landau and Ginzburg the paper discusses the two main routes adopted in the past. The first approach is based on statistical calculations while the second investigates the underlying nonlinear field equations. In the last part of the paper we outline a generalisation of these methods which combines classical and quantum properties of the many-body systems studied. (orig.)

Enhancement of the critical current density in FeO-coated MgB2 thin films at high magnetic fields

Directory of Open Access Journals (Sweden)

Andrei E. Surdu

2011-12-01

Full Text Available The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB2 thin films on the critical current density was studied in comparison with the case of uncoated MgB2 thin films. We calculated the superconducting critical current densities (Jc from the magnetization hysteresis (M–H curves for both sets of samples and found that the Jc value of FeO-coated films is higher at all fields and temperatures than the Jc value for uncoated films, and that it decreases to ~105 A/cm2 at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.

Critical phenomena in Ising-type thin films by Monte Carlo study

International Nuclear Information System (INIS)

Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.

2016-01-01

The magnetic properties of ferrimagnetic spin-2 and 3/2 Ising-typed thin films are studied by Monte Carlo simulation. The critical temperature is obtained for different values of thickness of the thin film and for different exchange interactions. The total magnetization has been determined for different values of exchange interactions in surface and in bulk and different temperatures. The magnetic hysteresis cycle is obtained for different values of exchange interactions ferro and antiferromagnetic in the surface and in the bulk and for different values of temperatures for a fixed size of the film thickness. The coercive field increase with increasing the film thickness. - Highlights: • The magnetic properties of thin films are studied by Monte Carlo simulation. • The critical temperature is obtained for different values of thickness of thin film. • The magnetic hysteresis cycle is obtained in the surface and in the bulk. • The coercive field increase with increasing the thin film thickness.

Critical phenomena in Ising-type thin films by Monte Carlo study

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63, 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

2016-04-01

The magnetic properties of ferrimagnetic spin-2 and 3/2 Ising-typed thin films are studied by Monte Carlo simulation. The critical temperature is obtained for different values of thickness of the thin film and for different exchange interactions. The total magnetization has been determined for different values of exchange interactions in surface and in bulk and different temperatures. The magnetic hysteresis cycle is obtained for different values of exchange interactions ferro and antiferromagnetic in the surface and in the bulk and for different values of temperatures for a fixed size of the film thickness. The coercive field increase with increasing the film thickness. - Highlights: • The magnetic properties of thin films are studied by Monte Carlo simulation. • The critical temperature is obtained for different values of thickness of thin film. • The magnetic hysteresis cycle is obtained in the surface and in the bulk. • The coercive field increase with increasing the thin film thickness.

Magnetization, critical current, and injection field harmonics in superconducting accelerator magnets

International Nuclear Information System (INIS)

Ghosh, A.K.; Sampson, W.B.; Wanderer, P.

1985-01-01

The very large energy ratio of machines such as the SSC dictates rather low injection field (for 6T, 20 TeV it is approximately 0.3T). Since the harmonic content at such low fields is largely determined by magnetization currents in the superconductor, the random errors depend on the uniformity of the superconducting wire. In principle the magnitude of the residual fields can be reduced indefinitely by using finer filaments, but in practice there is a lower limit of a few microns. We have compared the injection field harmonics for a number of accelerator dipoles with magnetization measurements made on samples of the conductor used to wind the coils. In addition both the magnetization and harmonics have been compared with short sample critical current measurements made at 5T. The results indicated that an accurate estimate of the variation in injection field harmonics can only be obtained from direct measurements of the magnetization of the cable. It appears feasible to use such measurements to ''shuffle'' magnets for a large accelerator by predicting the low field properties of a magnet before actually winding the coils. 10 refs., 4 figs., 2 tabs

Conformal scalar field on the hyperelliptic curve and critical Ashkin-Teller multipoint correlation functions

International Nuclear Information System (INIS)

Zamolodchikov, A.B.

1987-01-01

A multipoint conformal block of Ramond states of the two-dimensional free scalar field is calculated. This function is related to the free energy of the scalar field on the hyperelliptic Riemann surface under a particular choice of boundary conditions. Being compactified on the circle this field leads to the crossing symmetric correlation functions with a discrete spectrum of scale dimensions. These functions are supposed to describe multipoint spin correlations of the critical Ashkin-Teller model. (orig.)

SANS studies of critical phenomena in ternary mixtures

CERN Document Server

Bulavyn, L A; Hohryakov, A; Garamus, V; Avdeev, M; Almasy, L

2002-01-01

Critical behaviour of a quasi-binary liquid mixture is investigated by small-angle neutron scattering. Analysis of the changes of the critical parameters, caused by addition of a small amount of electrolyte into the binary mixture 3-methylpyridine-heavy water, shows that the third component does not change the 3D Ising-type behaviour of the system; a crossover towards the mean-field behaviour is not observed. (orig.)

Critical Thinking: Discovery of a Misconception

Science.gov (United States)

Rohrer, Sandie

2014-01-01

Critical thinking skills in the healthcare field are imperative when making quick-thinking decisions. This descriptive comparative study investigated to what extent completing a critical thinking course improved college students' critical thinking skills. The study further investigated whether the instructors' critical thinking skills were…

Tuning critical failure with viscoelasticity: How aftershocks inhibit criticality in an analytical mean field model of fracture.

Science.gov (United States)

Baro Urbea, J.; Davidsen, J.

2017-12-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible of deformation. Avalanche models involving critical failure have determined universality classes in different systems: from slip events in crystalline and amorphous materials to the jamming of granular media or the fracture of brittle materials. However, not all empirical failure processes exhibit the trademarks of critical failure. As an example, the statistical properties of ultrasonic acoustic events recorded during the failure of porous brittle materials are stationary, except for variations in the activity rate that can be interpreted in terms of aftershock and foreshock activity (J. Baró et al., PRL 2013).The rheological properties of materials introduce dissipation, usually reproduced in atomistic models as a hardening of the coarse-grained elements of the system. If the hardening is associated to a relaxation process the same mechanism is able to generate temporal correlations. We report the analytic solution of a mean field fracture model exemplifying how criticality and temporal correlations are tuned by transient hardening. We provide a physical meaning to the conceptual model by deriving the constitutive equation from the explicit representation of the transient hardening in terms of a generalized viscoelasticity model. The rate of 'aftershocks' is controlled by the temporal evolution of the viscoelastic creep. At the quasistatic limit, the moment release is invariant to rheology. Therefore, the lack of criticality is explained by the increase of the activity rate close to failure, i.e. 'foreshocks'. Finally, the avalanche propagation can be reinterpreted as a pure mathematical problem in terms of a stochastic counting process. The statistical properties depend only on the distance to a critical point, which is universal for any

DTADH and quantum critical phenomena caused by anisotropy and external magnetic field for spin-1/2 Heisenberg diamond chains

International Nuclear Information System (INIS)

Li Yanchao

2010-01-01

Using the transfer matrix renormalization group (TMRG) method, we study the connection between the first derivative of the thermal average of driving-term Hamiltonian (DTADH) and the trace of quantum critical behaviors at finite temperatures. Connecting with the exact diagonalization method, we give the phase diagrams and analyze the properties of each phase for both the ferromagnetic and anti-ferromagnetic frustrated J 3 anisotropy diamond chain models. The finite-temperature scaling behaviors near the critical regions are also investigated. Further, we show the critical behaviors driven by external magnetic field, analyze the formation of the 1/3 magnetic plateau and the influence of different interactions on those critical points for both the ferrimagnetic and anti-ferromagnetic distorted diamond chains.

Quantum critical scaling for field-induced quantum phase transition in a periodic Anderson-like model polymer chain

Energy Technology Data Exchange (ETDEWEB)

Ding, L.J., E-mail: dinglinjie82@126.com; Zhong, Y.

2017-07-15

Highlights: • The quantum critical scaling is investigated by Green’s function theory. • The obtained power-law critical exponents (β, δ and α) obey the critical scaling relation α + β(1 + δ) = 2. • The scaling hypothesis equations are proposed to verify the scaling analysis. - Abstract: The quantum phase transition and thermodynamics of a periodic Anderson-like polymer chain in a magnetic field are investigated by Green’s function theory. The T-h phase diagram is explored, wherein a crossover temperature T{sup ∗} denoting the gapless phase crossover into quantum critical regimes, smoothly connects near the critical fields to the universal linear line T{sup ∗} ∼ (h − h{sub c,s}), and ends at h{sub c,s}, providing a new route to capture quantum critical point (QCP). The quantum critical scaling around QCPs is demonstrated by analyzing magnetization, specific heat and Grüneisen parameter Γ{sub h}, which provide direct access to distill the power-law critical exponents (β, δ and α) obeying the critical scaling relation α + β(1 + δ) = 2, analogous to the quantum spin system. Furthermore, scaling hypothesis equations are proposed to check the scaling analysis, for which all the data collapse onto a single curve or two independent branches for the plot against an appropriate scaling variable, indicating the self-consistency and reliability of the obtained critical exponents.

Angular dependence of the upper critical field in Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta

CERN Document Server

Vedeneev, S I

2002-01-01

The angular dependence of the upper critical field has been investigated in a wide range of temperatures in very high-quality Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta single crystals with critical temperature approx = 9 K in magnetic fields up to 28 T. Although the typical value of the normal state resistivity ratio approx = 10 sup 4 , the anisotropy ratio of the upper critical fields is much smaller. A model is proposed based on a strong anisotropy and a small transparency between superconducting layers

Two-dimensional critical phenomena

International Nuclear Information System (INIS)

Saleur, H.

1987-09-01

Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields

Science.gov (United States)

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

Science.gov (United States)

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (H c2 ) and critical temperature (T c ). The critical current (I c ) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new I c measurement system that can carry out accurate I c measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The I c measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa 2 Cu 3 O 7-x (YBCO) tapes I c determination with different temperatures and magnetic fields.

Temperature dependence of the upper critical field of type II superconductors with fluctuation effects

International Nuclear Information System (INIS)

Mikitik, G.P.

1992-01-01

Fluctuations of the order parameter are taken into consideration in an analysis of the temperature dependence of the upper critical field of a type II superconductor with a three-dimensional superconductivity. This temperature dependence is of universal applicability, to all type II superconductors, if the magnetic fields and temperatures are expressed in appropriate units. This dependence is derived explicitly for the regions of strong and weak magnetic fields. The results are applied to high T c superconductors, for which fluctuation effects are important. For these superconductors, the H c2 (T) dependence is quite different from the linear dependence characteristic of the mean-field theory, over a broad range of magnetic fields

Field, temperature, and angle dependent critical current density Jc(H,T, ) in coated conductors obtained via contact-free methods

Energy Technology Data Exchange (ETDEWEB)

Thompson, James R [ORNL; Sinclair IV, John W [ORNL; Christen, David K [ORNL; Zhang, Yifei [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

2010-01-01

Applications of coated conductors based on high-Tc superconductors often require detailed knowledge of their critical current density Jc as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods to obtain the angularly dependent Jc using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

Perceptions of Field Instructors: What Skills are Critically Important inManaged Care and Privatized Environments?

Directory of Open Access Journals (Sweden)

Michael N. Kane

2000-12-01

Full Text Available There is an increasing demand for social work practitioners to work in managed care and privatized environments. In an attempt to build social work curriculum and identify important competencies needed in contemporary service environments, researchers investigated South Florida field instructors’ (N=79 perceptions of necessary knowledge and skill to work in environments affected by privatization and managed care. This study’s findings indicate that field instructors (98% identified documentation as the most critically important skill for any social work position. Additionally, respondents identified intervention evaluation (95%, time focused and needs-based assessments strategies (94%, and evaluation of progress through outcome measures (94% as other critically important skills for current and future practitioners.

Methodological aspects of functional neuroimaging at high field strength: a critical review

International Nuclear Information System (INIS)

Scheef, L.; Landsberg, M.W.; Boecker, H.

2007-01-01

The last few years have proven that high field magnetic resonance imaging (MRI) is superior in nearly every way to conventional equipment up to 1.5 tesla (T). Following the global success of 3T-scanners in research institutes and medical practices, a new generation of MRI devices with field strengths of 7T and higher is now on the horizon. The introduction of ultra high fields has brought MRI technology closer to the physical limitations and increasingly greater costs are required to achieve this goal. This article provides a critical overview of the advantages and problems of functional neuroimaging using ultra high field strengths. This review is principally limited to T2*-based functional imaging techniques not dependent on contrast agents. The main issues include the significance of high field technology with respect to SNR, CNR, resolution, and sequences, as well as artifacts, noise exposure, and SAR. Of great relevance is the discussion of parallel imaging, which will presumably determine the further development of high and ultra high field strengths. Finally, the importance of high field strengths for functional neuroimaging is explained by selected publications. (orig.)

Critical currents in columnar vanadium films

International Nuclear Information System (INIS)

Cherkasova, V.G.; Kolin'ko, A.E.; Slatin, A.E.; Fogel, N.Y.

1982-01-01

The angular dependence of the critical current I/sub c/ is studied in columnar vanadium films. In measurements in constant magnetic fields an anomalous maximum I/sub c/ is found on the I/sub c/(theta) curves at arbitrary values of the external magnetic field and temperature, when the magnetic field is perpendicular to the plane of the specimen. The angular dependence of I/sub c/ measured in constant reduced magnetic fields h = H/H/sub c/2(T,theta) shows no singularities in the vicinity of the angle at which the I/sub c/ peak is found in the case H = const, i.e., the critical current is isotropic. This implies that a change in the relative orientation of the vortices and column boundaries produces no change in critical current. The experimental data obtained permit the conclusion that the anisotropy of I/sub c/ observed in a constant magnetic field H is merely a consequence of the anisotropy of the critical magnetic field H/sub c/: the critical current ''tracking'' the magnitude and angular dependence of H/sub c/

Measurements of the surface impedance and the ac critical field of superconducting thin tin films at 10 GHz

International Nuclear Information System (INIS)

Spencer, G.L.

1976-01-01

The surface impedances and ac critical fields of superconducting thin tin films were studied. These experiments were performed using a superconducting frequency stabilized microwave cavity of high Q. Measurements of the power losses in the cavity and the center frequency of the cavity were used to determine the surface impedance and the critical field of a thin film sample placed in the cavity. In this case a theoretical treatment based on a model proposed by I.O. Kulik was used to fit the data. The general agreement between the modified Kulik treatment and the data, obtained in this experiment, was substantial. The second method was to modify the thin film data to correspond to a bulk situation. This modification was accomplished by taking into account the measuring techniques used and the geometric consideration inherent in the experiment. The comparison between the modified experimental data and calculations obtained from the Mattis-Bardeen bulk model was generally very good. One aspect of the results which was not explained was the presence of a slight increase in the surface resistance in the vicinity of the transition temperature. The critical field measurements were compared to the (1 - (T/T/sub c/)/sup 1/2) dependence predicted by Bardeen. If it is assumed that substantial microwave heating took place in the sample near T/sub c/, then remarkable agreement with the Bardeen model can be reached

Critical Analysis of Multimodal Discourse

DEFF Research Database (Denmark)

van Leeuwen, Theo

2013-01-01

This is an encyclopaedia article which defines the fields of critical discourse analysis and multimodality studies, argues that within critical discourse analysis more attention should be paid to multimodality, and within multimodality to critical analysis, and ends reviewing a few examples of re...

Thermodynamic parameters of single- or multi-band superconductors derived from self-field critical currents

Energy Technology Data Exchange (ETDEWEB)

Talantsev, Evgueni [Robinson Research Institute, Victoria University of Wellington, Lower Hutt (New Zealand); Crump, Wayne P.; Tallon, Jeffery L. [Robinson Research Institute, Victoria University of Wellington, Lower Hutt (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt (New Zealand)

2017-12-15

Key questions for any superconductor include: what is its maximum dissipation-free electrical current (its 'critical current') and can this be used to extract fundamental thermodynamic parameters? Present models focus on depinning of magnetic vortices and implicate materials engineering to maximise pinning performance. But recently we showed that the self-field critical current for thin films is a universal property, independent of microstructure, controlled only by the penetration depth. Here, using an extended BCS-like model, we calculate the penetration depth from the temperature dependence of the superconducting energy gap thus allowing us to fit self-field critical current data. In this way we extract from the T-dependent gap a set of key thermodynamic parameters, the ground-state penetration depth, energy gap and jump in electronic specific heat. Our fits to 79 available data sets, from zinc nanowires to compressed sulphur hydride with critical temperatures of 0.65 to 203 K, respectively, are excellent and the extracted parameters agree well with reported bulk values. Samples include thin films, wires or nanowires of single- or multi-band s-wave and d-wave superconductors of either type I or type II. For multiband or multiphase samples we accurately recover individual band contributions and phase fractions. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Sport Management Student as Producer: Embedding Critical Management Studies in Sport through Contemporary Pedagogy

OpenAIRE

Zervas, K; Glazzard, J

2017-01-01

In recent years there has been growing interest over the role of major sport events and the sports industry. The aftermath of 2008 global crisis exposed the myth of ‘end of history’ and raised several questions over the role of management and organisational practices and theories in all aspects of human activity, including sport. This article reviews the emergence of critical management studies (CMS) as a field within management and organisational studies. We focus on critical performativity ...

Critical behavior of mean-field spin glasses on a dilute random graph

Energy Technology Data Exchange (ETDEWEB)

De Sanctis, Luca [Dipartimento di Matematica e di Psicologia, Universita di Bologna, P.zza di Porta San Donato 5, 40126 Bologna (Italy); Barra, Adriano; Folli, Viola [Dipartimento di Fisica, Universita La Sapienza, P.le Aldo Moro 5, 00185 Roma (Italy)], E-mail: desanctis@dm.unibo.it, E-mail: adriano.barra@roma1.infn.it, E-mail: viola.folli@roma1.infn.it

2008-05-30

We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.

Critical behavior of mean-field spin glasses on a dilute random graph

International Nuclear Information System (INIS)

De Sanctis, Luca; Barra, Adriano; Folli, Viola

2008-01-01

We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof

On the magnon interaction in Haematite. 2: Magnon energy of the acoustical mode and magnetic critical fields

Science.gov (United States)

Bonavito, N. L.; Nagai, O.; Tanaka, T.

1975-01-01

Previous spin wave theories of the antiferromagnet hematite were extended. The behavior of thermodynamic quantities around the Morin transition temperature was studied, and the latent heat of the Morin transition was calculated. The temperature dependence of the antiferromagnetic resonance frequency and the parallel and perpendicular critical spin-flop magnetic fields were calculated. It was found that the theory agrees well with experiment.

Universal Signatures of Quantum Critical Points from Finite-Size Torus Spectra: A Window into the Operator Content of Higher-Dimensional Conformal Field Theories.

Science.gov (United States)

Schuler, Michael; Whitsitt, Seth; Henry, Louis-Paul; Sachdev, Subir; Läuchli, Andreas M

2016-11-18

The low-energy spectra of many body systems on a torus, of finite size L, are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2+1)D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1/L. We highlight the implications of a neighboring topological phase on the spectrum by studying the Ising* transition (i.e. the transition between a Z_{2} topological phase and a trivial paramagnet), in the example of the toric code in a longitudinal field, and advocate a phenomenological picture that provides qualitative insight into the operator content of the critical field theory.

Critical properties of the classical XY and classical Heisenberg models: A renormalization group study

Science.gov (United States)

de Sousa, J. Ricardo; de Albuquerque, Douglas F.

1997-02-01

By using two approaches of renormalization group (RG), mean field RG (MFRG) and effective field RG (EFRG), we study the critical properties of the simple cubic lattice classical XY and classical Heisenberg models. The methods are illustrated by employing its simplest approximation version in which small clusters with one ( N‧ = 1) and two ( N = 2) spins are used. The thermal and magnetic critical exponents, Yt and Yh, and the critical parameter Kc are numerically obtained and are compared with more accurate methods (Monte Carlo, series expansion and ε-expansion). The results presented in this work are in excellent agreement with these sophisticated methods. We have also shown that the exponent Yh does not depend on the symmetry n of the Hamiltonian, hence the criteria of universality for this exponent is only a function of the dimension d.

My Critique is Bigger than Yours: Constituting Exclusions in Critical Security Studies

Directory of Open Access Journals (Sweden)

David Roger Mutimer

2009-10-01

Full Text Available Critical Security Studies proceeds from the premise that words are world-making, that is that the ways we think about security are constitutive of the worlds of security we analyse. Turned to conventional security studies and the practices of global politics, this critical insight has revealed the ways in which the exclusions that are the focus of this conference have been produced. Perhaps most notable in this regard has been David Campbell's work, showing how the theory and practice of security are an identity discourse producing both insides and outsides, but the production of excluded others is a theme that runs through the critical scholarship on security in the past decade or more. This article turns the critical security studies gaze on itself, to explore the field's own complicity in the production of exclusions. The article reads three important instances of critical security studies for the inclusions and exclusions they produce: Ken Booth's Theory of World Securitv, the epilogue to David Campbell's Writing Security, and the CASE Collective Manifesto. The article concludes by asking about the nature of the inclusions and exclusions these divisions produce and the politics which those exclusions, in turn, (reproduce.

Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

Energy Technology Data Exchange (ETDEWEB)

Helm, T. [MPI-CPFS (Germany); Bachmann, M. [MPI-CPFS (Germany); Moll, P.J.W. [MPI-CPFS (Germany); Balicas, L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Chan, Mun Keat [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramshaw, Brad [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Balakirev, Fedor Fedorovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bauer, Eric Dietzgen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ronning, Filip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-03-23

Electronic nematicity appears in proximity to unconventional high-temperature superconductivity in the cuprates and iron-arsenides, yet whether they cooperate or compete is widely discussed. While many parallels are drawn between high-T_c and heavy fermion superconductors, electronic nematicity was not believed to be an important aspect in their superconductivity. We have found evidence for a field-induced strong electronic in-plane symmetry breaking in the tetragonal heavy fermion superconductor CeRhIn₅. At ambient pressure and zero field, it hosts an anti-ferromagnetic order (AFM) of nominally localized 4f electrons at TN=3.8K(1). Moderate pressure of 17kBar suppresses the AFM order and a dome of superconductivity appears around the quantum critical point. Similarly, a density-wave-like correlated phase appears centered around the field-induced AFM quantum critical point. In this phase, we have now observed electronic nematic behavior.

Exploring critical thinking in critical care nursing education: a pilot study.

Science.gov (United States)

Rogal, Sonya M; Young, Jeanne

2008-01-01

Critical care nurses process vast amounts of information and require well developed critical-thinking skills to make clinical decisions. Using a pretest posttest design, the critical-thinking skills of 31 postgraduate nurses were evaluated using the California Critical Thinking Skills Test (CCTST). For the total group, mean critical-thinking scores improved slightly over time. The CCTST revealed a mean pretest score of 18.5 and a mean posttest score of 19.7, both of which were higher than the established norms for the test. Overall, no significant difference was observed between pretest and posttest. However, statistical significance was observed posttest for nurses whose critical-thinking scores improved (p critical-thinking skills during the course of their study.

Beyond Capitalist Realism - Why We Need Critical Future Studies

Directory of Open Access Journals (Sweden)

Luke Goode

2017-06-01

Full Text Available This paper introduces the interdisciplinary field of Critical Future Studies (CFS. CFS investigates the scope and constraints within public culture for imagining and debating different potential futures. It interrogates imagined futures founded - often surreptitiously - upon values and assumptions from the past and present, as well as those representing a departure from current social trajectories. CFS draws on perspectives from various disciplines including sociology, political studies, intellectual history, cultural history, media and cultural studies, utopian studies, science and technology studies, and philosophy. CFS also engages with discourses and ideas from the natural sciences (including popular science, computing and economics. And, given our concern with public culture, CFS aims to contribute constructively to vigorous and imaginative public debate about the future - a futural public sphere - and to challenge a prevalent contemporary cynicism about our capacity to imagine alternative futures while trapped in a parlous present. To that extent, we propose CFS as a programme of engaged and open-ended social critique, not as a solely academic endeavour. Our paper begins by describing the relationship between CFS and mainstream Future Studies. Subsequently, we discuss the contemporary context for Critical Future Studies. Here we make the case that CFS is a timely and even urgent project at our current historical juncture, arguing also for the significance of both utopian and dystopian imaginings. We then go on to discuss methodologies within CFS scholarship. Finally, we conclude by reflecting on the values underpinning CFS. Overall, this paper not only describes CFS as a field of research but also serves as an invitation to cultural scholars to consider how their own work might intersect with and contribute to CFS.

Digital subjectivation and financial markets: Criticizing Social Studies of Finance with Lazzarato

Directory of Open Access Journals (Sweden)

Tim Christiaens

2016-08-01

Full Text Available The recently rising field of Critical Data Studies is still facing fundamental questions. Among these is the enigma of digital subjectivation. Who are the subjects of Big Data? A field where this question is particularly pressing is finance. Since the 1990s traders have been steadily integrated into computerized data assemblages, which calls for an ontology that eliminates the distinction between human sovereign subjects and non-human instrumental objects. The latter subjectivize traders in pre-conscious ways, because human consciousness runs too slow to follow the volatility of the market. In response to this conundrum Social Studies of Finance has drawn on Actor-Network Theory to interpret financial markets as technically constructed networks of human and non-human actors. I argue that in order to develop an explicitly critical data study it might be advantageous to refer to Maurizio Lazzarato’s theory of machinic subjugation instead. Although both accounts describe financial digital subjectivation similarly, Lazzarato has the advantage of coupling his description to a clear critique of and resistance to finance.

Ernesto Laclau and Critical Media Studies: Marxism, Capitalism, and Critique

DEFF Research Database (Denmark)

Schou, Jannick

2016-01-01

im-plications have been either overlooked or forgotten altogether. This paper seeks to reflect on the po-tentials and obstacles within Laclau’s work for critical media studies by engaging with the role of Marx-ism, capitalism and critique. First, the paper addresses the relation between Marxism...... and post-Marxism by arguing that rather than abandoning Marxism, Laclau actively situates his own work as a dialogue with and against this tradition. Second, the paper addresses the relation between Laclau’s analysis of so-called globalised capitalism and political struggle, which leads to a discussion...... and needs to receive further attention by future research. By providing an extended discussion of Laclau’s own work, this paper seeks to contribute to the critical application of discourse theory within the field of media studies and contribute to the on-going dialogue between Marxism, post-Marxism...

Effects of magnetic order on the superconducting length scales and critical fields in single crystal ErNi2B2C

DEFF Research Database (Denmark)

Gammel, P.L.; Barber, B.P.; Ramirez, A.P.

1999-01-01

The flux line form factor in small angle neutron scattering and transport data determines the superconducting length scares and critical fields in single crystal ErNi2B2C. For H parallel to c, the coherence length xi increases and the penetration depth lambda decreases when crossing T-N = 6.0 K......, the Neel transition. The critical fields show corresponding anomalies near T-N. For H perpendicular to c, the fourfold modulation of the upper critical field H-c2 is strongly temperature dependent, changing sign near T-N, and can be modeled using the anisotropy of the sublattice magnetization....

Education Studies: Issues & Critical Perspectives

Science.gov (United States)

Kassem, Derek; Mufti, Emmanuel; Robinson, John

2006-01-01

This major text for Education Studies students provides a critical account of key issues in education today. The text features: (1) A critical analysis of key issues in Education Studies to encourage students' thinking about education in the broadest terms; (2) Themed sections with introductions to link the issues discussed in each chapter; (3)…

Field, temperature, and angle dependent critical current density Jc(H,T,θ) in coated conductors obtained via contact-free methods

International Nuclear Information System (INIS)

Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C; Sinclair, J W; Chen Yimin; Selvamanickam, V

2010-01-01

Applications of coated conductors based on high- T c superconductors often require detailed knowledge of their critical current density J c as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J c using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

Quantum Criticality of an Ising-like Spin-1 /2 Antiferromagnetic Chain in a Transverse Magnetic Field

Science.gov (United States)

Wang, Zhe; Lorenz, T.; Gorbunov, D. I.; Cong, P. T.; Kohama, Y.; Niesen, S.; Breunig, O.; Engelmayer, J.; Herman, A.; Wu, Jianda; Kindo, K.; Wosnitza, J.; Zherlitsyn, S.; Loidl, A.

2018-05-01

We report on magnetization, sound-velocity, and magnetocaloric-effect measurements of the Ising-like spin-1 /2 antiferromagnetic chain system BaCo2V2O8 as a function of temperature down to 1.3 K and an applied transverse magnetic field up to 60 T. While across the Néel temperature of TN˜5 K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature the field-dependent measurements reveal a sharp softening of sound velocity v (B ) and a clear minimum of temperature T (B ) at B⊥c,3 D=21.4 T , indicating the suppression of the antiferromagnetic order. At higher fields, the T (B ) curve shows a broad minimum at B⊥c=40 T , accompanied by a broad minimum in the sound velocity and a saturationlike magnetization. These features signal a quantum phase transition, which is further characterized by the divergent behavior of the Grüneisen parameter ΓB∝(B -B⊥c)-1. By contrast, around the critical field, the Grüneisen parameter converges as temperature decreases, pointing to a quantum critical point of the one-dimensional transverse-field Ising model.

An extended approach for computing the critical properties in the two-and three-dimensional lattices within the effective-field renormalization group method

Science.gov (United States)

de Albuquerque, Douglas F.; Santos-Silva, Edimilson; Moreno, N. O.

2009-10-01

In this letter we employing the effective-field renormalization group (EFRG) to study the Ising model with nearest neighbors to obtain the reduced critical temperature and exponents ν for bi- and three-dimensional lattices by increasing cluster scheme by extending recent works. The technique follows up the same strategy of the mean field renormalization group (MFRG) by introducing an alternative way for constructing classical effective-field equations of state takes on rigorous Ising spin identities.

An extended approach for computing the critical properties in the two-and three-dimensional lattices within the effective-field renormalization group method

Energy Technology Data Exchange (ETDEWEB)

Albuquerque, Douglas F. de [Departamento de Matematica, Universidade Federal de Sergipe, 49100-000 Sao Cristovao, SE (Brazil)], E-mail: douglas@ufs.br; Santos-Silva, Edimilson [Departamento de Matematica, Universidade Federal de Sergipe, 49100-000 Sao Cristovao, SE (Brazil); Moreno, N.O. [Departamento de Fisica, Universidade Federal de Sergipe, 49100-000 Sao Cristovao, SE (Brazil)

2009-10-15

In this letter we employing the effective-field renormalization group (EFRG) to study the Ising model with nearest neighbors to obtain the reduced critical temperature and exponents {nu} for bi- and three-dimensional lattices by increasing cluster scheme by extending recent works. The technique follows up the same strategy of the mean field renormalization group (MFRG) by introducing an alternative way for constructing classical effective-field equations of state takes on rigorous Ising spin identities.

An extended approach for computing the critical properties in the two-and three-dimensional lattices within the effective-field renormalization group method

International Nuclear Information System (INIS)

Albuquerque, Douglas F. de; Santos-Silva, Edimilson; Moreno, N.O.

2009-01-01

In this letter we employing the effective-field renormalization group (EFRG) to study the Ising model with nearest neighbors to obtain the reduced critical temperature and exponents ν for bi- and three-dimensional lattices by increasing cluster scheme by extending recent works. The technique follows up the same strategy of the mean field renormalization group (MFRG) by introducing an alternative way for constructing classical effective-field equations of state takes on rigorous Ising spin identities.

Spin dynamics in the high-field phase of quantum-critical S =1/2 TlCuCl sub 3

CERN Document Server

Rueegg, C; Furrer, A; Krämer, K; Güdel, H U; Vorderwisch, P; Mutka, H

2002-01-01

An external magnetic field suppresses the spin-energy gap in singlet ground state S=1/2 TlCuCl sub 3. The system becomes quantum-critical at H sub c approx 5.7 T, where the energy of the lowest Zeeman-split triplet excitation crosses the nonmagnetic ground state. Antiferromagnetic ordering is reported above H sub c , which underlines the three-dimensional nature of the observed quantum phase transition. The intrinsic parameters of S=1/2 TlCuCl sub 3 allow us to access the critical region microscopically by neutron scattering. A substantial study of the spin dynamics in the high-field phase of TlCuCl sub 3 at T=1.5 K up to H=12 T was performed for the first time. The results possibly indicate two dynamical regimes, which can be understood within characteristically renormalized triplet modes and a low-lying dynamics of potentially collective origin. (orig.)

Theory of the upper critical field in antiferromagnetic superconductors

International Nuclear Information System (INIS)

Ro, C.; Levin, K.

1984-01-01

We compute the temperature T dependence of the upper critical field H/sub c/2(T) in antiferromagnetic (AF) superconductors. Using a strong-coupling formalism we explicitly treat the effects of the molecular field H/sub Q/, inelastic and elastic spin-fluctuation scattering and magnetic as well as nonmagnetic impurities. A sum rule is used to relate the T dependence of H/sub Q/ to that of the spin-fluctuation scattering. The decreased pair breaking observed below the Neel temperature in SmRh 4 B 4 and the increased pair breaking seen in the AF Chevrel compounds will both occur in our theory for a reasonable choice of parameters. For larger values of the dimensionless spin-exchange coupling constant N(0)J/sup c/f, spin-fluctuation-scattering effects dominate over those of H/sub Q/ and decreased pair breaking is observed below T/sub N/. For smaller values of the coupling constant, the converse is true. Impurity scattering is treated in a self-consistent fashion. As a consequence, the molecular field H/sub Q/ is altered by nonmagnetic impurities. This leads to important pair-breaking effects in H/sub c/2. A physical manifestation of this pair breaking is a qualitative change in the shape of the H/sub c/2 versus T curve, as nonmagnetic impurities are added. We give detailed predictions for the expected effects of these impurities on H/sub c/2 which can be tested experimentally

Influence of grain size and upper critical magnetic field on global pinning force of bronze-processed Nb/sub 3/Sn compound

International Nuclear Information System (INIS)

Ochiai, S.; Osamura, K.

1986-01-01

In order to know the dependency of global pinning force of Nb/sub 3/Sn compound on grain size and upper critical magnetic field, the global pinning force was measured at 3-15 T using bronze-processed multifilamentary composites. The grain size and upper critical magnetic field were varied by two types of annealing treatment: one is the isothermal annealing at 873, 973 and 1073 K up to 1730 ks and another is the two-stage annealing (low temperature annealing to form fine grains at 873 K for 1730 ks + high temperature annealing to raise upper critical magnetic field at 1073 K up to 18 ks). In the case of isothermal annealing treatment, both of grain size and upper critical magnetic field increased with increasing annealing temperature and time except for the annealing treatments at high temperature for prolonged times. In the case of two-stage annealing, both of them increased with second stage annealing time. The increase in grain size led to decrease in the pinning force but the increase in upper critical magnetic field to increase in it. From the analysis of the present data based on the Suenaga's speculation concerning with the density of pinning site and the Kramer's equation, it was suggested that the pinning force is, to a first approximation, proportional to the product of inverse grain size and (1-h)/sup 2/h/sup 1/2/ where h is the reduced magnetic field

Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5.

Science.gov (United States)

Ronning, F; Helm, T; Shirer, K R; Bachmann, M D; Balicas, L; Chan, M K; Ramshaw, B J; McDonald, R D; Balakirev, F F; Jaime, M; Bauer, E D; Moll, P J W

2017-08-17

Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn 5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at H c  ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

Critical Current Properties in Longitudinal Magnetic Field of YBCO Superconductor with APC

Science.gov (United States)

Kido, R.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Jha, A. K.; Matsumoto, K.

The critical current density (Jc) properties of the Artificial Pinning Center (APC) introduced YBa2Cu3O7 (YBCO) films in the longitudinal magnetic field were measured. Y2O3 or Y2BaCuO5 (Y211) was introduced as APCs to YBCO, and YBCO films with APC were fabricated on SrTiO3 single crystal substrate. The sizes of Y2O3 and Y211 were 5-10 nm and 10-20 nm, respectively. As a result, Jc enhancement in the longitudinal magnetic field was observed in Y2O3 introduced YBCO films. However, it was not observed in Y211 introduced YBCO films. Therefore, it was considered that Jc properties in the longitudinal magnetic field were affected by introducing of small size APC, and it was necessary that APC does not disturb the current pathway in the superconductor.

Upper Critical Field and de Haas-van Alphen Oscillations in KOs2O6 Measured in a Hybrid Magnet

Science.gov (United States)

Taichi Terashima,; Nobuyuki Kurita,; Atsushi Harada,; Kota Kodama,; Jun-ichi Yamaura,; Zenji Hiroi,; Hisatomo Harima,; Shinya Uji,

2010-08-01

Magnetic torque measurements have been performed on a KOs2O6 single crystal in magnetic fields up to 35.3 T and at temperatures down to 0.6 K. The upper critical field is determined to be ˜30 T. De Haas-van Alphen oscillations are observed. A large mass enhancement of (1+λ) = m* / mband = 7.6 is found. It is suggested that, for the large upper critical field to be reconciled with Pauli paramagnetic limiting, the observed mass enhancement must be of electron-phonon origin, including electron-rattling-mode interactions, for the most part.

Researching Critical Literacy: A Critical Study of Analysis of Classroom Discourse

Science.gov (United States)

Van Sluys, Katie; Lewison, Mitzi; Flint, Amy Seely

2006-01-01

Studying critical literacies includes examining how research practices influence what is learned about classroom activity and the world. This article highlights the processes and practices used in studying 1 classroom conversation. The data, drawn from an elementary school classroom of a Critical Literacy in Action teacher-researcher group member,…

Critical states and thermomagnetic instabilities in three-dimensional nanostructured superconductors

Energy Technology Data Exchange (ETDEWEB)

Tamegai, T., E-mail: tamegai@ap.t.u-tokyo.ac.jp [Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Mine, A.; Tsuchiya, Y.; Miyano, S.; Pyon, S. [Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Mawatari, Y.; Nagasawa, S.; Hidaka, M. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan)

2017-02-15

Highlights: • Critical state field profiles and thermomagnetic instabilities are studied in three-dimensional nanostructured superconductors. • We find that the critical state field profiles in bi-layer systems are not simple superpositions of critical states in the two layers. • We also studied flux avalanches in shifted strip arrays with layer numbers up to six. • Various forms of avalanches either perpendicular or parallel to the strip are observed when the overlap between layers is large. • We find that introduction of asymmetry to shifted strip arrays affects the shape of flux avalanches sensitively. - Abstract: Critical state field profiles and thermomagnetic instabilities are studied in two kinds of three-dimensional nanostructured superconductors. We find that the critical state field profiles in some simple bi-layer systems are not simple superpositions of critical states in the two layers. Competition between the divergence of the local field at the edges of the film and the shielding by the neighboring layer makes novel critical state field profiles. We also studied flux avalanches in shifted strip arrays (SSAs) with layer numbers up to six. Various forms of avalanches either perpendicular or parallel to the strip are observed when the overlap between strips in neighboring layers is large. We also find that introduction of asymmetry in various forms to SSA affects the shape of flux avalanches sensitively.

The Use of Critical Thinking in Social Science Textbooks of High School: A Field Study of Fars Province in Iran

Directory of Open Access Journals (Sweden)

Seyed Ahmad Hashemi

2011-01-01

Full Text Available This study aims at investigating the use of critical thinking in high school social science textbooks based on Fars Province teachers' attitudes in order to present a model for textbook development. To achieve this goal, the use of the following skills in the social science textbooks was analyzed: reasoning, questioning, assessment of examples and statements, group work, interpretation, true judgment about issues, analysis and evaluation, logicality, and explicitness. It is a field study which was conducted in several high schools of Fars Province in Iran. The population of this study included 568 social science teachers. The sample was selected based on the stratified random sampling procedure so that 153 teachers participated in this study. The data were collected using a forty-four-item questionnaire based on Likert-scale, which was developed and validated by the researcher himself and some experts. The reliability coefficient was also estimated as 0.86. The data were analyzed through descriptive statistics (frequency, percentage, standard deviation, and coefficient of variations and inferential statistics (Chi-square and Kruskal-Wallis Non-parametric tests. The result showed that the teachers of the Social Studies Textbook evaluated assessment of examples and statements, and analysis and evaluation skills as not satisfactory respectively. They evaluated the other skills as fairly satisfactory. Teachers of Sociology Textbook 1 evaluated explicitness, assessment of examples and statements, analysis and evaluation, and interpretation skills as not satisfactory respectively. They also evaluated other skills as fairly satisfactory. Teachers of Sociology Textbook 2 evaluated explicitness as not satisfactory, logicality as satisfactory, and other skills as fairly satisfactory. Therefore it is possible to rank order the social science textbooks of high school as satisfactory and not satisfactory with regard to the use of critical thinking. In other

Field-Induced Quantum Critical Point and Nodal Superconductivity in the Heavy-Fermion Superconductor Ce_{2}PdIn_{8}

Directory of Open Access Journals (Sweden)

J. K. Dong

2011-09-01

Full Text Available The in-plane resistivity ρ and thermal conductivity κ of the heavy-fermion superconductor Ce_{2}PdIn_{8} single crystals were measured down to 50 mK. A field-induced quantum critical point, occurring at the upper critical field H_{c2}, is demonstrated from the ρ(T∼T near H_{c2} and ρ(T∼T^{2} when further increasing the field. The large residual linear term κ_{0}/T at zero field and the rapid increase of κ(H/T at low field give evidence for nodal superconductivity in Ce_{2}PdIn_{8}. The jump of κ(H/T near H_{c2} suggests a first-order-like phase transition at low temperature. These results mimic the features of the famous CeCoIn_{5} superconductor, implying that Ce_{2}PdIn_{8} may be another interesting compound to investigate for the interplay between magnetism and superconductivity.

Flux pinning and critical current in layered type-II superconductors in parallel magnetic fields

International Nuclear Information System (INIS)

Prokic, V.; Davidovic, D.; Dobrosavljevic-Grujic, L.

1995-01-01

We have shown, within the Ginzburg-Landau theory, that the interaction between vortices and normal-metal layers in high-T c superconductor--normal-metal superlattices can cause high critical-current densities j c . The interaction is primarily magnetic, except at very low temperatures T, where the core interaction is dominant. For a lattice of vortices commensurate with an array of normal-metal layers in a parallel magnetic field H, strong magnetic pinning is obtained, with a nonmonotonic critical-current dependence on H, and with j c of the order of 10 7 --10 8 A/cm 2

Clinical Pharmacology Studies in Critically Ill Children

Science.gov (United States)

Thakkar, Nilay; Salerno, Sara; Hornik, Christoph P.; Gonzalez, Daniel

2016-01-01

Developmental and physiological changes in children contribute to variation in drug disposition with age. Additionally, critically ill children suffer from various life-threatening conditions that can lead to pathophysiological alterations that further affect pharmacokinetics (PK). Some factors that can alter PK in this patient population include variability in tissue distribution caused by protein binding changes and fluid shifts, altered drug elimination due to organ dysfunction, and use of medical interventions that can affect drug disposition (e.g., extracorporeal membrane oxygenation and continuous renal replacement therapy). Performing clinical studies in critically ill children is challenging because there is large inter-subject variability in the severity and time course of organ dysfunction; some critical illnesses are rare, which can affect subject enrollment; and critically ill children usually have multiple organ failure, necessitating careful selection of a study design. As a result, drug dosing in critically ill children is often based on extrapolations from adults or non-critically ill children. Dedicated clinical studies in critically ill children are urgently needed to identify optimal dosing of drugs in this population. This review will summarize the effect of critical illness on pediatric PK, the challenges associated with performing studies in this vulnerable subpopulation, and the clinical PK studies performed to date for commonly used drugs. PMID:27585904

Leading Critically: A Grounded Theory of Applied Critical Thinking in Leadership Studies

Science.gov (United States)

Jekins, Daniel M.; Cutchens, Amanda B.

2011-01-01

This study describes the development of a grounded theory of applied critical thinking in leadership studies and examines how student-centered experiential learning in leadership education bridged critical thinking with action. Over three semester undergraduate students in an upper level leadership studies course at a large four-year public…

Mean-field Ising crossover and the critical exponents γ, ν, and η for a polymer blend: d-PB/PS studied by small-angle neutron scattering

Science.gov (United States)

Janssen, S.; Schwahn, D.; Springer, T.

1992-05-01

The critical behavior of the polymer blend d-PB/PS was investigated by small-angle neutron scattering experiments. 3D Ising behavior was clearly observed with the critical exponents γ=1.26+/-0.01, ν=0.59+/-0.01, and η=0.047+/-0.004. The crossover to mean-field behavior occurs at T*=Tc+5.4 K. This is compared with the results of other experiments and the Landau-Ginzburg criterion. The Q dependence of the structure factor S(Q) follows the Ornstein-Zernike form in both regimes.

Influence of temperature on the critical in-plane field range for VBLs in the walls of hard domains

International Nuclear Information System (INIS)

Nie, X.F.; Guo, G.X.; Xu, J.P.; Liu, S.P.; Wang, L.N.; Huo, S.G.

2006-01-01

The influence of temperature on the critical in-plane field range for vertical Bloch lines in the walls of three kinds of hard domains is investigated experimentally. It is found that for each kind of three hard domains, there exists a critical in-plane field range, i. e. [H ip (1) (T),H ip (2) (T)], which depends on temperatures and in which vertical Bloch lines are unstable. Here, H ip (1) (T) is the initial critical in-plane field where VBLs in the walls of three kinds of hard domains are annihilated, and H ip (2) (T) is the lowest in-plane field where VBLs in their corresponding hard domains are annihilated completely. H ip (1) (T), H ip (2) (T) and [H ip (1) (T),H ip (2) (T)], all decrease as the temperature increase. Furthermore, H ip (1) (T) and H ip (2) (T) reach zero at T 0 1 and T 0 , respectively. In addition, there exists a relationship among them, when T is unchanged, H ip (1) (T) of the three kinds of hard domains (ordinary hard bubbles (OHB), first kind of dumbbell domain (ID) and second kind of dumbbell domains (IID)) decrease successively, and theirH ip (2) (T) are the same

The Emerging Field of Quantitative Blood Metabolomics for Biomarker Discovery in Critical Illnesses

Science.gov (United States)

Serkova, Natalie J.; Standiford, Theodore J.

2011-01-01

Metabolomics, a science of systems biology, is the global assessment of endogenous metabolites within a biologic system and represents a “snapshot” reading of gene function, enzyme activity, and the physiological landscape. Metabolite detection, either individual or grouped as a metabolomic profile, is usually performed in cells, tissues, or biofluids by either nuclear magnetic resonance spectroscopy or mass spectrometry followed by sophisticated multivariate data analysis. Because loss of metabolic homeostasis is common in critical illness, the metabolome could have many applications, including biomarker and drug target identification. Metabolomics could also significantly advance our understanding of the complex pathophysiology of acute illnesses, such as sepsis and acute lung injury/acute respiratory distress syndrome. Despite this potential, the clinical community is largely unfamiliar with the field of metabolomics, including the methodologies involved, technical challenges, and, most importantly, clinical uses. Although there is evidence of successful preclinical applications, the clinical usefulness and application of metabolomics in critical illness is just beginning to emerge, the advancement of which hinges on linking metabolite data to known and validated clinically relevant indices. In addition, other important aspects, such as patient selection, sample collection, and processing, as well as the needed multivariate data analysis, have to be taken into consideration before this innovative approach to biomarker discovery can become a reliable tool in the intensive care unit. The purpose of this review is to begin to familiarize clinicians with the field of metabolomics and its application for biomarker discovery in critical illnesses such as sepsis. PMID:21680948

Moving forward: response to "Studying eyewitness investigations in the field".

Science.gov (United States)

Ross, Stephen J; Malpass, Roy S

2008-02-01

Field studies of eyewitness identification are richly confounded. Determining which confounds undermine interpretation is important. The blind administration confound in the Illinois study is said to undermine it's value for understanding the relative utility of simultaneous and sequential lineups. Most criticisms of the Illinois study focus on filler identifications, and related inferences about the importance of the blind confound. We find no convincing evidence supporting this line of attack and wonder at filler identifications as the major line of criticism. More debilitating problems impede using the Illinois study to address the simultaneous versus sequential lineup controversy: inability to estimate guilt independent of identification evidence, lack of protocol compliance monitoring, and assessment of lineups quality. Moving forward requires removing these limitations.

Bourdieu's Habitus and Field: Implications on the Practice and Theory of Critical Action Learning

Science.gov (United States)

Warwick, Rob; McCray, Janet; Board, Douglas

2017-01-01

This paper considers the logic of practice of the French sociologist Pierre Bourdieu in relation to critical action learning: in particular "habitus" which is co-created with field and the interplay amongst the two in the form of misrecognition and risk. We draw on interviews with participants who have experienced action learning as part…

Integrating Emotions Into the Critical Interpretive Synthesis.

Science.gov (United States)

McFerran, Katrina Skewes; Hense, Cherry; Medcalf, Laura; Murphy, Melissa; Fairchild, Rebecca

2017-01-01

Critical interpretive synthesis is a particular form of systematic review that critically examines the decisions made by authors while conducting and publishing about their research and practices. It differs from empirical syntheses of qualitative research by emphasizing the interpreted and constructed nature of this form of secondary analysis. In this article, we extend previous literature on critical interpretive syntheses by highlighting the integration of emotional responses when developing critical questions for interrogating the literature and interpreting results. Our extension of the critical interpretive synthesis is illustrated through examples from five studies examining literature in our own field of music therapy, as well as related fields of disability studies, mental health, music psychology, and child welfare. The methodology we have refined uses an iterative and recursive method that promotes increased critical awareness of the assumptions driving the production of research in health contexts. © The Author(s) 2016.

The exponential critical state of high-Tc ceramics

International Nuclear Information System (INIS)

Castro, H.; Rinderer, L.

1994-01-01

The critical current in high-Tc materials is strongly reduced by a magnetic field. We studied this dependency for tubular YBCO samples. We find an exponential drop as the field is increased from zero up to some tens of oersted. This behavior was already observed by others, however little work has been done in this direction. We define what we call the ''exponential critical state'' of HTSC and compare the prediction for the magnetization with experimental data. Furthermore, the ''Kim critical state'' is obtained as the small field limit. (orig.)

Criticality safety basics, a study guide

Energy Technology Data Exchange (ETDEWEB)

V. L. Putman

1999-09-01

This document is a self-study and classroom guide, for criticality safety of activities with fissile materials outside nuclear reactors. This guide provides a basic overview of criticality safety and criticality accident prevention methods divided into three parts: theory, application, and history. Except for topic emphasis, theory and history information is general, while application information is specific to the Idaho National Engineering and Environmental Laboratory (INEEL). Information presented here should be useful to personnel who must know criticality safety basics to perform their assignments safely or to design critically safe equipment or operations. However, the guide's primary target audience is fissile material handler candidates.

Criticality safety basics, a study guide

International Nuclear Information System (INIS)

Putman, V.L.

1999-01-01

This document is a self-study and classroom guide, for criticality safety of activities with fissile materials outside nuclear reactors. This guide provides a basic overview of criticality safety and criticality accident prevention methods divided into three parts: theory, application, and history. Except for topic emphasis, theory and history information is general, while application information is specific to the Idaho National Engineering and Environmental Laboratory (INEEL). Information presented here should be useful to personnel who must know criticality safety basics to perform their assignments safely or to design critically safe equipment or operations. However, the guide's primary target audience is fissile material handler candidates

Comparison study of toroidal-field divertors for a compact reversed-field pinch reactor

International Nuclear Information System (INIS)

Bathke, C.G.; Krakowski, R.A.; Miller, R.L.

1985-01-01

Two divertor configurations for the Compact Reversed-Field Pinch Reactor (CRFPR) based on diverting the minority (toroidal) field have been reported. A critical factor in evaluating the performance of both poloidally symmetric and bundle divertor configurations is the accurate determination of the divertor connection length and the monitoring of magnetic islands introduced by the divertors, the latter being a three-dimensional effect. To this end the poloidal-field, toroidal-field, and divertor coils and the plasma currents are simulated in three dimensions for field-line tracings in both the divertor channel and the plasma-edge regions. The results of this analysis indicate a clear preference for the poloidally symmetric toroidal-field divertor. Design modifications to the limiter-based CRFPR design that accommodate this divertor are presented

The critical current density of an SNS Josephson-junction in high magnetic fields

International Nuclear Information System (INIS)

Carty, George J; Hampshire, Damian P

2013-01-01

Although the functional form of the critical current density (J c ) of superconducting–normal–superconducting (SNS) Josephson-junctions (J-Js) has long been known in the very low field limit (e.g. the sinc function), includes the local properties of the junction and has been confirmed experimentally in many systems, there have been no such general solutions available for high fields. Here, we derive general analytic equations for J c in zero field and in high fields across SNS J-Js for arbitrary resistivity of the superconductor and the normal layer which are consistent with the literature results available in limiting cases. We confirm the validity of the approach using both computational solutions to time-dependent Ginzburg–Landau (TDGL) theory applied to SNS junctions and experimental J c data for an SNS PbBi–Cd–PbBi junction. We suggest that since SNS junctions can be considered the basic building blocks for the description of the grain boundaries of polycrystalline materials because they both provide flux-flow channels, this work may provide a mathematical framework for high J c technological polycrystalline superconductors in high magnetic fields. (paper)

Proposal for the risk management implementation phase in oil field development project by adding value on the refurbishment of critical equipment

Directory of Open Access Journals (Sweden)

Hamid Abdul

2017-01-01

Full Text Available Refurbishment process is a conceptual stage in product life cycle. It is utilized in existing equipment in the field by adding value to recondition and repaired equipment. The main interest of this paper is to implement and design risk management implementation phase in oil field development project on the refurbishment of critical equipment in oil and gas industry. This paper is provided base on research and experiences in risk management and learned from practical team in industry which matched by an application in oil field development project in refurbishment of critical equipment. A framework of implementation phase for risk management in oil field development project in refurbishment critical equipment were reviewed and added value on communication skills of the project team to the stakeholder and organization, which support to external body and vice-versa. Risk management framework can be used for reference of refurbishment process with simply process and developed with same concept for the next wide development project in industry.

Upper critical magnetic field of superconducting films with magnetic impurities

International Nuclear Information System (INIS)

Lemberger, T.R.

1978-01-01

The upper critical magnetic field, H/sub c2/(T), of In-Mn and Pb-Mn alloy films was measured. H/sub c2/ was determined from the resistance of the films. The results were compared with the theory of Fulde and Maki. This theory assumes that the electron-phonon coupling is weak, and that the interaction between the impurity spins and the conduction electron spins is weak. The theory predicts that the pair-breaking effect of the magnetic impurities is temperature-independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. Furthermore, it predicts explicitly the temperature dependence of H/sub c2/. The temperature dependence of H/sub c2/ for the In-Mn alloy films is well described by the Fulde-Maki theory, despite the moderately strong electron-phonon coupling and the strong interaction between the impurity spins and the conduction electron spins. The temperature dependence of H/sub c2/ for the Pb-Mn alloy films is not well described by the Fulde-Maki theory, probably due to the strong electron-phonon coupling in Pb. However, even without a quantitatively correct theory, one can conclude from the Pb-Mn data that the pair-breaking effect of the magnetic impurities is temperature independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. For some of the Pb-Mn alloy films, there was a region of positive curvature in H/sub c2/(T) near the zero-field transition temperature. This positive curvature is not understood

Critical dynamics a field theory approach to equilibrium and non-equilibrium scaling behavior

CERN Document Server

Täuber, Uwe C

2014-01-01

Introducing a unified framework for describing and understanding complex interacting systems common in physics, chemistry, biology, ecology, and the social sciences, this comprehensive overview of dynamic critical phenomena covers the description of systems at thermal equilibrium, quantum systems, and non-equilibrium systems. Powerful mathematical techniques for dealing with complex dynamic systems are carefully introduced, including field-theoretic tools and the perturbative dynamical renormalization group approach, rapidly building up a mathematical toolbox of relevant skills. Heuristic and qualitative arguments outlining the essential theory behind each type of system are introduced at the start of each chapter, alongside real-world numerical and experimental data, firmly linking new mathematical techniques to their practical applications. Each chapter is supported by carefully tailored problems for solution, and comprehensive suggestions for further reading, making this an excellent introduction to critic...

Developing critical thinking through Socratic Questioning: An Action Research Study

Directory of Open Access Journals (Sweden)

Husniah Sahamid

2016-07-01

Full Text Available An action research study was conducted among 24 Form 4 level Malaysian students, aged 16. The duration of the study was five months and constituted 16 one-hour literature lessons (short stories from the secondary level Malaysian English Language Upper Secondary Level school syllabus. This paper describes my experience as a teacher-as-researcher to assist students to respond to teacher questions through Paul’s (1993 model of Socratic Questioning which claims to develop students’ critical thinking. Data was collected through researcher’s field notes, students’ writing tasks and student interviews which were analysed after each cycle of the action research study. Changes and adaptations were consequently made based on the data collected and upon teacher reflection to improve practice. The results of this study indicate that repeated practice of Socratic Questioning had a positive effect on student responses and writing tasks. Some of the factors affecting students’ performance included students’ language proficiency, weak reading ability and students’ anxiety towards the questioning method. These issues had to be addressed and dealt with, before Socratic Questioning could be properly implemented in the classroom. Keywords: Socratic questioning, teacher questioning, critical thinking, action research

Effective field approach to the Ising film in a transverse field

International Nuclear Information System (INIS)

Peliti, L.; Saber, M.

1998-05-01

Within the framework of the effective field theory, we examine the phase transitions of the spin -1/2 Ising film in a transverse field. We study the critical temperature of the film as a function of the exchange interactions, the transverse field and the film thickness. We find that, if the ratio of the surface exchange interactions to the bulk ones R=J s /J is smaller that a critical value R c , the critical temperature T c /J of the film is smaller that the bulk critical temperature T B c /J and as R is increased further, T c /J approaches T B c /J. On the other hand, if R>R c ,T c /J is larger than the bulk T B c /J and the surface T S c /J critical temperatures of the corresponding semi-infinite system and as R is increased further, T c /J approaches the surface critical temperature T S c /J. (author)

Optical Studies of Pure Fluids about Their Critical Points

Science.gov (United States)

Pang, Kian Tiong

Three optical experiments were performed on pure fluids near their critical points. In the first two setups, CH_3F and H_2C:CF _2 were each tested in a temperature -controlled, prism-shaped cell and a thin parallel-windows cell. In the prism cell, a laser beam was additionally deflected by the fluid present. From the deflection data, the refractive index was related to the density to find the Lorentz-Lorenz function. Critical temperature (T _{c}), density, refractive index and electronic polarizability were found. In the second experiment, a critically-filled, thin parallel-windows cell was placed in one arm of a Mach-Zehnder interoferometer. Fluid density was monitored by changes in the fringe pattern with changing cell temperature. The aim was to improve on the precision of T_{c}: T_{c}{rm (CH}_3 F) = (44cdot9087 +/- 0cdot0002)C; T _{c}{rm(H}_2C:CF _2) = (29cdot7419 +/- 0cdot0001)C; and, to study the coexistence curve and diameter as close to T_{c} as possible. The critical behaviour was compared to the theoretical renormalization group calculations. The derived coefficients were tested against a proposed three-body interaction to explain the field-mixing term in the diameter near the critical point. It was found that H_2C:CF_2 behaved as predicted by such an interaction; CH _3F (and CHF_3) did not. The third experiment was a feasibility study to find out if (critical) isotherms could be measured optically in a setup which combined the prism and parallel-windows cells. The aim was to map isotherms in as wide a range of pressure and density as possible and to probe the critical region directly. Pressure was monitored by a precise digital pressure gauge. CH_3F and CHF _3 were tested in this system. It was found that at low densities, the calculated second and third virial coefficients agreed with reference values. However, the data around the critical point were not accurate enough for use to calculate the critical exponent, delta . The calculated value was

Criticality safety (prospect of study in NUCEF)

International Nuclear Information System (INIS)

Itagaki, Masafumi

1996-01-01

Experimental studies of criticality safety are under way using STACY and TRACY in NUCEF. Collection of fundamental data on criticality in a solution system is undergoing with STACY to confirm that the likelihood of criticality safety in the system constructed on the assumption of apparatuses in a reprocessing plant is enough large. Whereas some experiments simulating criticality accidents in a reprocessing plant using TRACY were designed to investigate the behaviors of fuel solution and radioactive matters in order to clarify whether it is possible to safely shut them in the facility even if a critical accident occurs. Both STACY and TRACY reached the criticality in 1995. Up to now a series of criticality experiments have been done using STACY with a core tank φ60 cm and the first periodical examination is now under way. On the other hand, we have a plan using TRACY to investigate the behaviors of nuclear heat solution at a criticality accident, and the releasing, transfer and deposition of radioactive materials. After reaching the criticality for the first, the performance verification test has been conducted. The full-scale study using TRACY is planned to begin in the second half of 1996. (M.N.)

Critical and Griffiths-McCoy singularities in quantum Ising spin glasses on d -dimensional hypercubic lattices: A series expansion study

Science.gov (United States)

Singh, R. R. P.; Young, A. P.

2017-08-01

We study the ±J transverse-field Ising spin-glass model at zero temperature on d -dimensional hypercubic lattices and in the Sherrington-Kirkpatrick (SK) model, by series expansions around the strong-field limit. In the SK model and in high dimensions our calculated critical properties are in excellent agreement with the exact mean-field results, surprisingly even down to dimension d =6 , which is below the upper critical dimension of d =8 . In contrast, at lower dimensions we find a rich singular behavior consisting of critical and Griffiths-McCoy singularities. The divergence of the equal-time structure factor allows us to locate the critical coupling where the correlation length diverges, implying the onset of a thermodynamic phase transition. We find that the spin-glass susceptibility as well as various power moments of the local susceptibility become singular in the paramagnetic phase before the critical point. Griffiths-McCoy singularities are very strong in two dimensions but decrease rapidly as the dimension increases. We present evidence that high enough powers of the local susceptibility may become singular at the pure-system critical point.

Quench dynamics across quantum critical points

International Nuclear Information System (INIS)

Sengupta, K.; Powell, Stephen; Sachdev, Subir

2004-01-01

We study the quantum dynamics of a number of model systems as their coupling constants are changed rapidly across a quantum critical point. The primary motivation is provided by the recent experiments of Greiner et al. [Nature (London) 415, 39 (2002)] who studied the response of a Mott insulator of ultracold atoms in an optical lattice to a strong potential gradient. In a previous work, it had been argued that the resonant response observed at a critical potential gradient could be understood by proximity to an Ising quantum critical point describing the onset of density wave order. Here we obtain numerical results on the evolution of the density wave order as the potential gradient is scanned across the quantum critical point. This is supplemented by studies of the integrable quantum Ising spin chain in a transverse field, where we obtain exact results for the evolution of the Ising order correlations under a time-dependent transverse field. We also study the evolution of transverse superfluid order in the three-dimensional case. In all cases, the order parameter is best enhanced in the vicinity of the quantum critical point

Experimental Study of Thermal Field Evolution in the Short-Impending Stage Before Earthquakes

Science.gov (United States)

Ren, Yaqiong; Ma, Jin; Liu, Peixun; Chen, Shunyun

2017-08-01

Phenomena at critical points are vital for identifying the short-impending stage prior to earthquakes. The peak stress is a critical point when stress is converted from predominantly accumulation to predominantly release. We call the duration between the peak stress and instability "the meta-instability stage", which refers to the short-impending stage of earthquakes. The meta-instability stage consists of a steady releasing quasi-static stage and an accelerated releasing quasi-dynamic stage. The turning point of the above two stages is the remaining critical point. To identify the two critical points in the field, it is necessary to study the characteristic phenomena of various physical fields in the meta-instability stage in the laboratory, and the strain and displacement variations were studied. Considering that stress and relative displacement can be detected by thermal variations and peculiarities in the full-field observations, we employed a cooled thermal infrared imaging system to record thermal variations in the meta-instability stage of stick slip events generated along a simulated, precut planer strike slip fault in a granodiorite block on a horizontally bilateral servo-controlled press machine. The experimental results demonstrate the following: (1) a large area of decreasing temperatures in wall rocks and increasing temperatures in sporadic sections of the fault indicate entrance into the meta-instability stage. (2) The rapid expansion of regions of increasing temperatures on the fault and the enhancement of temperature increase amplitude correspond to the turning point from the quasi-static stage to the quasi-dynamic stage. Our results reveal thermal indicators for the critical points prior to earthquakes that provide clues for identifying the short-impending stage of earthquakes.

Critical-state model for the determination of critical currents in disk-shaped superconductors

International Nuclear Information System (INIS)

Frankel, D.J.

1979-01-01

A series of experiments has been carried out on the flux trapping and shielding capabilities of a flat strip of Nb-Ti/Cu composite material. A circular piece of material from the strip was tested in a uniform field directed perpendicularly to the surface of the sample. Profiles of the normal component of the field along the sample diameter were measured. The critical-state model was adapted for this geometry and proved capable of reproducing the measured field profiles. Model curves agreed well with experimental field profiles generated when the full sample was in the critical state, when only a portion of the sample was in the critical state, and when profiles were obtained after the direction of the rate change of the magnetic field was reversed. The adaption of the critical-state model to disk geometry provides a possible method either to derive values of the critical current from measurements of field profiles above thin flat samples, or to predict the trapping and shielding behavior of such samples if the critical current is already known. This method of determining critical currents does not require that samples be formed into narrow strips or wires, as is required for direct measurements of J/sub c/, or into tubes or cylinders, as is usually required for magnetization-type measurements. Only a relatively small approximately circular piece of material is needed. The method relies on induced currents, so there is no need to pass large currents into the sample. The field-profile measurements are easily performed with expensive Hall probes and do not require detection of the resistive transition of the superconductor

Critical Security Studies in the 21st Century: Any Directions for Lithuanian Security Studies?

Directory of Open Access Journals (Sweden)

Jakniūnaitė Dovilė

2014-12-01

Full Text Available This article focuses on recent developments and discussions in the field of security studies and aims to suggest new guidelines for the research of Lithuanian security policy. First it covers the main subjects of contemporary security discourse; next it provides evaluation and review of the critical tradition in security studies that frames presuppositions and is the means for analyzing specific security issues as well as that which fosters reflexive thinking about security. The third part deals with three topics of security research (analysis of security through the concepts of risk, exceptionality and media which have become talking-points in recent years and which have provided innovative insights in security studies.

Kiloampere, Variable-Temperature, Critical-Current Measurements of High-Field Superconductors.

Science.gov (United States)

Goodrich, L F; Cheggour, N; Stauffer, T C; Filla, B J; Lu, X F

2013-01-01

K to those measured on the same specimen in flowing helium gas ("gas" or I c gas) at the same temperature. These comparisons indicate the temperature control is effective over the superconducting wire length between the voltage taps, and this condition is valid for all types of sample investigated, including Nb-Ti, Nb3Sn, and MgB2 wires. The liquid/gas comparisons are used to study the variable-temperature measurement protocol that was necessary to obtain the "correct" critical current, which was assumed to be the I c liq. We also calibrated the magnetoresistance effect of resistive thermometers for temperatures from 4 K to 35 K and magnetic fields from 0 T to 16 T. This calibration reduces systematic errors in the variable-temperature data, but it does not affect the liquid/gas comparison since the same thermometers are used in both cases.

Enhancing students’ critical thinking skills through critical thinking assessment in calculus course

Science.gov (United States)

Zulfaneti; Edriati, S.; Mukhni

2018-01-01

This study aims to determine the development of students’ critical thinking skills through the implementation of critical thinking instruments in Calculus lectures. The instruments consist of observation sheets, critical thinking test, self-assessment, peer assessment and portfolio. The research was a qualitative research; with the participants were 53 first-year students who take Integral Calculus in Mathematics Education Department STKIP PGRI Sumatera Barat representing high-ability students, medium and low. The data in this study were collected by tests, interviews, observations and field notes. Data were analyzed descriptively; data reduction, data presentation, and conclusions. For testing the validity of data, it was used credibility test data by increasing persistence and triangulation. The results showed that in high-level students there is a change of ability from Critical enough to be Very Critical, in the students with moderate and low ability there is a change of ability from Uncritical to Critical. So it can be concluded that the assessment instruments have a good contribution and can improve the ability of critical thinking.

Critical Curriculum Studies: Education, Consciousness, and the Politics of Knowing. Critical Social Thought

Science.gov (United States)

Au, Wayne

2011-01-01

"Critical Curriculum Studies" offers a novel framework for thinking about how curriculum relates to students' understanding of the world around them. Wayne Au brings together curriculum theory, critical educational studies, and feminist standpoint theory with practical examples of teaching for social justice to argue for a transformative…

Effect of external magnetic field on critical current for the onset of virtual cathode oscillations in relativistic electron beams

International Nuclear Information System (INIS)

Hramov, Alexander; Koronovskii, Alexey; Morozov, Mikhail; Mushtakov, Alexander

2008-01-01

In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [D.J. Sullivan, J.E. Walsh, E. Coutsias, in: V.L. Granatstein, I. Alexeff (Eds.), Virtual Cathode Oscillator (Vircator) Theory, in: High Power Microwave Sources, vol. 13, Artech House Microwave Library, 1987, Chapter 13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields

Disorder and the upper critical field of Nb3Ge

International Nuclear Information System (INIS)

Habermeier, H.U.

1981-01-01

The upper critical field, H/sub c2/, as determined from experimental values of T/sub c/ and (dH/sub c2//dT)/sub Tc/, has been investigated in Nb 3 Ge superconducting thin films with different degree of structural disorder. An increase of H/sub c2/(O) up to 36.9 T was found for samples with resistivities ranging from 40 to 60 /mu/sub/ OMEGA/cm and a decrease of H/sub c2/(O) to 5.7 T for /rho/.150 /mu/sub/ OMEGA/cm. Based on the Ginsburg-Landau solution for H/sub c2/(O) and the change of the coherence length with the electron mean free path a model is presented which describes the change of H/sub c2/(O) with resistivity, qualitatively. 15 refs

Field, temperature, and angle dependent critical current density J{sub c}(H,T,{theta}) in coated conductors obtained via contact-free methods

Energy Technology Data Exchange (ETDEWEB)

Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6092 (United States); Sinclair, J W [Department of Physics, University of Tennessee, Knoxville, TN 37996-1200 (United States); Chen Yimin; Selvamanickam, V [SuperPower, Incorporated, 450 Duane Avenue, Schenectady, NY 12304 (United States)

2010-01-15

Applications of coated conductors based on high- T{sub c} superconductors often require detailed knowledge of their critical current density J{sub c} as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J{sub c} using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

Critical current in nonhomogeneous YBCO coated conductors

International Nuclear Information System (INIS)

Rostila, L; Mikkonen, R; Lehtonen, J

2008-01-01

The critical current of an YBCO tape is determined by the magnetic field inside the YBCO layer and the quality of YBCO material. In thick YBCO layers the average critical current density is reduced by the self-field and decreased material quality. In this paper the combined influence of the material nonhomogeneities and self-field on the critical current of YBCO tapes is scrutinised. First, the zero field critical current density was assumed to decrease along the YBCO thickness. Secondly, the possible defects created in the cutting of YBCO tapes were modelled as a function of lowered critical current density near the tape edges. In both cases the critical current was computed numerically with integral element method. The results suggest that the variation of zero field critical current density, J c0 , along the tape thickness does not effect on the critical current if the mean value of J c0 is kept constant. However, if J c0 is varied along the tape width the critical current can change due to the variated self-field. The computations can be used to determine when it is possible to evaluate the average zero field critical current density from a voltage-current measurement with an appropriate accuracy

The Crisis of Critique in Critical Management Studies

DEFF Research Database (Denmark)

Lystbæk, Christian Tang

both directions and employ both conceptions in their critique. Critique should not ignore one of the dual aims. Hence, my paper will point toward a Third Wave of critical management studies, addressing the question (or quest) whether the fundamental tension between Normativity and Contextuality can......Generally speaking, critical management studies are based upon a critique of customary conceptions of management for being reductionist and carrying implicit, unrecognized (problematic) assumptions. This conceptual paper argues, however, that this holds for critical management studies too: Critical...... management studies are equally based upon reductionist, problematic assumptions regarding the conception of, not management, but critique. Thus, this paper identifies a crisis in critical management studies in terms of simplified accounts of critique. There has been and still is a rough dividing line between...

Upper critical field measurements in high-Tc superconducting oxides

Science.gov (United States)

Ousset, J. C.; Bobo, J. F.; Ulmet, J. P.; Rakoto, H.; Cheggour, N.

We present upper critical field measurements on the superconducting oxides RE Ba2Cu3O7-δ (RE = Y, Gd) performed in a pulsed magnetic field up to 43 T. Values for Hc2 as high as 52 T and 77 T for Y and Gd respectively, are expected at 77 K. However, in order to observe no resistive behaviour up to 43 T the temperature must be decreased down to 50 K. In the case of oxygen deficient systems the magnetoresistance reveals two superconducting phases wich could be related to two different orders of oxygen vacancies. Nous présentons des mesures de champ critique Hc2 sur les supraconducteurs TR Ba 2Cu3O7-δ (TR = Y, Gd) réalisées en champ magnétique pulsé jusqu'à 43 T. Elles permettent de prévoir des valeurs de H c2 de 52 T et 77 T respectivement pour Y et Gd à 77 K. Cependant, pour ne pas observer de comportement résistif jusqu'au champ maximum, il est nécessaire de refroidir l'échantillon jusqu'à 50 K. Dans le cas des systèmes déficients en oxygène (δ important) nous mettons en évidence l'existence de deux phases supraconductrices qui pourraient être dues à deux ordres différents des lacunes d'oxygène.

Critical Phenomena Associated with Boson Stars

OpenAIRE

Hawley, Scott H.; Choptuik, Matthew W.

2001-01-01

We present a brief synopsis of related work (gr-qc/0007039), describing a study of black hole threshold phenomena for a self-gravitating, massive complex scalar field in spherical symmetry. We construct Type I critical solutions dynamically by tuning a one-parameter family of initial data consisting of a boson star and a massless real scalar field, and numerically evolving this data. The resulting critical solutions appear to correspond to boson stars on the unstable branch, as we show via co...

Dynamic trapping near a quantum critical point

Science.gov (United States)

Kolodrubetz, Michael; Katz, Emanuel; Polkovnikov, Anatoli

2015-02-01

The study of dynamics in closed quantum systems has been revitalized by the emergence of experimental systems that are well-isolated from their environment. In this paper, we consider the closed-system dynamics of an archetypal model: spins driven across a second-order quantum critical point, which are traditionally described by the Kibble-Zurek mechanism. Imbuing the driving field with Newtonian dynamics, we find that the full closed system exhibits a robust new phenomenon—dynamic critical trapping—in which the system is self-trapped near the critical point due to efficient absorption of field kinetic energy by heating the quantum spins. We quantify limits in which this phenomenon can be observed and generalize these results by developing a Kibble-Zurek scaling theory that incorporates the dynamic field. Our findings can potentially be interesting in the context of early universe physics, where the role of the driving field is played by the inflaton or a modulus field.

Our Prospective Mathematic Teachers Are Not Critical Thinkers Yet

Science.gov (United States)

As'ari, Abdur Rahman; Mahmudi, Ali; Nuerlaelah, Elah

2017-01-01

In order to help students develop their critical thinking skills, teachers need to model the critical thinking skills and dispositions in front of their students. Unfortunately, very rare studies investigating prospective teachers' readiness in critical thinking dispositions are available in the field of mathematics education. This study was…

Planning and setting objectives in field studies: Chapter 2

Science.gov (United States)

Fisher, Robert N.; Dodd, C. Kenneth

2016-01-01

This chapter enumerates the steps required in designing and planning field studies on the ecology and conservation of reptiles, as these involve a high level of uncertainty and risk. To this end, the chapter differentiates between goals (descriptions of what one intends to accomplish) and objectives (the measurable steps required to achieve the established goals). Thus, meeting a specific goal may require many objectives. It may not be possible to define some of them until certain experiments have been conducted; often evaluations of sampling protocols are needed to increase certainty in the biological results. And if sampling locations are fixed and sampling events are repeated over time, then both study-specific covariates and sampling-specific covariates should exist. Additionally, other critical design considerations for field study include obtaining permits, as well as researching ethics and biosecurity issues.

The nature of transport critical current hysteresis in HTSC: magnetic fields and high pressures. [Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Svistunov, V M; Yachenko, A.I. d' ; Tarenkov, V Yu [Donetsk Physico-Technical Inst., Ukrainian SSR (USSR)

1991-12-01

It was found that pressure has a strong influence on the critical current hysteresis loop of ceramics at H {proportional to} 10 kOe. The phenomenon is attributed to the critical current hysteresis of separate Josephson contacts and is due to the Abrikosov vortex density gradient within granules. The gradient defines both the sign and the value of the pinning current, whereas the sign of Meissner reversible surfaces current component is determined by the external field H direction. As a result the critical current of Josephson contacts defined by the total surface value depends on the magnetic prehistory of a sample. (orig.).

Critical fields and growth rates of the Tayler instability as probed by a columnar gallium experiment

OpenAIRE

Ruediger, Guenther; Gellert, Marcus; Schultz, Manfred; Strassmeier, Klaus G.; Stefani, Frank; Gundrum, Thomas; Seilmayer, Martin; Gerbeth, Gunter

2012-01-01

Many astrophysical phenomena (such as the slow rotation of neutron stars or the rigid rotation of the solar core) can be explained by the action of the Tayler instability of toroidal magnetic fields in the radiative zones of stars. In order to place the theory of this instability on a safe fundament it has been realized in a laboratory experiment measuring the critical field strength, the growth rates as well as the shape of the supercritical modes. A strong electrical current flows through a...

International critical perspectives

NARCIS (Netherlands)

Sambrook, S.A.; Poell, R.F.

2014-01-01

The Problem Critical perspectives on human resource development (HRD) have emerged, across Europe and America, hailed as the future of the field. However, we note the paucity of critical perspectives globally, the problematic dominance of critical HRD activities in Western sites of theory and

Critical heat flux of forced convection boiling in an oscilating acceleration field. Pt. 1

International Nuclear Information System (INIS)

Otsuji, T.; Kurosawa, A.

1982-01-01

The influence of periodically varying acceleration on critical heat flux (CHF) of Freon-113 flowing upward in a uniformly heated vertical annular channel has been studied experimentally. The freon loop was oscillated vertically to determine the ratio of CHF in the oscillating acceleration field to the corresponding stationary value. The amplitude of inlet flow oscillation induced by variation of acceleration, which causes early CHF, is proportional to the acceleration amplitude. The dependence of inlet flow rate on the oscillating acceleration decreases with increasing inlet subcooling, and no oscillation of inlet flow is observed in the case of negative exit quality (subcooled boiling). Nevertheless the degradation of CHF is more remarkable in the low quality region. This result suggests the necessity to introduce an other mechanism of early CHF than flow oscillation. (orig.)

Critical cyberculture studies

CERN Document Server

Silver, David; Jones, Steve

2006-01-01

Starting in the early 1990s, journalists and scholars began responding to and trying to take account of new technologies and their impact on our lives. By the end of the decade, the full-fledged study of cyberculture had arrived. Today, there exists a large body of critical work on the subject, with cutting-edge studies probing beyond the mere existence of virtual communities and online identities to examine the social, cultural, and economic relationships that take place online. Taking stock of the exciting work that is being done and positing what cyberculture's future might look like, Criti

(Critical) Language Awareness in Business Communication

Science.gov (United States)

Weninger, Csilla; Kan, Katy Hoi-Yi

2013-01-01

In the last 20 years, critical approaches to language and literacy education have established themselves as an academic field, with an abundance of empirical studies applying Critical Literacy principles in classes and curricula at schools and universities. Noticeably absent from the contexts of implementation are courses in Business English and…

Critical pressure of non-equilibrium two-phase critical flow

Energy Technology Data Exchange (ETDEWEB)

Minzer, U [Israel Electric Corp. Ltd., Haifa (Israel)

1996-12-01

Critical pressure is defined as the pressure existing at the exit edge of the piping, when it remains constant despite a decrease in the back. According to this definition the critical pressure is larger than the back pressure and for two-phase conditions below saturation pressure. The two-phase critical pressure has a major influence on the two-phase critical flow characteristics. Therefore it is of High significance in calculations of critical mass flux and critical depressurization rate, which are important in the fields of Nuclear Reactor Safety and Industrial Safety. At the Nuclear Reactor Safety field is useful for estimations of the Reactor Cooling System depressurization, the core coolant level, and the pressure build-up in the containment. In the Industrial Safety field it is helpful for estimating the leakage rate of toxic gases Tom liquefied gas pressure vessels, depressurization of pressure vessels, and explosion conditions due to liquefied gas release. For physical description of non-equilibrium two-phase critical flow it would be convenient to divide the flow into two stages. The first stage is the flow of subcooled liquid at constant temperature and uniform pressure drop (i.e., the case of incompressible fluid and uniform piping cross section). The rapid flow of the liquid causes a delay in the boiling of the liquid, which begins to boil below saturation pressure, at thermal non-equilibrium. The boiling is the beginning of the second stage, characterized by a sharp increase of the pressure drop. The liquid temperature on the second stage is almost constant because most of the energy for vaporization is supplied from the large pressure drop The present work will focus on the two-phase critical pressure of water, since water serves as coolant in the vast majority of nuclear power reactors throughout the world. (author).

Critical pressure of non-equilibrium two-phase critical flow

International Nuclear Information System (INIS)

Minzer, U.

1996-01-01

Critical pressure is defined as the pressure existing at the exit edge of the piping, when it remains constant despite a decrease in the back. According to this definition the critical pressure is larger than the back pressure and for two-phase conditions below saturation pressure. The two-phase critical pressure has a major influence on the two-phase critical flow characteristics. Therefore it is of High significance in calculations of critical mass flux and critical depressurization rate, which are important in the fields of Nuclear Reactor Safety and Industrial Safety. At the Nuclear Reactor Safety field is useful for estimations of the Reactor Cooling System depressurization, the core coolant level, and the pressure build-up in the containment. In the Industrial Safety field it is helpful for estimating the leakage rate of toxic gases Tom liquefied gas pressure vessels, depressurization of pressure vessels, and explosion conditions due to liquefied gas release. For physical description of non-equilibrium two-phase critical flow it would be convenient to divide the flow into two stages. The first stage is the flow of subcooled liquid at constant temperature and uniform pressure drop (i.e., the case of incompressible fluid and uniform piping cross section). The rapid flow of the liquid causes a delay in the boiling of the liquid, which begins to boil below saturation pressure, at thermal non-equilibrium. The boiling is the beginning of the second stage, characterized by a sharp increase of the pressure drop. The liquid temperature on the second stage is almost constant because most of the energy for vaporization is supplied from the large pressure drop The present work will focus on the two-phase critical pressure of water, since water serves as coolant in the vast majority of nuclear power reactors throughout the world. (author)

Mean-Field Critical Behavior and Ergodicity Break in a Nonequilibrium One-Dimensional Rsos Growth Model

Science.gov (United States)

Mendonça, J. Ricardo G.

We investigate the nonequilibrium roughening transition of a one-dimensional restricted solid-on-solid model by directly sampling the stationary probability density of a suitable order parameter as the surface adsorption rate varies. The shapes of the probability density histograms suggest a typical Ginzburg-Landau scenario for the phase transition of the model, and estimates of the "magnetic" exponent seem to confirm its mean-field critical behavior. We also found that the flipping times between the metastable phases of the model scale exponentially with the system size, signaling the breaking of ergodicity in the thermodynamic limit. Incidentally, we discovered that a closely related model not considered before also displays a phase transition with the same critical behavior as the original model. Our results support the usefulness of off-critical histogram techniques in the investigation of nonequilibrium phase transitions. We also briefly discuss in the appendix a good and simple pseudo-random number generator used in our simulations.

Quantum entanglement and criticality of the antiferromagnetic Heisenberg model in an external field

International Nuclear Information System (INIS)

Liu Guanghua; Li Ruoyan; Tian Guangshan

2012-01-01

By Lanczos exact diagonalization and the infinite time-evolving block decimation (iTEBD) technique, the two-site entanglement as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization in the antiferromagnetic Heisenberg (AFH) model under an external field are investigated. With increasing external field, the small size system shows some distinct upward magnetization stairsteps, accompanied synchronously with some downward two-site entanglement stairsteps. In the thermodynamic limit, the two-site entanglement, as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization are calculated, and the critical magnetic field h c = 2.0 is determined exactly. Our numerical results show that the quantum entanglement is sensitive to the subtle changing of the ground state, and can be used to describe the magnetization and quantum phase transition. Based on the discontinuous behavior of the first-order derivative of the entanglement entropy and fidelity per site, we think that the quantum phase transition in this model should belong to the second-order category. Furthermore, in the magnon existence region (h < 2.0), a logarithmically divergent behavior of block entanglement which can be described by a free bosonic field theory is observed, and the central charge c is determined to be 1. (paper)

Skeletal muscle oxygen pressure fields in artificially ventilated, critically ill patients

International Nuclear Information System (INIS)

Lund, N.; Jorfeldt, L.; Lewis, D.H.; Oedman, S.

1980-01-01

The MDO (Mehrdraht Dostmund Oberflaeche) oxygen electrode was used in a study of skeletal muscle oxygen pressure fields, presented as histograms, in critically ill patients artificially ventilated with gas mixtures of different oxygen concentrations. The histograms were compared with forearm blood flow measurements performed with strain gauge plethysmography. Local blood flow and permeability-surface area product (PS) were also studied by the simultaneous clearances of 133 xenon and 51 Cr-EDTA. The histogram distribution type was normal, i.e. approximately Gaussian, at arterial oxygen pressure levels between 10 and 18 kPa. At arterial oxygen pressures outside this range the histogram distribution types were abnormal, i.e. they showed a non-symmetrical distribution of oxygen pressure values, but their mean was approximately the same as in the normal histogram. However, there were significantly higher tissue oxygen pressure mean values in the patients (3.43 kPa) than in a group of healthy human volunteers (2.25 kPa). Mean forearm blood flow and the clearances of 133 xenon and 51 Cr-EDTA showed marked variations during the measurements both intraindividually and interindividually. Mean forearm blood flow and mean clearances of 133 xenon showed opposite trends compared with arterial oxygen pressures. Mean clearances of 51 Cr-EDTA and mean PS showed minor variations at the different arterial oxygen pressure levels. (author)

Method to increase the transition temperature and for the critical magnetic field strength of the known intermetallic compounds of vanadium or niobium

International Nuclear Information System (INIS)

Winter, H.

1977-01-01

The invention deals with a method to raise the transition temperature and critical magnetic field strength of superconducting, intermetallic compounds of vanadium and niobium. For example, a niobium alloy with 4 wt.% Al in melted in vacuum electric arc and formed into a sheet of about 1 mm thick. Strips of this sheet are electrically heated up to 1,900 0 C for one hour in a high-vacuum oven. The strips are then annealed in evacuated quartz ampoules for 120 hours at 800 0 C. These strips have a transition temperature of 24 K and a critical magnetic field strength of 600 kg; the critical current density was 5 x 10 4 A/cm 2 . (HPOE) [de

Hybridized Kibble-Zurek scaling in the driven critical dynamics across an overlapping critical region

Science.gov (United States)

Zhai, Liang-Jun; Wang, Huai-Yu; Yin, Shuai

2018-04-01

The conventional Kibble-Zurek scaling describes the scaling behavior in the driven dynamics across a single critical region. In this paper, we study the driven dynamics across an overlapping critical region, in which a critical region (Region A) is overlaid by another critical region (Region B). We develop a hybridized Kibble-Zurek scaling (HKZS) to characterize the scaling behavior in the driven process. According to the HKZS, the driven dynamics in the overlapping region can be described by the critical theories for both Region A and Region B simultaneously. This results in a constraint on the scaling function in the overlapping critical region. We take the quantum Ising chain in an imaginary longitudinal field as an example. In this model, the critical region of the Yang-Lee edge singularity and the critical region of the ferromagnetic-paramagnetic phase transition overlap with each other. We numerically confirm the HKZS by simulating the driven dynamics in this overlapping critical region. The HKZSs in other models are also discussed.

Reimagining Critical Theory

Science.gov (United States)

Rexhepi, Jevdet; Torres, Carlos Alberto

2011-01-01

This paper discusses Critical Theory, a model of theorizing in the field of the political sociology of education. We argue for a "reimagined" Critical Theory to herald an empowering, liberatory education that fosters curiosity and critical thinking, and a means for successful bottom-up, top-down political engagement. We present arguments…

Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems.

Science.gov (United States)

Ogawa, Shun; Yamaguchi, Yoshiyuki Y

2015-06-01

An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.

Local Magnetic Fields in Ferromagnetics Studied by Positive Muon Precession

CERN Multimedia

2002-01-01

Positive muons are used to study local magnetic fields in different materials. A polarized muon beam is employed with energies of 30-50 MeV, and the muons are stopped in the target being studied. During its lifetime the muon will precess in the magnetic fields present, and after the decay of the muon the emitted positron is detected in plastic scintillators. The time and angle of the detected positron is used to calculate the magnetic field at the position of the muon in the sample. \\\\ \\\\ The detector system consists of plastic scintillators. Most of the measurements are made in an applied magnetic field. A dilution cryostat is used to produce temperatures down to well below $ 1 ^0 $ K. \\\\ \\\\ The present line of experiments concern mainly: \\item a)~~~~Local magnetism in the paramagnetic state of the Lave's phase type REAl$_{2} $ and RENi$_{2} $ systems ~~~where RE is a rare-earth ion. \\item b)~~~~Local magnetic fields and critical behaviour of the magnetism in Gd metal. \\item c)~~~~Investigation of flux exclu...

Quantum Critical Higgs

Science.gov (United States)

Bellazzini, Brando; Csáki, Csaba; Hubisz, Jay; Lee, Seung J.; Serra, Javi; Terning, John

2016-10-01

The appearance of the light Higgs boson at the LHC is difficult to explain, particularly in light of naturalness arguments in quantum field theory. However, light scalars can appear in condensed matter systems when parameters (like the amount of doping) are tuned to a critical point. At zero temperature these quantum critical points are directly analogous to the finely tuned standard model. In this paper, we explore a class of models with a Higgs near a quantum critical point that exhibits non-mean-field behavior. We discuss the parametrization of the effects of a Higgs emerging from such a critical point in terms of form factors, and present two simple realistic scenarios based on either generalized free fields or a 5D dual in anti-de Sitter space. For both of these models, we consider the processes g g →Z Z and g g →h h , which can be used to gain information about the Higgs scaling dimension and IR transition scale from the experimental data.

Criticality and novel quantum liquid phases in Ginzburg-Landau theories with compact and non-compact gauge fields

Energy Technology Data Exchange (ETDEWEB)

Smiseth, Jo

2005-07-01

The critical properties of three-dimensional U(1)-symmetric lattice gauge theories have been studied. The models apply to various physical systems such as insulating phases of strongly correlated electron systems as well as superconducting and superfluid states of liquid metallic hydrogen under extreme pressures. The thesis contains an introductory part and a collection of research papers of which seven are published works and one is submitted for publication. The outline of this thesis is as follows. In Chapter 2 the theory of phase transitions is discussed with emphasis on continuous phase transitions, critical phenomena and phase transitions in gauge theories. In the next chapter the phases of the abelian Higgs model are presented, and the critical phenomena are discussed. Furthermore, the multicomponent Ginzburg-Landau theory and the applications to liquid metallic hydrogen are presented. Chapter 4 contains an overview of the Monte Carlo integration scheme, including the Metropolis algorithm, error estimates, and re weighting techniques. This chapter is followed by the papers I-VIII. Paper I: Criticality in the (2+1)-Dimensional Compact Higgs Model and Fractionalized Insulators. Paper II: Phase structure of (2+1)-dimensional compact lattice gauge theories and the transition from Mott insulator to fractionalized insulator. Paper III: Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials. Paper IV: Phase structure of Abelian Chern-Simons gauge theories. Paper V: Critical Properties of the N-Color London Model. Paper VI: Field- and temperature induced topological phase transitions in the three-dimensional N-component London superconductor. Paper VII: Vortex Sublattice Melting in a Two-Component Superconductor. Paper VIII: Observation of a metallic superfluid in a numerical experiment (ml)

Critical review of studies on atmospheric dispersion in coastal regions

International Nuclear Information System (INIS)

Shearer, D.L.; Kaleel, R.J.

1982-09-01

This study effort was required as a preliminary step prior to initiation of field measurements of atmospheric dispersion in coastal regions. The Nuclear Regulatory Commission (NRC) is in the process of planning an extensive field measurement program to generate data which will serve as improved data bases for licensing decisions, confirmation of regulations, standards, and guides, and for site characterizations. The study being reported here is an effort directed to obtaining as much information as is possible from existing studies that is relevant toward NRC's objectives. For this study, reports covering research and meteorological measurements conducted for industrial purposes, utility needs, military objectives, and academic studies were obtained and critically reviewed in light of NRC's current data needs. This report provides an interpretation of the extent of existing usable information, an indication of the potential for tailoring existing research toward current NRC information needs, and recommendations for several follow-on studies which could provide valuable additional information through reanalysis of the data. Recommendations are also offered regarding new measurement programs. Emphasis is placed on the identification and acquisition of data from atmospheric tracer studies conducted in coastal regions. A total of 225 references were identified which deal with the coastal atmosphere, including meteorological and tracer measurement programs, theoretical descriptions of the relevant processes, and dispersion models

Critical current density analysis of ex situ MgB2 wire by in-field and temperature Hall probe imaging

International Nuclear Information System (INIS)

Bartolome, E; Granados, X; Cambel, V; Fedor, J; Kovac, P; Husek, I

2005-01-01

The irreversible magnetic behaviour at different temperatures of an ex situ Fe-alloy/MgB 2 wire, exhibiting a granular compositional distribution, was studied using an in-field, high resolution Hall probe imaging system. Quantitative information about the local current density was obtained by solving the Biot-Savart inversion problem. The flux penetration and current distribution maps obtained can be attributed to a inhomogeneous compositional 'plum-cake-like' system, consisting of large, isolated MgB 2 agglomerations embedded in a matrix of finely distributed MgB 2 +MgO. The critical current densities within the grains and their evolution with the applied magnetic field and temperature have been obtained, and compared to the mean J c (H,T) in the matrix

Applications of Canonical transformations and nontrivial vacuum solutions to flavor mixing and critical phenomena in quantum field theory

International Nuclear Information System (INIS)

Mishchenko, Yuriy

2004-01-01

MISHCHENKO, YURIY. Applications of Canonical Transformations and Nontrivial Vacuum Solutions to flavor mixing and critical phenomena in Quantum Field Theory. (Under the direction of Chueng-Ryong Ji.) In this dissertation we consider two recent applications of Bogoliubov Transformation to the phenomenology of quantum mixing and the theory of critical phenomena. In recent years quantum mixing got in the focus of the searches for New Physics due to its unparalleled sensitivity to SM parameters and indications of neutrino mixing. It was recently suggested that Bogoliubov Transformation may be important in proper definition of the flavor states that otherwise results in problems in perturbative treatment. As first part of this dissertation we investigate this conjecture and develop a complete formulation of such a mixing field theory involving introduction of general formalism, analysis of space-time conversion and phenomenological implications. As second part of this dissertati

Applications of Canonical transformations and nontrivial vacuum solutions to flavor mixing and critical phenomena in quantum field theory

Energy Technology Data Exchange (ETDEWEB)

Mishchenko, Yuriy [North Carolina State Univ., Raleigh, NC (United States)

2004-12-01

MISHCHENKO, YURIY. Applications of Canonical Transformations and Nontrivial Vacuum Solutions to flavor mixing and critical phenomena in Quantum Field Theory. (Under the direction of Chueng-Ryong Ji.) In this dissertation we consider two recent applications of Bogoliubov Transformation to the phenomenology of quantum mixing and the theory of critical phenomena. In recent years quantum mixing got in the focus of the searches for New Physics due to its unparalleled sensitivity to SM parameters and indications of neutrino mixing. It was recently suggested that Bogoliubov Transformation may be important in proper definition of the flavor states that otherwise results in problems in perturbative treatment. As first part of this dissertation we investigate this conjecture and develop a complete formulation of such a mixing field theory involving introduction of general formalism, analysis of space-time conversion and phenomenological implications. As second part of this dissertati

Critical incidents among women entrepreneurs: Personal and professional issues

Directory of Open Access Journals (Sweden)

Vânia Maria Jorge Nassif

2016-06-01

Full Text Available ABSTRACT The objective of this paper is to analyze critical situations experienced by women entrepreneurs and understand how they have overcome such situations. The study contributes to the understanding of the issues related to the activities of women entrepreneurs and shows that the use of the critical incident technique is relevant to the development of research in the field of entrepreneurship. The data were collected using a specific form with 115 women participating in the study. The analysis of critical incidents showed that in addition to the practical issues regarding the management of their business, emotions are interconnected with their business development. Unlike international studies in the field, the critical incidents experienced by Brazilian women entrepreneurs overlap with personal aspects. The women involved in this study face emotional difficulties, but are also motivated by strong feelings of determination to overcome their problems.

Nuclear Criticality Technology and Safety Project parameter study database

International Nuclear Information System (INIS)

Toffer, H.; Erickson, D.G.; Samuel, T.J.; Pearson, J.S.

1993-03-01

A computerized, knowledge-screened, comprehensive database of the nuclear criticality safety documentation has been assembled as part of the Nuclear Criticality Technology and Safety (NCTS) Project. The database is focused on nuclear criticality parameter studies. The database has been computerized using dBASE III Plus and can be used on a personal computer or a workstation. More than 1300 documents have been reviewed by nuclear criticality specialists over the last 5 years to produce over 800 database entries. Nuclear criticality specialists will be able to access the database and retrieve information about topical parameter studies, authors, and chronology. The database places the accumulated knowledge in the nuclear criticality area over the last 50 years at the fingertips of a criticality analyst

Did Somebody Say Neoliberalism? On the Uses and Limitations of a Critical Concept in Media and Communication Studies

Directory of Open Access Journals (Sweden)

Christian Garland

2012-05-01

Full Text Available This paper explores the political-economic basis and ideological effects of talk about neoliberalism with respect to media and communication studies. In response to the supposed ascendancy of the neoliberal order since the 1980s, many media and communication scholars have redirected their critical attentions from capitalism to neoliberalism. This paper tries to clarify the significance of the relatively new emphasis on neoliberalism in the discourse of media and communication studies, with particular reference to the 2011 phone hacking scandal at The News of the World. Questioning whether the discursive substitution of ‘neoliberalism’ for ‘capitalism’ offers any advances in critical purchase or explanatory power to critics of capitalist society and its media, the paper proposes that critics substitute a Marxist class analysis in place of the neoliberalism-versus-democracy framework that currently dominates in the field.

Anomalous enhancement of the lower critical field deep in the superconducting state of LaRu4As12

Science.gov (United States)

Juraszek, J.; Bochenek, Ł.; Wawryk, R.; Henkie, Z.; Konczykowski, M.; Cichorek, T.

2018-05-01

LaRu4As12 with the critical temperature Tc = 10.4 K displays several features which point at a non-singlet superconducting order parameter, although the bcc crystal structure of the filled skutterudites does not favour the emergence of multiple energy gaps. LaRu4As12 displays an unexpected enhancement of the lower critical field deep in superconducting state which can be attributed to the existence of two superconducting gaps. At T = 0.4 K, the local magnetization measurements were performed utilizing miniaturized Hall sensors.

Numerical analysis of temperature field improvement with nanoparticles designed to achieve critical power dissipation in magnetic hyperthermia

Science.gov (United States)

Tang, Yundong; Flesch, Rodolfo C. C.; Jin, Tao

2017-07-01

Magnetic nanoparticle (MNP) hyperthermia is a promising emerging therapy for cancer treatment that is minimally invasive and has been successfully used to treat different types of tumors. The power dissipation of MNPs, which is one of the most important factors during a hyperthermia treatment, is determined by the properties of MNPs and characteristics of the magnetic field. This paper proposes a method based on the finite element analysis for determining the value of the power dissipation of particles (PDP) that can maximize the average temperature of the tumor during treatment and at the same time guarantee that the maximum temperature is within the therapeutic range. The application of the critical PDP value can improve the effectiveness of the treatment since it increases the average temperature in the tumor region while limiting the damage to the healthy tissue that surrounds it. After the critical PDP is determined for a specific model, it is shown how the properties of the MNPs can be chosen to achieve the desired PDP value. The transient behavior of the temperature distribution for two different models considering blood vessels is analyzed as a case study, showing that the presence of a blood vessel inside the tumor region can significantly decrease the uniformity of the temperature field and also increase the treatment duration given its cooling effects. To present a solution that does not depend upon a good model of the tumor region, an alternative method that uses MNPs with low Curie temperature is proposed, given the temperature self-regulating properties of such MNPs. The results demonstrate that the uniformity of the temperature field can be significantly increased by combining the optimization procedure proposed in this paper with the use of low-Curie-temperature MNPs.

Hubbard pair cluster in the external fields. Studies of the magnetic properties

Science.gov (United States)

Balcerzak, T.; Szałowski, K.

2018-06-01

The magnetic properties of the two-site Hubbard cluster (dimer or pair), embedded in the external electric and magnetic fields and treated as the open system, are studied by means of the exact diagonalization of the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The phase diagrams, on-site magnetizations, spin-spin correlations, mean occupation numbers and hopping energy are investigated and illustrated in figures. An influence of temperature, mean electron concentration, Coulomb U parameter and external fields on the quantities of interest is presented and discussed. In particular, the anomalous behaviour of the magnetization and correlation function vs. temperature near the critical magnetic field is found. Also, the effect of magnetization switching by the external fields is demonstrated.

Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

International Nuclear Information System (INIS)

Suzdalev, I.P.

2005-01-01

Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

Order parameter effect critical fields and current of Y1–xPrx:123 superconductors

Directory of Open Access Journals (Sweden)

Sedky A.

2018-03-01

Full Text Available Fluctuation induced conductivity by Pr substitution at Y sites of Y1-xPrx:123 superconductors is reported. It is found that the mean field temperature Tcmf, deduced from the peak of dρ/dT versus T plot, gradually decreases by increasing Pr up to 0.40. The order parameter dimensionality (OPD is estimated from the slope of the logarithmic plot between excess conductivity Δσ and reduced temperature є. Interestingly, the crossover from 2D to 3D is obtained for samples with Pr = 0.00, 0.10 and 0.20, while with increasing Pr up to 0.40, the crossover from 0D to quasi-2D is obtained. On the other hand, the calculated values of interlayer coupling, coherence lengths, critical fields and critical current decrease with increasing Pr up to 0.20, but with the further increase of Pr, up to 0.40, they increase. The hole carriers/Cu ions anisotropy and G-L parameter gradually increase with Pr up to 0.40. Our results are discussed in terms of the effects of Pr substitution at Y site, such as oxygen rearrangements, anisotropy, hybridization and localization of holes in the overdoped region.

Strategic Planning for Research in Pediatric Critical Care.

Science.gov (United States)

Tamburro, Robert F; Jenkins, Tammara L; Kochanek, Patrick M

2016-11-01

To summarize the scientific priorities and potential future research directions for pediatric critical care research discussed by a panel of experts at the inaugural Strategic Planning Conference of the Pediatric Trauma and Critical Illness Branch of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Expert opinion expressed during the Strategic Planning Conference. Not applicable. Chaired by an experienced expert from the field, issues relevant to the conduct of pediatric critical care research were discussed and debated by the invited participants. Common themes and suggested priorities were identified and coalesced. Of the many pathophysiologic conditions discussed, the multiple organ dysfunction syndrome emerged as a topic in need of more study that is most relevant to the field. Additionally, the experts offered that the interrelationship and impact of critical illness on child development and family functioning are important research priorities. Consequently, long-term outcomes research was encouraged. The expert group also suggested that multidisciplinary conferences are needed to help identify key knowledge gaps to advance and direct research in the field. The Pediatric Critical Care and Trauma Scientist Development National K12 Program and the Collaborative Pediatric Critical Care Research Network were recognized as successful and important programs supported by the branch. The development of core data resources including biorepositories with robust phenotypic data using common data elements was also suggested to foster data sharing among investigators and to enhance disease diagnosis and discovery. Multicenter clinical trials and innovative study designs to address understudied and poorly understood conditions were considered important for field advancement. Finally, the growth of the pediatric critical care research workforce was offered as a priority that could be spawned in many ways including by expanded

APS Quantum Critical Higgs

CERN Document Server

Bellazzini, Brando; Hubisz, Jay; Lee, Seung J.; Serra, Javi; Terning, John

2016-01-01

The appearance of the light Higgs boson at the LHC is difficult to explain, particularly in light of naturalness arguments in quantum field theory. However light scalars can appear in condensed matter systems when parameters (like the amount of doping) are tuned to a critical point. At zero temperature these quantum critical points are directly analogous to the finely tuned standard model. In this paper we explore a class of models with a Higgs near a quantum critical point that exhibits non-mean-field behavior. We discuss the parametrization of the effects of a Higgs emerging from such a critical point in terms of form factors, and present two simple realistic scenarios based on either generalized free fields or a 5D dual in AdS space. For both of these models we consider the processes $gg\\to ZZ$ and $gg\\to hh$, which can be used to gain information about the Higgs scaling dimension and IR transition scale from the experimental data.

This Isn't Business, It's Personal: Personal Narratives in the Field of Composition Studies

Science.gov (United States)

Golar, Norman

2010-01-01

I focus on three critical autobiographies in the field of composition studies: Mike Rose's "Lives on the Boundary: A Moving Account of the Struggles and Achievements of America's Educationally Underprepared," Keith Gilyard's "Voices of the Self: A Study of Language Competence," and Victor Villanueva, Jr.'s "Bootstraps: From an American Academic of…

Critical Thinking in Nurse Anesthesia Education: A Pilot Study

Science.gov (United States)

Burns, Shari; Mendel, Shaun; Fisher, Rodney; Cooper, Kimball; Fisher, Michael

2013-01-01

Critical thinking is pivotal for student success in health professions education. Knowing the critical thinking ability of the learner helps educators tailor curriculum to enhance critical thinking. A quantitative comparative pilot study assessed critical thinking ability for students at two distinct points in a nurse anesthesia program…

Critical Surveillance Studies in the Information Society

Directory of Open Access Journals (Sweden)

Thomas Allmer

2011-11-01

Full Text Available The overall aim of this paper is to clarify how we can theorize and systemize economic surveillance. Surveillance studies scholars like David Lyon stress that economic surveillance such as monitoring consumers or the workplace are central aspects of surveillance societies. The approach that is advanced in this work recognizes the importance of the role of the economy in contemporary surveillance societies. The paper at hand constructs theoretically founded typologies in order to systemize the existing literature of surveillance studies and to analyze examples of surveillance. Therefore, it mainly is a theoretical approach combined with illustrative examples. This contribution contains a systematic discussion of the state of the art of surveillance and clarifies how different notions treat economic aspects of surveillance. In this work it is argued that the existing literature is insufficient for studying economic surveillance. In contrast, a typology of surveillance in the modern economy, which is based on foundations of a political economy approach, allows providing a systematic analysis of economic surveillance on the basis of current developments on the Internet. Finally, some political recommendations are drawn in order to overcome economic surveillance. This contribution can be fruitful for scholars who want to undertake a systematic analysis of surveillance in the modern economy and who want to study the field of surveillance critically.

Criticality safety studies at VTT Energy

International Nuclear Information System (INIS)

Roine, T.; Anttila, M.

1995-01-01

At VTT Energy a compact reactor physics calculation system is applied in many kind of problems. Generation of group constants for static and dynamic core calculations, flux and dose rate calculations as well as criticality safety studies are performed basically with the same codes. In the presentation a short overview of the wide variety of criticality safety problems analyzed at VTT Energy is given. The calculation system with some illustrative examples is also described. (12 refs., 1 tab.)

The interface between clinicians and laboratory staff: A field study in northern Tanzania

Directory of Open Access Journals (Sweden)

Coosje J. Tuijn

2014-07-01

Conclusions: Hospital managers, clinicians and laboratory workers need to recognise the critical and complementary roles each professional plays and the importance of addressing the gap between them. Field application of the framework proved successful, justifying the expansion of this study to a larger geographical area to include additional healthcare institutions

The experience of critically ill children: A phenomenological study of discomfort and comfort.

Science.gov (United States)

Carnevale, Franco A; Gaudreault, Josée

2013-01-01

Emerging evidence indicates that critically ill children are particularly at risk for incurring significant psychological harm. Little is known about these children's actual experiences. The aim of the study was to examine children's experience of critical illness. The research question was: What are a critically ill child's sources of discomfort and comfort? Interpretive phenomenology was selected as the study's method. Children's accounts were examined to identify what they considered meaningful, in terms of their experienced discomfort and comfort. Data sources included formal and informal interviews with child-participants, drawings provided by some participants, and field-notes documenting observed non-verbal data. Twelve children were enrolled in the study, ranging from 3 to 17years of age; including four girls and eight boys. Although all participants were able to discuss the discomfort and comfort they experienced, they reported difficulties in remembering part or most of their experience. Some participants characterized their Pediatric Intensive Care Unit stay quite favourably or as "not that bad", while some described their experience unfavourably. Diverse types of discomforts were reported, including fears and worries, hurt and pain, invasive interventions, missing significant people, noise, food or eating problems, boredom, physical symptoms, as well as four additional discomforts reported by individual participants. Several sources of comfort were described, including parents, visitors and friends, hospital staff (principally nurses), stuffed animal/favourite blanket, entertainment and play, food, selected medical interventions, thinking of going home, being able to walk or run, sleep, waking up, gifts, along with two other comforts reported by individual participants. Embodiment and a tension between aloneness and being with were identified as the principal phenomena underlying these children's experiences. The findings complement existing knowledge

Results of 16 years' experiments at the critical facility of Valduc

International Nuclear Information System (INIS)

Houelle, M.; Mangin, D.; Maubert, L.

After briefly recalling the sub-critical approach procedure, the fields of experimental studies on criticality explored at the Valduc Criticality Station since 1963 are listed. This was the year in which the ''appareillage B'' went into service as the first installation of sub-critical experiments of the Section [fr

Criticality studies: One of the two pillars of criticality safety at the Belgonucleaire MOX plant

International Nuclear Information System (INIS)

Lance, B.; Maldague, T.; Evrard, G.; Renard, A.; Kockerols, P.

2001-01-01

The present paper focuses on the criticality studies performed by the Engineering Division of Belgonucleaire. These are one of the two pillars of the criticality prevention implemented for the Belgonucleaire MOX producing plant. (author)

Effects of Exponential Nonlinear Electrodynamics and External Magnetic Field on Holographic Superconductors

Science.gov (United States)

Sheykhi, A.; Abdollahzadeh, Z.

2018-03-01

We investigate the effects of an external magnetic field as well as exponential nonlinear electrodynamics on the properties of s-wave holographic superconductors. Our strategy for this study is the matching method, which is based on the match of the solutions near the horizon and on the boundary at some intermediate point. When the magnetic field is turned off, we obtain the critical temperature as well as the condensation operator and show that the critical exponent is still 1/2, which is the universal value in the mean field theory. Then, we turn on the magnetic field and obtain the critical magnetic field, B c , in order to study its behavior in terms of the temperature. Interestingly enough, we find that in the presence of exponential nonlinear electrodynamics, the critical temperature decreases, while the critical magnetic field increases compared to the Maxwell case. We also observe that the critical magnetic field increases with increasing the nonlinear parameter b.

A study of critical paths for feasibility studies of mining projects

International Nuclear Information System (INIS)

Sayadi, R.

2002-01-01

This work develops a model for design and realisation of profitability's and feasibility studies of a mining project. The model provides the structure of various necessary procedures to establish the feasibility studies and presents a logical system of task sequencing and information circulating between tasks. The specifications of mining projects, particularly their duration, complexity and high costs, necessitate design and realisation of feasibility study bases on the sufficient understanding of task behaviour and the critical path method view. For this purpose, critical paths with the highest frequency of occurrence were studied through several simulations. In addition, the critical tasks and sub tasks with the most probability were identified. The model introduced in this paper can serve as a perfect tool in feasibility study of a mining project. It can also be used as a basis of future development of mining software

Optimization study on the magnetic field of superconducting Halbach Array magnet

Science.gov (United States)

Shen, Boyang; Geng, Jianzhao; Li, Chao; Zhang, Xiuchang; Fu, Lin; Zhang, Heng; Ma, Jun; Coombs, T. A.

2017-07-01

This paper presents the optimization on the strength and homogeneity of magnetic field from superconducting Halbach Array magnet. Conventional Halbach Array uses a special arrangement of permanent magnets which can generate homogeneous magnetic field. Superconducting Halbach Array utilizes High Temperature Superconductor (HTS) to construct an electromagnet to work below its critical temperature, which performs equivalently to the permanent magnet based Halbach Array. The simulations of superconducting Halbach Array were carried out using H-formulation based on B-dependent critical current density and bulk approximation, with the FEM platform COMSOL Multiphysics. The optimization focused on the coils' location, as well as the geometry and numbers of coils on the premise of maintaining the total amount of superconductor. Results show Halbach Array configuration based superconducting magnet is able to generate the magnetic field with intensity over 1 Tesla and improved homogeneity using proper optimization methods. Mathematical relation of these optimization parameters with the intensity and homogeneity of magnetic field was developed.

Critical Pedagogy: EFL Teachers' Views, Experience and Academic Degrees

Science.gov (United States)

Mahmoodarabi, Mahsa; Khodabakhsh, Mohammad Reza

2015-01-01

Although critical pedagogy has brought about positive changes in the field of education by shifting from traditional pedagogy to emancipatory pedagogy, not much attention has been paid to the factors affecting teachers' beliefs of critical pedagogy and only few studies have been conducted to design reliable and valid instruments to study EFL…

Growth and decay of runaway electrons above the critical electric field under quiescent conditions

International Nuclear Information System (INIS)

Paz-Soldan, C.; Eidietis, N. W.; Wesley, J. C.; Granetz, R.; Hollmann, E. M.; Moyer, R. A.; Zhang, J.; Crocker, N. A.; Austin, M. E.; Wingen, A.; Zhu, Y.

2014-01-01

Extremely low density operation free of error field penetration supports the excitation of trace-level quiescent runaway electron (RE) populations during the flat-top of DIII-D Ohmic discharges. Operation in the quiescent regime allows accurate measurement of all key parameters important to RE excitation, including the internal broadband magnetic fluctuation level. RE onset is characterized and found to be consistent with primary (Dreicer) generation rates. Impurity-free collisional suppression of the RE population is investigated by stepping the late-time main-ion density, until RE decay is observed. The transition from growth to decay is found to occur 3–5 times above the theoretical critical electric field for avalanche growth and is thus indicative of anomalous RE loss. This suggests that suppression of tokamak RE avalanches can be achieved at lower density than previously expected, though extrapolation requires predictive understanding of the RE loss mechanism and magnitude

Criticality accident studies and methodology implemented at the CEA

International Nuclear Information System (INIS)

Barbry, Francis; Fouillaud, Patrick; Reverdy, Ludovic; Mijuin, Dominique

2003-01-01

Based on the studies and results of experimental programs performed since 1967 in the CRAC, then SILENE facilities, the CEA has devised a methodology for criticality accident studies. This methodology integrates all the main focuses of its approach, from criticality accident phenomenology to emergency planning and response, and thus includes aspects such as criticality alarm detector triggering, airborne releases, and irradiation risk assessment. (author)

Response to ``Comment on `Small field behavior of critical current in Y1Ba2Cu3O7 sintered samples' ''

Science.gov (United States)

Paternò, G.; Alvani, C.; Casadio, S.; Gambardella, U.; Maritato, L.

1989-05-01

In our response we would like to point out the fitting of the data has done to account for the shift of the maximum magnetic field dependence of the critical current. This shift on the order of 1 Gauss or less is gener ally observed in all our data and is attributable to the residual external field. Since we used a crude junction model, the self-field effects were not included. (AIP)

Study of HTS Wires at High Magnetic Fields

Energy Technology Data Exchange (ETDEWEB)

Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab

2009-01-01

Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

Correlation between in-field critical currents in Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes at 30 and 77 K

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V; Xu, A; Liu, Y; Khatri, ND; Lei, C; Chen, Y; Galstyan, E; Majkic, G

2014-03-11

Critical current (I-c) values of 1384 Lambda/12 mm, corresponding to a critical current density of 12.47 MA cm(-2) and a pinning force of 374 GN m(-3), have been achieved at 30 K, 3 T in the orientation of field parallel to the c axis (B parallel to c) in (Gd, Y)BaCuO tapes with 15 mol% Zr addition made by metal organic chemical vapor deposition (MOCVD). These tapes show pinning force levels as high as 453 GN m(-3) at 30 K. An analysis of the properties of 24-28 (Gd, Y)BaCuO tapes with 15 mol% Zr addition showed a lack of correlation between their critical currents at 30 K, 3 T (B parallel to c) and I-c values both at 77 K, zero field and at 77 K, 1 T (B parallel to c). However, a strong correlation was found between the critical currents at 30 K, 3 T and at 77 K, 3 T (B parallel to c). It has also been discovered that the minimum critical current (I-c, (min)) value at 77 K, 3 T has no influence on the I-c,I- (min) value at 30 K, 3 T, and it in turn depends on the ratio of the I-c values in the orientations of field parallel and perpendicular to the c axis at 77 K, 3 T.

Risk-Based, Hypothesis-Driven Framework for Hydrological Field Campaigns with Case Studies

Science.gov (United States)

Harken, B.; Rubin, Y.

2014-12-01

There are several stages in any hydrological modeling campaign, including: formulation and analysis of a priori information, data acquisition through field campaigns, inverse modeling, and prediction of some environmental performance metric (EPM). The EPM being predicted could be, for example, contaminant concentration or plume travel time. These predictions often have significant bearing on a decision that must be made. Examples include: how to allocate limited remediation resources between contaminated groundwater sites or where to place a waste repository site. Answering such questions depends on predictions of EPMs using forward models as well as levels of uncertainty related to these predictions. Uncertainty in EPM predictions stems from uncertainty in model parameters, which can be reduced by measurements taken in field campaigns. The costly nature of field measurements motivates a rational basis for determining a measurement strategy that is optimal with respect to the uncertainty in the EPM prediction. The tool of hypothesis testing allows this uncertainty to be quantified by computing the significance of the test resulting from a proposed field campaign. The significance of the test gives a rational basis for determining the optimality of a proposed field campaign. This hypothesis testing framework is demonstrated and discussed using various synthetic case studies. This study involves contaminated aquifers where a decision must be made based on prediction of when a contaminant will arrive at a specified location. The EPM, in this case contaminant travel time, is cast into the hypothesis testing framework. The null hypothesis states that the contaminant plume will arrive at the specified location before a critical amount of time passes, and the alternative hypothesis states that the plume will arrive after the critical time passes. The optimality of different field campaigns is assessed by computing the significance of the test resulting from each one

Big Data and Data Science in Critical Care.

Science.gov (United States)

Sanchez-Pinto, L Nelson; Luo, Yuan; Churpek, Matthew M

2018-05-09

The digitalization of the healthcare system has resulted in a deluge of clinical Big Data and has prompted the rapid growth of data science in medicine. Data science, which is the field of study dedicated to the principled extraction of knowledge from complex data, is particularly relevant in the critical care setting. The availability of large amounts of data in the intensive care unit, the need for better evidence-based care, and the complexity of critical illness makes the use of data science techniques and data-driven research particularly appealing to intensivists. Despite the increasing number of studies and publications in the field, so far there have been few examples of data science projects that have resulted in successful implementations of data-driven systems in the intensive care unit. However, given the expected growth in the field, intensivists should be familiar with the opportunities and challenges of Big Data and data science. In this paper, we review the definitions, types of algorithms, applications, challenges, and future of Big Data and data science in critical care. Copyright © 2018. Published by Elsevier Inc.

The effects of critical thinking instruction on training complex decision making

NARCIS (Netherlands)

Helsdingen, A.S.; Bosch, K. van den; Gog, T. van; Merriënboer, J.J.G. van

2010-01-01

Objective : Two field studies assessed the effects of critical thinking instruction on training and transfer of a complex decision-making skill. Background : Critical thinking instruction is based on studies of how experienced decision makers approach complex problems. Method : Participants

The Lathrop Wells volcanic center: Status of field and geochronology studies

International Nuclear Information System (INIS)

Crowe, B.; Morley, R.; Wells, S.; Geissman, J.; McDonald, E.; McFadden, L.; Perry, F.; Murrell, M.; Poths, J.; Forman, S.

1992-01-01

The purpose of this paper is to describe the status of field and geochronology studies of the Lathrop Wells volcanic center. Our perspective is that it is critical to assess all possible methods for obtaining cross-checking data to resolve chronology and field problems. It is equally important to consider application of the range of chronology methods available in Quaternary geologic research. Such an approach seeks to increase the confidence in data interpretations through obtaining convergence among separate isotopic, radiogenic, and age-correlated methods. Finally, the assumptions, strengths, and weaknesses of each dating method need to be carefully described to facilitate an impartial evaluation of results. The paper is divided into two parts. The first part describes the status of continuing field studies for the volcanic center for this area south of Yucca Mountain, Nevada. The second part presents an overview of the preliminary results of ongoing chronology studies and their constraints on the age and stratigraphy of the Lathrop Wells volcanic center. Along with the chronology data, the assumptions, strengths, and limitations of each methods are discussed

Critical temperature gradient and critical current density in thin films of a type I superconductor

Energy Technology Data Exchange (ETDEWEB)

Heubener, R P

1968-12-16

Measurements of the critical temperature gradient and the critical current density in superconducting lead films in a transverse magnetic field indicate that the critical current flows predominantly along the surface of the films and that the critical surface currents contribute only very little to the Lorentz force on a fluxoid.

Attractive forces study in macromolecules and critical systems; Etude des forces attractives dans les macromolecules et les systemes critiques

Energy Technology Data Exchange (ETDEWEB)

Penninckx-Sans, A.

1995-07-10

The attractive forces effect is particularly interesting at the proximity of a critical point. In a liquid system, there are two kinds of attractive forces in presence : the forces bound to the solution volume and those generated by the presence of the solution surface or by a solution interface. In the first case, the attractive forces are the more important as the system is in a critical field. For this study, the selected example is a polymer solution in a two solvents mixture. A formulation in terms of way integrals as part of statistical physics has lead us to find again some known results on the polymer chain conformation in the presence of two solvents (collapse of the polymer on itself) far from the critical point and to extend these results to the critical field. In the case of attractive forces created by the surface in some critical systems (polymer of infinite size in solution and binary mixture near the de mixture point), the adsorption profile created by the attraction of one specie by the surface, follows a scale law. The optical methods usually used for the study of these systems do not give characteristic sign of concentration profile in power law. In the case where the interaction potential between radiation and matter is attractive, the reflectivity gives a separate mark of the existence of the scale law in the form of a resonance. After some theoretical forecasts, the author has used this method on the binary mixture methanol-cyclohexane in order to reveal experimentally a reflectivity pseudo-discontinuity and then the existence of the power law in the critical adsorption profile. (O.L.). 69 refs., 60 tabs.

Transition from columnar to point pinning in coated conductors: critical currents that are independent of magnetic field direction

International Nuclear Information System (INIS)

Zuev, Yuri L; Hun Wee, Sung; Christen, David K

2012-01-01

We identify a sharp crossover in the vortex pinning of a high-temperature superconductor with nanocolumnar stacks of precipitates as strong vortex pinning centers. Above a particular, temperature-dependent field B X (T) the vortex response is no longer determined by the nanocolumns, and is instead determined by point-like pinning. This crossover is evident as a change in the dependence of the critical current density on the angle between the applied magnetic field and the nanocolumns. It also leads to the field-orientation-independent power law index n of the E–J curves. Below the transition, there is a strong maximum in J C when the field is aligned parallel to the columns and n depends on field direction. Above the transition, n is independent of the field direction and there is a J C minimum for H parallel to the columns. We discuss a possible mechanism for such behavior change, as well as testing and confirming a prediction that the crossover must become very broad at high temperatures and low fields. (paper)

A RE-INTRODUCTION TO ANOMALIES OF CRITICALITY

International Nuclear Information System (INIS)

Puigh, R.J.

2009-01-01

In 1974, a small innocuous document was submitted to the American Nuclear Society's Criticality Safety Division for publication that would have lasting impacts on this nuclear field The author was Duane Clayton, manager of the Battelle Pacific Northwest National Laboratory's Critical Mass Lab, the world's preeminent reactor critical experimenter with plutonium solutions. The document was entitled, 'Anomalies of Criticality'. 'Anomalies...' was a compilation of more than thirty separate and distinct examples of departures from what might be commonly expected in the field of nuclear criticality. Mr. Clayton's publication was the derivative of more than ten thousand experiments and countless analytical studies conducted world-wide on every conceivable reactor system imaginable: from fissile bearing solutions to solids, blocks to arrays of fuel rods, low-enriched uranium oxide systems to pure plutonium and highly enriched uranium systems. After publication, the document was commonly used within the nuclear fuel cycle and reactor community to train potential criticality/reactor analysts, experimenters and fuel handlers on important things for consideration when designing systems with critically 'safe' parameters in mind The purpose of this paper is to re-introduce 'Anomalies of Criticality' to the current Criticality Safety community and to add new 'anomalies' to the existing compendium. By so doing, it is the authors' hope that a new generation of nuclear workers and criticality engineers will benefit from its content and might continue to build upon this work in support of the nuclear renaissance that is about to occur

Assessment of critical thinking: a Delphi study.

Science.gov (United States)

Paul, Sheila A

2014-11-01

Nurse educators are responsible for preparing nurses who critically analyze patient information and provide meaningful interventions in today's complex health care system. By using the Delphi research method, this study, utilized the specialized and experiential knowledge of Certified Nurse Educators. This original Delphi research study asked Certified Nurse Educators how to assess the critical-thinking ability of nursing students in the clinical setting. The results showed that nurse educators need time, during the clinical experience, to accurately assess each individual nursing student. This study demonstrated the need for extended student clinical time, and a variety of clinical learning assessment tools. Copyright © 2014 Elsevier Ltd. All rights reserved.

Application of the string method to the study of critical nuclei in capillary condensation.

Science.gov (United States)

Qiu, Chunyin; Qian, Tiezheng; Ren, Weiqing

2008-10-21

We adopt a continuum description for liquid-vapor phase transition in the framework of mean-field theory and use the string method to numerically investigate the critical nuclei for capillary condensation in a slit pore. This numerical approach allows us to determine the critical nuclei corresponding to saddle points of the grand potential function in which the chemical potential is given in the beginning. The string method locates the minimal energy path (MEP), which is the most probable transition pathway connecting two metastable/stable states in configuration space. From the MEP, the saddle point is determined and the corresponding energy barrier also obtained (for grand potential). Moreover, the MEP shows how the new phase (liquid) grows out of the old phase (vapor) along the most probable transition pathway, from the birth of a critical nucleus to its consequent expansion. Our calculations run from partial wetting to complete wetting with a variable strength of attractive wall potential. In the latter case, the string method presents a unified way for computing the critical nuclei, from film formation at solid surface to bulk condensation via liquid bridge. The present application of the string method to the numerical study of capillary condensation shows the great power of this method in evaluating the critical nuclei in various liquid-vapor phase transitions.

Field and temperature scaling of the critical current density in commercial REBCO coated conductors

CERN Document Server

Senatore, Carmine; Bonura, Marco; Kulich, Miloslav; Mondonico, Giorgio

2016-01-01

Scaling relations describing the electromagnetic behaviour of coated conductors (CCs) greatly simplify the design of REBCO-based devices. The performance of REBCO CCs is strongly influenced by fabrication route, conductor architecture and materials, and these parameters vary from one manufacturer to the others. In the present work we have examined the critical surface for the current density, Jc(T,B,θ ), of coated conductors from six different manufacturers: American Superconductor Co. (US), Bruker HTS GmbH (Germany), Fujikura Ltd. (Japan), SuNAM Co. Ltd. (Korea), SuperOx ZAO (Russia) and SuperPower Inc. (US). Electrical transport and magnetic measurements were performed at temperatures between 4.2 K and 77 K and in magnetic field up to 19 T. Experiments were conducted at three different orientations of the field with respect to the crystallographic c-axis of the REBCO layer, θ = 0deg , 45deg and 90deg , in order to probe the angular anisotropy of Jc. In spite of the large variability of CCs performance, ...

Critical Thinking and Online Supplemental Instruction: A Case Study

Science.gov (United States)

Shaw, Cassandra S.; Holmes, Karen E.

2014-01-01

A wealth of research is available regarding supplemental instruction; however, a dearth exists regarding online supplemental instruction and critical thinking. This case study explored what was assumed to be known of critical thinking and investigated the extent to which critical thought was promoted within a university's online supplemental…

Using Bourdieu in Critical Mediatization Research: Communicational Doxa and Osmotic Pressures in the Field of UN Organizations

Directory of Open Access Journals (Sweden)

André Jansson

2015-05-01

Full Text Available This article develops a Bourdieusian approach to mediatization. It is argued that the Bourdieusian theories of doxa and fields can make valuable contributions to a critical perspective on mediatization, one that moves beyond the divides between institutionalist, social-constructivist and materialist understandings (e.g., Bourdieu, 1972/1977. Mediatization is here seen as the historically growing dependence on media technologies and institutions within diverse social fields and settings. In order to establish the link between mediatization and Bourdieu’s theories (ibid., the article introduces the concept of communicational doxa, which refers to the taken for granted communicational conventions and demands that regulate the inclusion of membership within a particular field. The article also shows how communicational doxa can be applied as an analytical concept. Findings from qualitative fieldwork carried out among highly mobile and skilled professionals within the field of UN organizations in Geneva, show how the autonomy of social agents is negotiated in relation to an increasingly mediatized communicational doxa.

Crack problem in superconducting cylinder with exponential distribution of critical-current density

Science.gov (United States)

Zhao, Yufeng; Xu, Chi; Shi, Liang

2018-04-01

The general problem of a center crack in a long cylindrical superconductor with inhomogeneous critical-current distribution is studied based on the extended Bean model for zero-field cooling (ZFC) and field cooling (FC) magnetization processes, in which the inhomogeneous parameter η is introduced for characterizing the critical-current density distribution in inhomogeneous superconductor. The effect of the inhomogeneous parameter η on both the magnetic field distribution and the variations of the normalized stress intensity factors is also obtained based on the plane strain approach and J-integral theory. The numerical results indicate that the exponential distribution of critical-current density will lead a larger trapped field inside the inhomogeneous superconductor and cause the center of the cylinder to fracture more easily. In addition, it is worth pointing out that the nonlinear field distribution is unique to the Bean model by comparing the curve shapes of the magnetization loop with homogeneous and inhomogeneous critical-current distribution.

The capabilities and scope-of-practice requirements of advanced life support practitioners undertaking critical care transfers: A Delphi study

Directory of Open Access Journals (Sweden)

Monique Venter

2016-11-01

Full Text Available Background. Critical care transfers (CCT refer to the high level of care given during transport (via ambulance, helicopter or fixed-wing aircraft of patients who are of high acuity. In South Africa (SA, advanced life support (ALS paramedics undertake CCTs. The scope of ALS in SA has no extended protocol regarding procedures or medications in terms of dealing with these CCTs. Aim. The aim of this study was to obtain the opinions of several experts in fields pertaining to critical care and transport and to gain consensus on the skills and scope-of-practice requirements of paramedics undertaking CCTs in the SA setting. Methods. A modified Delphi study consisting of three rounds was undertaken using an online survey platform. A heterogeneous sample (n=7, consisting of specialists in the fields of anaesthesiology, emergency medicine, internal medicine, critical care, critical care transport and paediatrics, was asked to indicate whether, in their opinion, selected procedures and medications were needed within the scope of practice of paramedics undertaking CCTs. Results. After three rounds, consensus was obtained in 70% (57/81 of procedures and medications. Many of these items are not currently within the scope of paramedics’ training. The panel felt that paramedics undertaking these transfers should have additional postgraduate training that is specific to critical care. Conclusion. Major discrepancies exist between the current scope of paramedic practice and the suggested required scope of practice for CCTs. An extended scope of practice and additional training should be considered for these practitioners.

Dynamical Mean Field Approximation Applied to Quantum Field Theory

CERN Document Server

Akerlund, Oscar; Georges, Antoine; Werner, Philipp

2013-12-04

We apply the Dynamical Mean Field (DMFT) approximation to the real, scalar phi^4 quantum field theory. By comparing to lattice Monte Carlo calculations, perturbation theory and standard mean field theory, we test the quality of the approximation in two, three, four and five dimensions. The quantities considered in these tests are the critical coupling for the transition to the ordered phase and the associated critical exponents nu and beta. We also map out the phase diagram in four dimensions. In two and three dimensions, DMFT incorrectly predicts a first order phase transition for all bare quartic couplings, which is problematic, because the second order nature of the phase transition of lattice phi^4-theory is crucial for taking the continuum limit. Nevertheless, by extrapolating the behaviour away from the phase transition, one can obtain critical couplings and critical exponents. They differ from those of mean field theory and are much closer to the correct values. In four dimensions the transition is sec...

Critical Thinking and EFL Learners' Performance on Different Writing Modes

Science.gov (United States)

Golpour, Farhad

2014-01-01

The essential function of critical thinking in education is obvious by many studies done in this field. The main purpose of this article is to find the relationship between critical thinking levels of Iranian EFL learners and their performance on different modes of writing. The sample of the study selected among those who studying English at the…

Critique and Contribute: A Practice-Based Framework for Improving Critical Data Studies and Data Science.

Science.gov (United States)

Neff, Gina; Tanweer, Anissa; Fiore-Gartland, Brittany; Osburn, Laura

2017-06-01

What would data science look like if its key critics were engaged to help improve it, and how might critiques of data science improve with an approach that considers the day-to-day practices of data science? This article argues for scholars to bridge the conversations that seek to critique data science and those that seek to advance data science practice to identify and create the social and organizational arrangements necessary for a more ethical data science. We summarize four critiques that are commonly made in critical data studies: data are inherently interpretive, data are inextricable from context, data are mediated through the sociomaterial arrangements that produce them, and data serve as a medium for the negotiation and communication of values. We present qualitative research with academic data scientists, "data for good" projects, and specialized cross-disciplinary engineering teams to show evidence of these critiques in the day-to-day experience of data scientists as they acknowledge and grapple with the complexities of their work. Using ethnographic vignettes from two large multiresearcher field sites, we develop a set of concepts for analyzing and advancing the practice of data science and improving critical data studies, including (1) communication is central to the data science endeavor; (2) making sense of data is a collective process; (3) data are starting, not end points, and (4) data are sets of stories. We conclude with two calls to action for researchers and practitioners in data science and critical data studies alike. First, creating opportunities for bringing social scientific and humanistic expertise into data science practice simultaneously will advance both data science and critical data studies. Second, practitioners should leverage the insights from critical data studies to build new kinds of organizational arrangements, which we argue will help advance a more ethical data science. Engaging the insights of critical data studies will

Magnetic-field induced Bose-Einstein condensation of magnons and critical behavior in interacting spin dimer system TlCuCl3

International Nuclear Information System (INIS)

Yamada, F.; Ono, T.; Tanaka, H.; Misguich, G.; Oshikawa, M.; Sakakibara, T.

2008-01-01

Magnetization measurements were performed to investigate the critical behavior of the field-induced magnetic ordering in gapped spin system TlCuCl 3 . The critical density of the magnons was obtained as a function of temperature and the magnon-magnon interaction constant was evaluated. The experimental phase boundary for T ≤ 5 K agrees almost perfectly with the magnon Bose-Einstein condensation (BEC) theory based on the Hartree-Fock approximation with realistic dispersion relations. The phase boundary can be described by the power law [H N (T)-H c ] ∝ T φ . With decreasing fitting temperature range, the critical exponent φ decreases and converges at φ(BEC) = 3/2 predicted by the magnon BEC theory. (authors)

Experimental study of low-titre critical two-phase flows

International Nuclear Information System (INIS)

Seynhaeve, Jean-Marie

1980-02-01

This report for engineering graduation addresses the analysis of two-phase critical flows obtained by expansion of a saturated or under-cooled liquid. For a titre greater than 0,1, theoretical studies give a rather good prediction of critical flow rates, whereas in the case of a lower titre, results obtained by published studies display some discrepancies, and the test duct geometry and important unbalances between phases seem to be at the origin of these discrepancies. In order to study these origins of discrepancies, three test campaigns have been performed: on a test duct provided by the CENG, on two long tubes, and on holes. Thus, after a bibliographical study which outlines drawbacks of previous studies, the author proposes a detailed description of experimental installations (creation of critical flows, measurement chain, measurement processing, measurement device calibration, quality and precision). Experimental results are then systematically explored, and differences are explained. The author then addresses the theoretical aspect of the determination of critical flow rates by reviewing calculation models and by comparing their results with experimental results. The validity of each model is thus discussed. The author then proposes a calculation model which can be applied to critical flows developed in holes. This model is notably inspired by experimental conclusions and gives very satisfying practical results

Criticality safety engineer training at WSRC

International Nuclear Information System (INIS)

Williamson, T.G.; Mincey, J.F.

1993-01-01

Two programs designed to prepare engineers for certification as criticality safety engineers are offered at Westinghouse Savannah River Company (WSRC). One program, Student On Loan Criticality Engineer Training (SOLCET), is an intensive 2-yr course involving lectures, rigorous problem assignments, and mentoring. The other program, In-Field Criticality Engineer Training (IN-FIELD), is a less intensive series of lectures and problem assignments. Both courses are conducted by members of the Applied Physics Group (APG) of the Savannah River Technical Center, the organization at WSRC responsible for the operation and maintenance of criticality codes and for training of code users

Critical data studies: An introduction

Directory of Open Access Journals (Sweden)

Andrew Iliadis

2016-10-01

Full Text Available Critical Data Studies (CDS explore the unique cultural, ethical, and critical challenges posed by Big Data. Rather than treat Big Data as only scientifically empirical and therefore largely neutral phenomena, CDS advocates the view that Big Data should be seen as always-already constituted within wider data assemblages. Assemblages is a concept that helps capture the multitude of ways that already-composed data structures inflect and interact with society, its organization and functioning, and the resulting impact on individuals’ daily lives. CDS questions the many assumptions about Big Data that permeate contemporary literature on information and society by locating instances where Big Data may be naively taken to denote objective and transparent informational entities. In this introduction to the Big Data & Society CDS special theme, we briefly describe CDS work, its orientations, and principles.

Effects of surface modification on the critical behaviour in multiple-surface-layer ferroelectric thin films

International Nuclear Information System (INIS)

Lu, Z X

2013-01-01

Using the usual mean-field theory approximation, the critical behaviour (i.e. the Curie temperature T c and the critical surface transverse field Ω sc ) in a multiple-surface-layer ferroelectric thin film is studied on the basis of the spin- 1/2 transverse Ising model. The dependence of the Curie temperature T c on the surface transverse field Ω s and the surface layer number N s are discussed in detail. Meanwhile the dependence of the critical surface transverse field Ω sc on the surface layer number N s is also examined. The numerical results indicate that the critical behaviour of ferroelectric thin films is obviously affected by modifications of the surface transverse field Ω s and surface layer number N s .

Choice of sample size for high transport critical current density in a granular superconductor: percolation versus self-field effects

International Nuclear Information System (INIS)

Mulet, R.; Diaz, O.; Altshuler, E.

1997-01-01

The percolative character of the current paths and the self-field effects were considered to estimate optimal sample dimensions for the transport current of a granular superconductor by means of a Monte Carlo algorithm and critical-state model calculations. We showed that, under certain conditions, self-field effects are negligible and the J c dependence on sample dimensions is determined by the percolative character of the current. Optimal dimensions are demonstrated to be a function of the fraction of superconducting phase in the sample. (author)

Reflections on Critical Thinking: Lessons from a Quasi-Experimental Study

Science.gov (United States)

Grussendorf, Jeannie; Rogol, Natalie C.

2018-01-01

In a pre/post quasi-experimental study assessing the impact of a specific curriculum on critical thinking, the authors employed a critical thinking curriculum in two sections of a U.S. foreign policy class. The authors found that the interactive and scaffolded critical thinking curriculum yielded statistically significant critical thinking…

A Critical Analysis of IQ Studies of Adopted Children

Science.gov (United States)

Richardson, Ken; Norgate, Sarah H.

2006-01-01

The pattern of parent-child correlations in adoption studies has long been interpreted to suggest substantial additive genetic variance underlying variance in IQ. The studies have frequently been criticized on methodological grounds, but those criticisms have not reflected recent perspectives in genetics and developmental theory. Here we apply…

Conflict, Education and the Global South: New Critical Directions

Science.gov (United States)

Novelli, Mario; Lopes Cardozo, Mieke T. A.

2008-01-01

This paper seeks to provide a starting point for a broader discussion on the development of a critical research agenda in the field of "Education and Conflict Studies." We begin the paper with a brief overview of the field of Education and Conflict drawing on a series of recent "overviews" of the field and locate this within…

Magnetic fields in laser heated plasmas

International Nuclear Information System (INIS)

Amiranoff, F.; Brackbill, J.; Colombant, D.; Grandjouan, N.

1984-01-01

With a fixed-ion code for the study of self-generated magentic fields in laser heated plasmas, the inhibition of thermal transport and the effect of the Nernst term are modeled for a KrF laser. For various values of the flux limiter, the response of a foil to a focused laser is calculated without a magnetic field and compared with the response calculated with a magnetic field. The results are: The Nernst term convects the magnetic field to densities above critical as found by Nishiguchi et al. (1984), but the field does not strongly inhibit transport into the foil. The field is also transported to sub-critical densities, where it inhibits thermal diffusion and enhance lateral transport by convection

Simulation of Field Dependence of Critical Current Densities of Bulk High Tc Superconducting Materials regarding Thermally Activated Flux Motion

Science.gov (United States)

Santosh, M.; Naik, S. Pavan Kumar; Koblischka, M. R.

2017-07-01

In the upcoming generation, bulk high temperature superconductors (HTS) will play a crucial and a promising role in numerous industrial applications ranging from Maglev trains to magnetic resonance imaging, etc. Especially, the bulk HTS as permanent magnets are suitable due to the fact that they can trap magnetic fields being several orders of magnitude higher than those of the best hard ferromagnets. The bulk HTS LREBa2Cu3O7-δ (LREBCO or LRE-123, LRE: Y, Gd, etc.,) materials could obtain very powerful compact superconducting super-magnets, which can be operated at the cheaper liquid nitrogen temperature or below due to higher critical temperatures (i.e., ∼90 K). As a result, the new advanced technology can be utilized in a more attractive manner for a variety of technological and medical applications which have the capacity to revolutionize the field. An understanding of the magnetic field dependence of the critical current density (J c(H)) is important to develop better adapted materials. To achieve this goal, a variety of Jc (H) behaviours of bulk LREBCO samples were modelled regarding thermally activated flux motion. In essence, the Jc (H) curves follows a certain criterion where an exponential model is applied. However, to fit the complete Jc (H) curve of the LRE-123 samples an unique model is necessary to explain the behavior at low and high fields. The modelling of the various superconducting materials could be understood in terms of the pinning mechanisms.

Critical Discourse Analysis in Literacy Education: A Review of the Literature

Science.gov (United States)

Rogers, Rebecca; Schaenen, Inda

2014-01-01

This article is a critical, integrative literature review of scholarship in literacy studies from 2004 to 2012 that draws on critical discourse analysis (CDA). We discuss key issues, trends, and criticisms in the field. Our methodology was carried out in three stages. First, we searched educational databases to locate literacy-focused CDA…

Wilson's theory of critical phenomena. Higher order corrections to critical exponents

International Nuclear Information System (INIS)

Zinn-Justin, J.

1973-01-01

The Wilson's theory of critical phenomena is presented, in the context of renormalized field theory in d dimension and of the Callan-Symanzik equations. This theory allows in particular to compute critical exponents that govern the behavior of some correlation functions near the critical temperature, as power series in epsilon=4-d, using the standard perturbation theory. Owing to the large value of the expansion parameter epsilon, whose physical value is one, it is very important to perform higher order calculations [fr

Reading the World's Classics Critically: A Keyword-Based Approach to Literary Analysis in Foreign Language Studies

Science.gov (United States)

García, Nuria Alonso; Caplan, Alison

2014-01-01

While there are a number of important critical pedagogies being proposed in the field of foreign language study, more attention should be given to providing concrete examples of how to apply these ideas in the classroom. This article offers a new approach to the textual analysis of literary classics through the keyword-based methodology originally…

Irreversible mean-field model of the critical behavior of charge-density waves below the threshold for sliding

Science.gov (United States)

Sornette, Didier

1993-05-01

A mean-field (MF) model of the critical behavior of charge-density waves below the threshold for sliding is proposed, which replaces the combined effect of the pinning force and of the forces exerted by the neighbors on a given particle n by an effective force threshold Xn. It allows one to rationalize the numerical results of Middleton and Fisher [Phys. Rev. Lett. 66 (1991) 92] on the divergence of the polarization and of the largest correlation length and of Pla and Nori [Phys. Rev. Lett. 67 (1991) 919] on the distribution D( d) of sliding bursts of size d, measured in narrow intervals of driving fields E at a finite distance below the threshold Ec.

Critical Kondo destruction and the violation of the quantum-to-classical mapping of quantum criticality

International Nuclear Information System (INIS)

Kirchner, Stefan; Si Qimiao

2009-01-01

Antiferromagnetic heavy fermion metals close to their quantum critical points display a richness in their physical properties unanticipated by the traditional approach to quantum criticality, which describes the critical properties solely in terms of fluctuations of the order parameter. This has led to the question as to how the Kondo effect gets destroyed as the system undergoes a phase change. In one approach to the problem, Kondo lattice systems are studied through a self-consistent Bose-Fermi Kondo model within the extended dynamical mean field theory. The quantum phase transition of the Kondo lattice is thus mapped onto that of a sub-Ohmic Bose-Fermi Kondo model. In the present article we address some aspects of the failure of the standard order-parameter functional for the Kondo-destroying quantum critical point of the Bose-Fermi Kondo model.

Critical points in magnetic systems

International Nuclear Information System (INIS)

Bongaarts, A.L.M.

1975-01-01

The magnetical phase transitions of CsCoCl 3 .2H 2 O and CsCoCl 3 .2D 2 O are investigated by neutron diffraction techniques with special attention to the critical points in the phase diagrams. CsCoCl 3 .2H 2 O turned out to be a one-dimentional magnetic antiferromagnet with ferromagnetic and antiferromagnetic interactions. In the vicinity of the Neel point, the critical behavior in zero magnetic field could be described as a three-dimentional long range ordering, while the fluctuations in the system are one-dimensional. In the presence of a magnetic field, the behavior of the system in the critical region of the magnetic phase diagram between the Neel temperature at zero field (3.3degK) and 1.85degK, was in good agreement with the theory. Below 1.85degK, the phase transition in a magnetic field changes into a line of triple points whose end point could be identified as a tricritical point, i.e., an intersection of three critical lines. The parameters derived from observations in the neighborhood of this tricritical point obey the scaling laws but are not in numerical agreement with theoretical predictions

Transportation of fissile materials and the danger of criticity

International Nuclear Information System (INIS)

Haon, D.; Leclerc, J.; Maubert, L.

1981-01-01

The authors examine the risk of criticity that can arise during the transportation of fissile matter. They then outline the regulations and studies made in the field of criticity-safety and the computation methods used. They discuss the applications that are reflected in the concept and design of fissile material packagings [fr

Influence of n,γ-field fluctuations on critical hydrogen concentration in the reactor primary coolant

International Nuclear Information System (INIS)

Arkhipov, O.; Kabakchi, S.

2014-01-01

One of the problems arising in operation of the NPP with reactors VVER/PWR are the consequences of the primary coolant radiolysis, namely, generation of the oxidizing particles intensifying the equipment corrosion rate. During operation of the reactor a decrease in concentration of oxidizing radiolysis products is provided with introduction of molecular hydrogen into the coolant. In this connection, the reliable estimation of Critical Hydrogen Concentration (CHC), sufficient for suppression of formation of oxidizing radiolysis products under specific in-pile conditions (reactor radiation dose rate, temperature, coolant chemical composition) is of practical interest. Unfortunately, the experimental data on CHC in-pile determination differ essentially from the values calculated. Critical hydrogen concentration is in the region of kinetic instability of radiation-chemical system. A slight change in hydrogen concentration leads to a sharp (by several orders) change in concentration of both short-lived (OH, HO 2 ) and stable (O 2 , H 2 O 2 ) oxidizing particles. In essence, when reaching the CHC, the radiation-chemical system changes over from one stable state to another. The paper deals with the results of the computer simulation of influence of short-term n,γ- field fluctuations on changing of the radiation-chemical system from the state with low concentration of oxidizing particles over to the state with their high concentrations. It is demonstrated that for the correct calculation of CHC in the primary coolant of VVER/PWR the non-uniformity of n,γ-field in the core shall be taken into account. (author)

Rationing critical care medicine: recent studies and current trends.

Science.gov (United States)

Ward, Nicholas S

2005-12-01

This paper reviews the literature on the rationing of critical care resources. Although much has been written about the concept of rationing, there have been few scientific studies as to its prevalence. A recent meta-analysis reviewed all previously published studies on rationing access to intensive care units but little is known about practices within the intensive care unit. Much literature in the past few years has focused on the growing use of critical care resources and projections for the future. Several authors suggest there may be a crisis in financial or personnel resources if some rationing does not take place. Other papers have argued that the methods of rationing critical care previously proposed, such as limiting the care of dying patients or using cost-effectiveness analysis to determine care, may not be effective or viewed as ethical by some. Finally, several recent papers review how critical care is practiced and allocated in India and Asian countries that already practice open rationing in their health care systems. There is currently no published evidence that overt rationing is taking place in critical care medicine. There is growing evidence that in the future, the need for critical care may outstrip financial resources unless some form of rationing takes place. It is also clear from the literature that choosing how to ration critical care will be a difficult task.

Critical Magnetic Field Strengths for Unipolar Solar Coronal Plumes In Quiet Regions and Coronal Holes?

Science.gov (United States)

Avallone, Ellis; Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; Winebarger, Amy

2017-01-01

Coronal plumes are bright magnetic funnels that are found in quiet regions and coronal holes that extend high into the solar corona whose lifetimes can last from hours to days. The heating processes that make plumes bright involve the magnetic field at the base of the plume, but their intricacies remain mysterious. Raouafi et al. (2014) infer from observation that plume heating is a consequence of magnetic reconnection at the base, whereas Wang et al. (2016) infer that plume heating is a result of convergence of the magnetic flux at the plume's base, or base flux. Both papers suggest that the base flux in their plumes is of mixed polarity, but do not quantitatively measure the base flux or consider whether a critical magnetic field strength is required for plume production. To investigate the magnetic origins of plume heating, we track plume luminosity in the 171 Å wavelength as well as the abundance and strength of the base flux over the lifetimes of six unipolar coronal plumes. Of these, three are in coronal holes and three are in quiet regions. For this sample, we find that plume heating is triggered when convergence of the base flux surpasses a field strength of approximately 300 - 500 Gauss, and that the luminosity of both quiet region and coronal hole plumes respond similarly to the strength of the magnetic field in the base.

Spin excitations and quantum criticality in the quasi-one-dimensional Ising-like ferromagnet CoCl2·2D2O in a transverse field

DEFF Research Database (Denmark)

Larsen, J.; Schäffer, T. K.; Hansen, U. B.

2017-01-01

We present experimental evidence for a quantum phase transition in the easy-axis S = 3/2 anisotropic quasione-dimensional ferromagnet CoCl2 · 2D2O in a transverse field. Elastic neutron scattering shows that the magnetic order parameter vanishes at a transverse critical field μ0Hc = 16.05(4) T......, while inelastic neutron scattering shows that the gap in the magnetic excitation spectrum vanishes at the same field value, and reopens for H>Hc. The field dependence of the order parameter and the gap are well described by critical exponents β = 0.45 ± 0.09 and zν close to 1/2, implying...... that the quantum phase transition in CoCl2 · 2D2O differs significantly from the textbook version of a S = 1/2 Ising chain in a transverse field. We attribute the difference to weak but finite three-dimensionality of the magnetic interactions....

Influence of external magnetic field, finite-size effects and chemical potential on the phase transition of a complex scalar field

Energy Technology Data Exchange (ETDEWEB)

Cavalcanti, E.; Castro, E.; Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas/MCTI, Rio de Janeiro, RJ (Brazil); Linhares, C.A. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro, RJ (Brazil)

2017-10-15

A scalar model is built, as a quantum field theory defined on a toroidal topology, to describe a phase transition in films subjected to periodic boundary conditions and influenced by an external and constant magnetic field. Criticality is studied and the relations between the critical temperature, the film thickness, the magnetic field strength and the chemical potential are investigated. Since the model describes a second-order phase transition a comparison with the Ginzburg-Landau theory is made. (orig.)

Explicitly Teaching Critical Thinking Skills in a History Course

Science.gov (United States)

McLaughlin, Anne Collins; McGill, Alicia Ebbitt

2017-01-01

Critical thinking skills are often assessed via student beliefs in non-scientific ways of thinking, (e.g, pseudoscience). Courses aimed at reducing such beliefs have been studied in the STEM fields with the most successful focusing on skeptical thinking. However, critical thinking is not unique to the sciences; it is crucial in the humanities and…

NCIS: a nuclear criticality information system

International Nuclear Information System (INIS)

Koponen, B.L.; Hampel, V.E.

1984-01-01

The NCIS is one of the developments carried out to meet the requirements in the field of criticality safety information. Its primary goal is to enhance nuclear criticality safety by dissemination of data, standards, and training material. This paper presents the ''NCIS'' progess since 1950: computer-searching, database management, nuclear critical experiments bibliography. American Nuclear Society transactions criticality safety publications compilation, edition of a personnel directory representing over 140 organizations located in 16 countries and showing a wide range of specialists involved in the field of nuclear criticality safety. The NCIS uses the information management and communication resources of TIS (Technology Information System): automated access procedures; creation of program-dependent information systems; communications. The NCIS is still in a growing, formative stage; it has concentrated first on collecting and organizing the nuclear criticality literature; nuclear critical data, calculational tools, standards, and training materials will follow. Finally the planned and contemplated resources are dealt with: expansion of bibliographic compilations; news database; fundamental criticality safety reference; criticality benchmarck database; user community; training resources; related resources; criticality accident database; dynamic databook; dynamic textbook; expert knowledge system; and, extraction of intelligence

Critical properties of Sudden Quench Dynamics in the anisotropic XY Model

OpenAIRE

Guo, Hongli; Liu, Zhao; Fan, Heng; Chen, Shu

2010-01-01

We study the zero temperature quantum dynamical critical behavior of the anisotropic XY chain under a sudden quench in a transverse field. We demonstrate theoretically that both quench magnetic susceptibility and two-particle quench correlation can be used to describe the dynamical quantum phase transition (QPT) properties. Either the quench magnetic susceptibility or the derivative of correlation functions as a function of initial magnetic field $a$ exhibits a divergence at the critical poin...

Field theory methods applied for the study of superconductivity in one-dimensional systems

International Nuclear Information System (INIS)

Martins, M.J.

1986-01-01

It is shown that the Froehlich's hamiltonian in one spatial dimension is identical to that of an exactly solvable field Theory. The spectrum of the theory is computed. A critical coupling is found above which the system becomes unstable, indicating a superconducting transition. It is also proposed and investigated a renormalizable relativistic field theory model in two space-time dimensions, with quartic self-interaction among N species of fermions, which undergoes dynamical generation of a superconducting gap and is asymptotically free. A finite temperature is introduced and, for N -> ∞ a critical value T c is found above which the gap vanishes. (author)

EDUCATIONAL TECHNOLOGY IN PRACTICE Research and Practical Case Studies from the Field

Directory of Open Access Journals (Sweden)

Reviewed by Ozden SAHIN-IZMIRLI

2010-10-01

Full Text Available The book starts with an explanation of the reason why the terms found in the book are sometimes used in place of each other. The editors stated that when technological tools are used to establish an effective and productive study process in education, the concept of learning technology is used instead of educational technology. The editors of the book considers the field as complex and vague in terms of the fact that the meanings of the concepts are close to each other in the field of educational technology and that the field provides an opportunity for inter-disciplinary studies. However, according to the editors, this vagueness and complexity shows the superiority of the field. This superiority is explained with the fact that the field of educational technology requires upper-level skills of problem solving and critical thinking and that it presents a multi-dimensional and inter-disciplinary study field. The book was edited by Wanjira Kinuthia and Steward Marshall. Wanjira Kinuthia, an assistant professor at Georgia State University, works in the Department of Middle-Secondary Education and Instructional Technology. Steward Marshall, a professor at the University of the West Indies, is the director of the Distance Education Centre. The book includes five sections and 21 chapters. These sections are “Materials, Methods, and Modalities”, “Technology Implementation and Integration Issues”, “Student Engagement and Learning”, “Building Capacity”, “Using Technology for Performance Improvement and Productivity Enhancement”.

Shift of the superconducting critical parameters due to correlated disorder

International Nuclear Information System (INIS)

Gitterman, M.; Shapiro, I.; Shapiro, B.Ya.

2012-01-01

Shift of the critical temperature and second critical magnetic field are calculated for a superconductor with Gaussian correlated disorder. All calculations have been performed in the framework of the stochastic Ginzburg-Landau equation. For uncorrelated disorder the macroscopic critical temperature is determined by the average of the local critical temperature across the sample, while for correlated disorder both the critical temperature and the upper critical magnetic field depend on disorder correlation length. In a nonuniform superconductor with randomly distributed local critical temperature both the macroscopic critical temperature and the upper critical magnetic field strongly depend on the characteristic correlation length ρ 0 of correlated disorder. The shift of the macroscopic critical parameters from those for non-correlated disorder, which does not exist for white noise, is obtained for small ρ 0 in the framework of the Ginzburg-Landau theory.

Critical currents in multilayered superconducting films

International Nuclear Information System (INIS)

Raffy, Helene

1977-01-01

The superconducting critical currents Isub(c) were measured as a function of magnetic field H and temperature T, on multilayered films. These films consist of alternating layers of two different superconductors S 1 and S 2 being a weaker superconductor acting as a flux pinning barrier region. A strong anisotropy was observed between the two situations where the magnetic field H is applied parallel or perpendicular to the layers. In the case discussed, there is a peak effect in the curves Isub(c)H well defined at the highest temperatures, and disappearing at low temperatures. The anisotropy of the critical current at constant field presents a maximum at a temperature T* close to the critical temperature Tsub(c 2 ) of S 2 [fr

Magnetization as a critical defining parameter for strand in precision dipole applications implications for field error and F-J stability

CERN Document Server

Collings, E W; Lee, E

2001-01-01

In hadron accelerators, between low energy particle injection and beam accumulation, the guiding dipoles are ramped at some rate dB/dt. Both at injection and during ramping the static and dynamic magnetizations of the magnet windings introduce multipolar distortions into the beam-line field. Dynamic magnetization, controllable by cable design, is estimated and used to provide a criterion against which to evaluate the allowable magnitude of static (persistent-current) magnetization, M, from a field-quality standpoint. The it is of NbTi and advanced Nb/sub 3/Sn conductors are compared and with regard to the latter the question of flux-jump stability is explored. A magnetization criterion for such stability is presented and compared to experiment. It is noted that since Delta M is proportional to critical current density, J/sub c/, and the strand's effective filament diameter, d/sub eff/, the latter has frequently been specified as a critical parameter, although it will need to be re-specified with every increas...

Backreacted axion field ranges in string theory

Energy Technology Data Exchange (ETDEWEB)

Baume, Florent; Palti, Eran [Institut für Theoretische Physik, Ruprecht-Karls-Universität, Philosophenweg 19, Heidelberg, 69120 (Germany)

2016-08-05

String theory axions are interesting candidates for fields whose potential might be controllable over super-Planckian field ranges and therefore as possible candidates for inflatons in large field inflation. Axion monodromy scenarios are setups where the axion shift symmetry is broken by some effect such that the axion can traverse a large number of periods potentially leading to super-Planckian excursions. We study such scenarios in type IIA string theory where the axion shift symmetry is broken by background fluxes. In particular we calculate the backreaction of the energy density induced by the axion vacuum expectation value on its own field space metric. We find universal behaviour for all the compactifications studied where up to a certain critical axion value there is only a small backreaction effect. Beyond the critical value the backreaction is strong and implies that the proper field distance as measured by the backreacted metric increases at best logarithmically with the axion vev, thereby placing strong limitations on extending the field distance any further. The critical axion value can be made arbitrarily large by the choice of fluxes. However the backreaction of these fluxes on the axion field space metric ensures a precise cancellation such that the proper field distance up to the critical axion value is flux independent and remains sub-Planckian. We also study an axion alignment scenario for type IIA compactifications on a twisted torus with four fundamental axions mixing to leave an axion with an effective decay constant which is flux dependent. There is a choice of fluxes for which the alignment parameter controlling the effective decay constant is unconstrained by tadpoles and can in principle lead to an arbitrarily large effective decay constant. However we show that these fluxes backreact on the fundamental decay constants so as to precisely cancel any enhancement leaving a sub-Planckian effective decay constant.

Critical Literacy: Foundational Notes

Science.gov (United States)

Luke, Allan

2012-01-01

The term "critical literacy" refers to use of the technologies of print and other media of communication to analyze, critique, and transform the norms, rule systems, and practices governing the social fields of everyday life (A. Luke, 2004). Since Freire's (1970) educational projects in Brazil, approaches to critical literacy have been…

Games and Metaphor - A critical analysis of the metaphor discourse in game studies

DEFF Research Database (Denmark)

Möring, Sebastian Martin

This doctoral dissertation critically investigates how the concept of metaphor is used with regard to games in game studies. The goal is to provide the field with a self-understanding of its metaphor discourse which has not been researched so far. The thesis departs from the observation...... and game theory, cultural theory, semiotics, linguistics, philosophy, and game studies it investigates the metaphor discourse of game studies in the fashion of a meta-study. The main part of this thesis is devoted to three particular problems which have been derived from observations in the overview...... of the current use of the notion of metaphor in game studies. Firstly, this thesis investigates is the conceptual relationship between the notions of metaphor, representation, and play. It therefore accounts for observations such that all three notions are present in non-computer game and play theory, theory...

A fundamental study of a variable critical nozzle flow

International Nuclear Information System (INIS)

Kim, Jea Hyung; Kim, Heuy Dong; Park, Kyung Am

2003-01-01

The mass flow rate of gas flow through critical nozzle depends on the nozzle supply conditions and the cross-sectional area at the nozzle throat. In order that the critical nozzle can be operated at a wide range of supply conditions, the nozzle throat diameter should be controlled to change the flow passage area. This can be achieved by means of a variable critical nozzle. In the present study, both experimental and computational works are performed to develop variable critical nozzle. A cone-cylinder with a diameter of d is inserted into conventional critical nozzle. It can move both upstream and downstream, thereby changing the cross-sectional area of the nozzle throat. Computational work using the axisymmetric, compressible Navier-Stokes equations is carried out to simulate the variable critical nozzle flow. An experiment is performed to measure the mass flow rate through variable critical nozzle. The present computational results are in close agreement with measured ones. The boundary layer displacement and momentum thickness are given as a function of Reynolds number. An empirical equation is obtained to predict the discharge coefficient of variable critical nozzle

Phase transitions and critical phenomena

CERN Document Server

Domb, Cyril

2001-01-01

The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in

Critical Studies in Teaching and Learning

African Journals Online (AJOL)

Critical Studies in Teaching and Learning is a peer-reviewed journal that publishes scholarly articles and essays that make marked contributions to the scholarship of teaching and learning in higher education. The Journal aims to provide a stimulating and challenging forum for contributors to describe, theorise and reflect ...

Criticality studies; Etudes de criticite

Energy Technology Data Exchange (ETDEWEB)

Breton, D; Lecorche, P; Clouet d' Orval, Ch [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

Criticality studies made at the Commissariat a l'Energie atomique deal on the one hand with experiments on plutonium and uranium solutions, on the other hand with theoretical work on the development and use of computation, methods for the resolution of problems concerning the nuclear safety of chemical and metallurgical plants. I - Since 1958 the experimental studies have dealt with homogeneous media constituted by a fissile salt dissolved in light water. Developed using the reactor Proserpine, the experiments have been carried on at Saclay on the Alecto assemblies where solutions of plutonium or of 90 p.100 - enriched uranium can be made critical. The results already obtained relate to critical masses of cylindrical tanks of diameters from 20 to 50 cm. reflected in several ways (water, concrete, etc. . ) at concentrations up to 100 g/liter. Physical measurements (spectra, reactor noises) and interaction measurements complete the results. Other experiments relating to plutonium solutions were begun in 1963, at the Valduc Center. They deal with the study of critical masses of annular vessels of external diameter 50 cm and internal diameter varying from 10 to 30 cm. These vessels can be water reflected internally, externally, or both. Two of these vessels have been studied in interaction for various geometries. Slabs of various thicknesses were also studied. II - The studies thus undertaken allowed the development of methods of computation which have been tested on several experiments. Particular use has been made of the possibilities of calculations based on transport theory and on Monte Carlo methods. All these theoretical studies are applied to the design and control of industrial plants from the point of view of safety. (authors) [French] Les etudes de criticite effectuees au CEA comportent d'une part des experiences sur des solutions de plutonium et d'uranium enrichi, d'autre part des travaux theoriques portant sur la mise au point et l'exploitation de methodes

Experimental and numerical study of influence of ferromagnetic cover on critical current of BiSCCO-2223/Ag tape superconductor

International Nuclear Information System (INIS)

Vojenciak, M; Souc, J; Goemoery, F

2009-01-01

Samples of commercially available BiSCCO-2223/Ag tape have been partially covered by the ferromagnetic material. Improvement of the self-field critical current up to 15 % has been achieved by this procedure. A critical current of such tape strongly depends on geometric and magnetic properties of both, the superconducting tape as well as the ferromagnetic cover. Numerical simulations, based on the critical state model using commercial finite element method (FEM) code, have been performed. Properties of superconductor are characterized by anisotropic dependence of the critical current density on magnetic field as well as detail geometry of filaments. The ferromagnetic material is characterized by nonlinear magnetization curve. Nonlinear dependences of the critical current on selected parameters are shown in this work. Optimization of the cover parameters using these curves has been made. Samples with various parameters have been manufactured for the confirmation of numerical simulations results. Experimental results are in good qualitative agreement with results obtained by numerical simulations.

Chiral spiral induced by a strong magnetic field

Directory of Open Access Journals (Sweden)

Abuki Hiroaki

2016-01-01

Full Text Available We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it brings a “continent” of chiral spiral in the phase diagram, by which the chiral tricritical point is totally washed out. This is the case no matter how small the intensity of magnetic field is. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However, the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

Evolution of the two-gap nature revealed in the upper critical field of Mg1-xAlxB2

International Nuclear Information System (INIS)

Kim, Heon-Jung; Lee, Hyun-Sook; Park, Min-Seok; Lee, H.-G.; Jo, Younghun; Jung, Myung-Hwa; Lee, Sung-Ik; Kang, Byeongwon

2007-01-01

The temperature and the angular dependences of the upper critical field [H c2 (T,θ)] of Mg 1-x Al x B 2 single crystals (x=0.12 and 0.21) were studied. The H c2 (T,θ) was found to be well described by the dirty-limit two-gap theory. A quantitative comparison of the data with this theory indicated that Mg 1-x Al x B 2 single crystals preserved the two-gap nature but became dirtier. We also found that as the Al concentration was increased, anisotropic impurity scattering increased, making the σ bands less anisotropic. In addition, these results are compared with those of 10% C-doped MgB 2 single crystals

Orbital and spin effects for the upper critical field in As-deficient disordered Fe pnictide superconductors

International Nuclear Information System (INIS)

Fuchs, G; Drechsler, S-L; Kozlova, N; Hamann-Borrero, J E; Behr, G; Nenkov, K; Freudenberger, J; Koehler, A; Knupfer, M; Buechner, B; Schultz, L; Bartkowiak, M; Klauss, H-H; Maeter, H; Kwadrin, A; Amato, A; Luetkens, H; Khasanov, R; Arushanov, E; Rosner, H

2009-01-01

We report upper critical field B c2 (T) data for LaO 0.9 F 0.1 FeAs 1-δ in a wide temperature and field range up to 60 T. The large slope of B c2 ∼- 5.4 to -6.6 T K -1 near an improved T c ∼28.5 K of the in-plane B c2 (T) contrasts with a flattening starting near 23 K above 30 T we regard as the onset of Pauli-limited behaviour (PLB) with B c2 (0)∼63-68 T. We interpret a similar hitherto unexplained flattening of the B c2 (T) curves reported for at least three other disordered closely related systems, Co-doped BaFe 2 As 2 , (Ba,K) Fe 2 As 2 and NdO 0.7 F 0.3 FeAs (all single crystals), for applied fields H parallel (a,b), also as a manifestation of PLB. Their Maki parameters have been estimated by analysing their B c2 (T) data within the Werthamer-Helfand-Hohenberg approach. The pronounced PLB of (Ba, K)Fe 2 As 2 single crystals obtained from an Sn flux is attributed also to a significant As deficiency detected by wavelength dispersive x-ray spectroscopy as reported by Ni et al (2008 Phys. Rev. B 78 014507). Consequences of our results are discussed in terms of disorder effects within conventional superconductivity (CSC) and unconventional superconductivity (USC). USC scenarios with nodes on individual Fermi surface sheets (FSS), e.g. p- and d-wave SC, can be discarded for our samples. The increase of dB c2 /dT| T c by sizeable disorder provides evidence for an important intraband (intra-FSS) contribution to the orbital upper critical field. We suggest that it can be ascribed either to an impurity-driven transition from s ± USC to CSC of an extended s ++ -wave state or to a stabilized s ± -state provided As-vacancies cause predominantly strong intraband scattering in the unitary limit. We compare our results with B c2 data from the literature, which often show no PLB for fields below 60-70 T probed so far. A novel disorder-related scenario of a complex interplay of SC with two different competing magnetic instabilities is suggested.

Multi-band description of the specific heat and thermodynamic critical field in MgB2 superconductor

Science.gov (United States)

Szcześniak, R.; Jarosik, M. W.; Tarasewicz, P.; Durajski, A. P.

2018-05-01

The thermodynamic properties of MgB2 superconductor can be explained using the multi-band models. In the present paper we have examined the experimental data available in literature and we have found out that it is possible to reproduce the measured values of the superconducting energy gaps, the thermodynamic critical magnetic field and specific heat jump within the framework of two-band Eliashberg formalism and appropriate defined free energy difference between superconducting and normal state. Moreover, we found that the obtained results differ significantly from the predictions of the conventional Bardeen-Cooper-Schrieffer theory.

A study on critical heat flux in gap

Energy Technology Data Exchange (ETDEWEB)

Park, Rae Joon; Jeong, Ji Whan; Cho, Young Ro; Chang, Young Cho; Kang, Kyung Ho; Kim, Jong Whan; Kim, Sang Baik; Kim, Hee Dong

1999-04-01

The scope and content of this study is to perform the test on critical heat flux in hemispherical narrow gaps using distilled water and Freon R-113 as experimental parameters, such as system pressure from 1 to 10 atm and gap thickness of 0.5, 1.0, 2.0, and 5.0 mm. The CHFG test results have shown that the measured values of critical power are much lower than the predictions made by empirical CHF correlations applicable to flat plate gaps and annuli. The pressure effect on the critical power was found to be much milder than predictions by those CHF correlations. The values and the pressure trend of the critical powers measured in the present experiments are close to the values converted from the CCFL data. This confirms the claim that a CCFL brings about local dryout and finally, global dryout in hemispherical narrow gaps. Increases in the gap thickness lead to increase in critical power. The measured critical power using R-113 in hemispherical narrow gaps are 60 % lower than that using water due to the lower boiling point, which is different from the pool boiling condition. The CCFL (counter counter flow limit) test facility was constructed and the test is being performed to estimate the CCFL phenomena and to evaluate the CHFG test results on critical power in hemispherical narrow gaps. (Author). 35 refs., 2 tabs., 19 figs.

A study on critical heat flux in gap

International Nuclear Information System (INIS)

Park, Rae Joon; Jeong, Ji Whan; Cho, Young Ro; Chang, Young Cho; Kang, Kyung Ho; Kim, Jong Whan; Kim, Sang Baik; Kim, Hee Dong

1999-04-01

The scope and content of this study is to perform the test on critical heat flux in hemispherical narrow gaps using distilled water and Freon R-113 as experimental parameters, such as system pressure from 1 to 10 atm and gap thickness of 0.5, 1.0, 2.0, and 5.0 mm. The CHFG test results have shown that the measured values of critical power are much lower than the predictions made by empirical CHF correlations applicable to flat plate gaps and annuli. The pressure effect on the critical power was found to be much milder than predictions by those CHF correlations. The values and the pressure trend of the critical powers measured in the present experiments are close to the values converted from the CCFL data. This confirms the claim that a CCFL brings about local dryout and finally, global dryout in hemispherical narrow gaps. Increases in the gap thickness lead to increase in critical power. The measured critical power using R-113 in hemispherical narrow gaps are 60 % lower than that using water due to the lower boiling point, which is different from the pool boiling condition. The CCFL (counter counter flow limit) test facility was constructed and the test is being performed to estimate the CCFL phenomena and to evaluate the CHFG test results on critical power in hemispherical narrow gaps. (Author). 35 refs., 2 tabs., 19 figs

Simulation study of the ionizing front in the critical ionization velocity phenomenon

International Nuclear Information System (INIS)

Machida, S.; Goertz, C.K.; Lu, G.

1988-01-01

Simulations of the Critical Ionization Velocity (CIV) for a neutral gas cloud moving across the static magnetic field are made. We treat a low-β plasma and use a 2-1/2 D electrostatic code linked with our Plasma and Neutral Interaction Code (PANIC). Our study is focused on the understanding of the interface between the neutral gas cloud and the surrounding plasma where the strong interaction takes place. We assume the existence of some hot electrons in the ambient plasma to provide a seed ionization for CIV. When the ionization starts a sheath-like structure is formed at the surface of the neutral gas (Ionizing Front). In that region the crossfield component of the electric field causes the electron to E x B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. Thus the kinetic energy of the drifting electrons can be large enough for electron impact ionization. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the ionization front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating and additional ionization. The overall structure is studied by developing a simple analytic model as well as making simulation runs. (author)

Case Study in Public Administration: A Critical Review of Brazilian Scientific Production

Directory of Open Access Journals (Sweden)

Mariana Guerra

2015-03-01

Full Text Available This paper presents a critical review of 47 articles published between 2006 and 2011 to identify how case studies have been applied in Brazilian research on public administration. In addition to their theoretical and methodological characteristics, four further specific topics of interest were addressed: (a what is meant by case study; (b the relationship between the phenomenon of interest and the case under investigation; (c the possibility of replication; and (d how the supposed method contributes towards the development of the field of public administration. The main inconsistencies found were: the methodological descriptions are confusing; the results are inconsistent compared with data gathering procedures and data analysis techniques; a lack of information about the number of interviewed individuals; and no descriptions of research variables. The results suggest the reviewed case studies present methodological inconsistencies and limitations, which undermine their scientific value and relevance to academic work in Brazil.

Entanglement of two blocks of spins in the critical Ising model

Science.gov (United States)

Facchi, P.; Florio, G.; Invernizzi, C.; Pascazio, S.

2008-11-01

We compute the entropy of entanglement of two blocks of L spins at a distance d in the ground state of an Ising chain in an external transverse magnetic field. We numerically study the von Neumann entropy for different values of the transverse field. At the critical point we obtain analytical results for blocks of size L=1 and 2. In the general case, the critical entropy is shown to be additive when d→∞ . Finally, based on simple arguments, we derive an expression for the entropy at the critical point as a function of both L and d . This formula is in excellent agreement with numerical results.

Notes on analytical study of holographic superconductors with Lifshitz scaling in external magnetic field

International Nuclear Information System (INIS)

Zhao, Zixu; Pan, Qiyuan; Jing, Jiliang

2014-01-01

We employ the matching method to analytically investigate the holographic superconductors with Lifshitz scaling in an external magnetic field. We discuss systematically the restricted conditions for the matching method and find that this analytic method is not always powerful to explore the effect of external magnetic field on the holographic superconductors unless the matching point is chosen in an appropriate range and the dynamical exponent z satisfies the relation z=d−1 or z=d−2. From the analytic treatment, we observe that Lifshitz scaling can hinder the condensation to be formed, which can be used to back up the numerical results. Moreover, we study the effect of Lifshitz scaling on the upper critical magnetic field and reproduce the well-known relation obtained from Ginzburg–Landau theory

Methods for studying plasma charge transport across a magnetic field

International Nuclear Information System (INIS)

Popovich, A.S.

1978-01-01

A comparative analysis of experimental methods for the diffusion transfer of plasma charged particles accross the magnetic field at the study of its confinement effectiveness, instability effect is carried out. Considered are the methods based on the analysis of particle balance in the charge and possibilities of diffusion coefficient determination according to measuring parameters of density gradient and particle flow on the wall, rate of plasma decay after switching off ionization source radial profile of plasma density outside the active region of stationary charge. Much attension is payed to the research methods of diffusion transfer, connected with the study of propagation of periodic and aperiodic density perturbation in a plasma. Analysed is the Golubev and Granovsky method of diffusion waves and its different modifications, phase analysis method of ''test charges'' movement, as well as different modifications of correlation methods. Considered are physical preconditions of the latter and criticized is unilateral interpretation of correlation measurings, carried out in a number of works. The analysis of study possibilities of independent (non-ambipolar) diffusion of electrons and ions in a plasma in the magnetic field is executed

The Construction of the Migration’s Field of Study in Chile: Notes of a Reflexive and Self-Critical Exercise

Directory of Open Access Journals (Sweden)

Carolina Stefoni

2017-05-01

Full Text Available Along with the growth of the international migration over the last 20 years in Chile, there has been a steady increase in scientific research and publications. This academic interest has allowed the development of a field of studies that is characterized, as every field is, by a certain accumulation of knowledge, thematic diversification, theoretical discussion, approaches from different disciplines and delimitation of particular forms. The interest of this article is to analyze the scientific production on migration in Chile during this period, using two approaches: one thematic and the other analytical. In the results of this work, a reflection on the way in which the category of migration is constructed from the field of social sciences in the country and a possible thematic agenda is presented for future research.

Studying Irony Detection Beyond Ironic Criticism: Let's Include Ironic Praise

Directory of Open Access Journals (Sweden)

Richard Bruntsch

2017-04-01

Full Text Available Studies of irony detection have commonly used ironic criticisms (i.e., mock positive evaluation of negative circumstances as stimulus materials. Another basic type of verbal irony, ironic praise (i.e., mock negative evaluation of positive circumstances is largely absent from studies on individuals' aptitude to detect verbal irony. However, it can be argued that ironic praise needs to be considered in order to investigate the detection of irony in the variety of its facets. To explore whether the detection ironic praise has a benefit beyond ironic criticism, three studies were conducted. In Study 1, an instrument (Test of Verbal Irony Detection Aptitude; TOVIDA was constructed and its factorial structure was tested using N = 311 subjects. The TOVIDA contains 26 scenario-based items and contains two scales for the detection of ironic criticism vs. ironic praise. To validate the measurement method, the two scales of the TOVIDA were experimentally evaluated with N = 154 subjects in Study 2. In Study 3, N = 183 subjects were tested to explore personality and ability correlates of the two TOVIDA scales. Results indicate that the co-variance between the ironic TOVIDA items was organized by two inter-correlated but distinct factors: one representing ironic praise detection aptitude and one representing ironic criticism detection aptitude. Experimental validation showed that the TOVIDA items truly contain irony and that item scores reflect irony detection. Trait bad mood and benevolent humor (as a facet of the sense of humor were found as joint correlates for both ironic criticism and ironic praise detection scores. In contrast, intelligence, trait cheerfulness, and corrective humor were found as unique correlates of ironic praise detection scores, even when statistically controlling for the aptitude to detect ironic criticism. Our results indicate that the aptitude to detect ironic praise can be seen as distinct from the aptitude to detect ironic

Quantum criticality among entangled spin chains

Science.gov (United States)

Blanc, N.; Trinh, J.; Dong, L.; Bai, X.; Aczel, A. A.; Mourigal, M.; Balents, L.; Siegrist, T.; Ramirez, A. P.

2018-03-01

An important challenge in magnetism is the unambiguous identification of a quantum spin liquid1,2, of potential importance for quantum computing. In such a material, the magnetic spins should be fluctuating in the quantum regime, instead of frozen in a classical long-range-ordered state. While this requirement dictates systems3,4 wherein classical order is suppressed by a frustrating lattice5, an ideal system would allow tuning of quantum fluctuations by an external parameter. Conventional three-dimensional antiferromagnets can be tuned through a quantum critical point—a region of highly fluctuating spins—by an applied magnetic field. Such systems suffer from a weak specific-heat peak at the quantum critical point, with little entropy available for quantum fluctuations6. Here we study a different type of antiferromagnet, comprised of weakly coupled antiferromagnetic spin-1/2 chains as realized in the molecular salt K2PbCu(NO2)6. Across the temperature-magnetic field boundary between three-dimensional order and the paramagnetic phase, the specific heat exhibits a large peak whose magnitude approaches a value suggestive of the spinon Sommerfeld coefficient of isolated quantum spin chains. These results demonstrate an alternative approach for producing quantum matter via a magnetic-field-induced shift of entropy from one-dimensional short-range order to a three-dimensional quantum critical point.

Upper critical field and vortices in S/F bilayers exhibiting the quasi-onedimensional FFLO-like state

Energy Technology Data Exchange (ETDEWEB)

Lenk, Daniel; Hemmida, Mamoun; Kehrle, Jan; Zdravkov, Vladimir I.; Ullrich, Aladin; Obermeier, Guenther; Mueller, Claus; Loidl, Alois; Krug von Nidda, Hans-Albrecht; Horn, Siegfried; Tidecks, Reinhard [Institut fuer Physik, Universitaet Augsburg (Germany); Morari, Roman [Institut fuer Physik, Universitaet Augsburg (Germany); D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Kishinev (Moldova, Republic of); Sidorenko, Anatolie S. [D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM, Kishinev (Moldova, Republic of); Tagirov, Lenar [Institut fuer Physik, Universitaet Augsburg (Germany); Solid State Physics Department, Kazan Federal University (Russian Federation)

2015-07-01

We investigate the temperature dependence of the upper critical field, B{sub c2}, in superconductor/ferromagnet (S/F) bilayers as a function of the F-layer thickness, d{sub F}, by resistance measurements. We extracted GL coherence lengths and estimated an effective thickness of the superconducting layer by evaluating the perpendicular coherence length at the 3D-2D crossover temperature in the parallel B{sub c2}. We found an unexpected non-monotonous behavior of the effective thickness as a function of d{sub F}. Moreover, we investigated the anisotropy of B{sub c2} by microwave absorption. The results show a deviation from Tinkham's prediction for thin films, which we attribute to the additional anisotropy induced by the quasi-1D FFLO-like state. Thus, we propose a new type of vortex, developing in the S/F bilayer in magnetic fields applied close to parallel.

On the prospects of increasing critical parameters of superconductors

International Nuclear Information System (INIS)

Lazarev, B.G.; Pan, V.M.

1979-01-01

Noted is the importance of the production of materials with high critical parameters for modern science and technology. Considered are present notions about the nature of high critical densities of critical current. The opinion is expressed that the search of most high-temperature and high-field superconductors should be carried out, in the first place, among compounds based on transition metals displaying structural instability. Noted are prospects of the work over the synthesis of metastabile compounds with A15 structure (e.g. Nb 3 Si), three-component and more complex compounds, and superconductive amorphous systems(metglasses). It is emphasized that the exceeding of the paramagnetic limit of the critical magnetic field is often observed experimentally, and the prospects of critical field increase are sufficiently favourable. Considered is the role of narrow current channels in the formation of critical current density of superconductors

A review of costing methodologies in critical care studies.

Science.gov (United States)

Pines, Jesse M; Fager, Samuel S; Milzman, David P

2002-09-01

Clinical decision making in critical care has traditionally been based on clinical outcome measures such as mortality and morbidity. Over the past few decades, however, increasing competition in the health care marketplace has made it necessary to consider costs when making clinical and managerial decisions in critical care. Sophisticated costing methodologies have been developed to aid this decision-making process. We performed a narrative review of published costing studies in critical care during the past 6 years. A total of 282 articles were found, of which 68 met our search criteria. They involved a mean of 508 patients (range, 20-13,907). A total of 92.6% of the studies (63 of 68) used traditional cost analysis, whereas the remaining 7.4% (5 of 68) used cost-effectiveness analysis. None (0 of 68) used cost-benefit analysis or cost-utility analysis. A total of 36.7% (25 of 68) used hospital charges as a surrogate for actual costs. Of the 43 articles that actually counted costs, 37.2% (16 of 43) counted physician costs, 27.9% (12 of 43) counted facility costs, 34.9% (15 of 43) counted nursing costs, 9.3% (4 of 43) counted societal costs, and 90.7% (39 of 43) counted laboratory, equipment, and pharmacy costs. Our conclusion is that despite considerable progress in costing methodologies, critical care studies have not adequately implemented these techniques. Given the importance of financial implications in medicine, it would be prudent for critical care studies to use these more advanced techniques. Copyright 2002, Elsevier Science (USA). All rights reserved.

Quantum critical dynamics for a prototype class of insulating antiferromagnets

Science.gov (United States)

Wu, Jianda; Yang, Wang; Wu, Congjun; Si, Qimiao

2018-06-01

Quantum criticality is a fundamental organizing principle for studying strongly correlated systems. Nevertheless, understanding quantum critical dynamics at nonzero temperatures is a major challenge of condensed-matter physics due to the intricate interplay between quantum and thermal fluctuations. The recent experiments with the quantum spin dimer material TlCuCl3 provide an unprecedented opportunity to test the theories of quantum criticality. We investigate the nonzero-temperature quantum critical spin dynamics by employing an effective O (N ) field theory. The on-shell mass and the damping rate of quantum critical spin excitations as functions of temperature are calculated based on the renormalized coupling strength and are in excellent agreement with experiment observations. Their T lnT dependence is predicted to be dominant at very low temperatures, which will be tested in future experiments. Our work provides confidence that quantum criticality as a theoretical framework, which is being considered in so many different contexts of condensed-matter physics and beyond, is indeed grounded in materials and experiments accurately. It is also expected to motivate further experimental investigations on the applicability of the field theory to related quantum critical systems.

Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering

International Nuclear Information System (INIS)

Gurevich, A; Patnaik, S; Braccini, V; Kim, K H; Mielke, C; Song, X; Cooley, L D; Bu, S D; Kim, D M; Choi, J H; Belenky, L J; Giencke, J; Lee, M K; Tian, W; Pan, X Q; Siri, A; Hellstrom, E E; Eom, C B; Larbalestier, D C

2004-01-01

We report a significant enhancement of the upper critical field H c2 of different MgB 2 samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities ρ, we show a clear trend of an increase in H c2 as ρ increases. One particular high resistivity film had a zero-temperature H c2 (0) well above the H c2 values of competing non-cuprate superconductors such as Nb 3 Sn and Nb-Ti. Our high-field transport measurements give record values H c2 perp (0) ∼ 34 T and H c2 par (0) ∼ 49 T for high resistivity films and H c2 (0) ∼ 29 T for untextured bulk polycrystals. The highest H c2 film also exhibits a significant upward curvature of H c2 (T) and a temperature dependence of the anisotropy parameter γ(T)=H c2 par / H c2 opposite to that of single crystals: γ(T) decreases as the temperature decreases, from γ(T c ) ∼ 2 γ(0) ∼ 1.5. This remarkable H c2 enhancement and its anomalous temperature dependence are a consequence of the two-gap superconductivity in MgB 2 , which offers special opportunities for further H c2 increases by tuning of the impurity scattering by selective alloying on Mg and B sites. Our experimental results can be explained by a theory of two-gap superconductivity in the dirty limit. The very high values of H c2 (T) observed suggest that MgB 2 can be made into a versatile, competitive high-field superconductor

Studies on Nb3Sn field coils for superconducting machine

International Nuclear Information System (INIS)

Fujino, H.; Nose, S.

1981-01-01

This paper describes experimental studies on several coils wound with multifilamentary (MF) Nb 3 Sn cables with reinforcing strip for superconducting rotating machine application. To use a Nb 3 Sn superconductor to field winding of a rotating machine, several coil performances of pre-reacted, bronze processed and stranded MF Nb 3 Sn cables were investigated, mainly in relation to stress effect. Bending strain up to 0.64% in strand and winding stress of 5 kg/mm 2 have resulted in nondegradation in coil performance. A pair of impregnated race-track coils designed for a 30 MVA synchronous condenser was energized successfully up to 80% of critical current without quench. 8 refs

Social Ecology and Aesthetic Criticism

Directory of Open Access Journals (Sweden)

Owen, Connor

2016-12-01

Full Text Available While ecocriticism has become a respected field in literary theory and in the broader landscape of aesthetic philosophy, it could benefit from an enhanced ethical-political framework which social ecology – an underrated critical theory developed by Murray Bookchin – could provide. This essay attempts to tease out the potentials for such a framework, integrating the insights of social ecology, ecocriticism, Critical Realism, and John Dewey's aesthetic concepts into a layered idea-set used for the study of all kinds of aesthetic objects, from popular art to the gallery arts. Its key principles are the emergence of aesthetic objects (including formal artworks out of congealed human experience, the relation between organism and environment in assessing meaning, the breakdown of implicit or overt hierarchies within a work, and the idea of the artist and art-critic as a "gardener".

Hypernuclear matter in strong magnetic field

Energy Technology Data Exchange (ETDEWEB)

Sinha, Monika [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany); Indian Institute of Technology Rajasthan, Old Residency Road, Ratanada, Jodhpur 342011 (India); Mukhopadhyay, Banibrata [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Sedrakian, Armen, E-mail: sedrakian@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany)

2013-01-17

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10{sup 14}–10{sup 15} G, the implied internal field strength being several orders larger. We study the equation of state and composition of dense hypernuclear matter in strong magnetic fields in a range expected in the interiors of magnetars. Within the non-linear Boguta–Bodmer–Walecka model we find that the magnetic field has sizable influence on the properties of matter for central magnetic field B⩾10{sup 17} G, in particular the matter properties become anisotropic. Moreover, for the central fields B⩾10{sup 18} G, the magnetized hypernuclear matter shows instability, which is signalled by the negative sign of the derivative of the pressure parallel to the field with respect to the density, and leads to vanishing parallel pressure at the critical value B{sub cr}≃10{sup 19} G. This limits the range of admissible homogeneously distributed fields in magnetars to fields below the critical value B{sub cr}.

Phase transitions and critical phenomena

CERN Document Server

Domb, Cyril

2000-01-01

The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m

Dynamical mass generation in QED with weak magnetic fields

International Nuclear Information System (INIS)

Ayala, A.; Rojas, E.; Bashir, A.; Raya, A.

2006-01-01

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2

Calculational study for criticality safety data of fissionable actinides

International Nuclear Information System (INIS)

Nojiri, Ichiro; Fukasaku, Yasuhiro.

1997-01-01

This study has been carried out to obtain basic criticality safety characteristics of minor actinides nuclides. Criticality safety data of minor actinides nuclides have been surveyed through public literatures. Critical mass of seven nuclides, Np-237, Am-241, Am-242m, Am-243, Cm-243, Cm-244 and Cm-245, have been calculated by using two code systems of criticality safety analysis, SCALE-4 and MCNP4A, under some material and reflector conditions. Some applicable cross-section libraries have been used for each code systems. Calculated data have been compared with each other and with published data. The results of this comparison shows that there is no discrepancy within the computational codes and the calculated data is strongly depend on the cross-section library. (author)

A statistical study of current-sheet formation above solar active regions based on selforganized criticality

Science.gov (United States)

Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M.; Anastasiadis, A.; Toutountzi, A.

2013-09-01

We treat flaring solar active regions as physical systems having reached the self-organized critical state. Their evolving magnetic configurations in the low corona may satisfy an instability criterion, related to the excession of a specific threshold in the curl of the magnetic field. This imposed instability criterion implies an almost zero resistivity everywhere in the solar corona, except in regions where magnetic-field discontinuities and. hence, local currents, reach the critical value. In these areas, current-driven instabilities enhance the resistivity by many orders of magnitude forming structures which efficiently accelerate charged particles. Simulating the formation of such structures (thought of as current sheets) via a refined SOC cellular-automaton model provides interesting information regarding their statistical properties. It is shown that the current density in such unstable regions follows power-law scaling. Furthermore, the size distribution of the produced current sheets is best fitted by power laws, whereas their formation probability is investigated against the photospheric magnetic configuration (e.g. Polarity Inversion Lines, Plage). The average fractal dimension of the produced current sheets is deduced depending on the selected critical threshold. The above-mentioned statistical description of intermittent electric field structures can be used by collisional relativistic test particle simulations, aiming to interpret particle acceleration in flaring active regions and in strongly turbulent media in astrophysical plasmas. The above work is supported by the Hellenic National Space Weather Research Network (HNSWRN) via the THALIS Programme.

Correlation between in-field critical currents in Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes at 30 and 77 K

International Nuclear Information System (INIS)

Selvamanickam, V; Xu, A; Liu, Y; Khatri, N D; Galstyan, E; Majkic, G; Lei, C; Chen, Y

2014-01-01

Critical current (I c ) values of 1384 A/12 mm, corresponding to a critical current density of 12.47 MA cm −2 and a pinning force of 374 GN m −3 , have been achieved at 30 K, 3 T in the orientation of field parallel to the c axis (B ∥ c) in (Gd, Y)BaCuO tapes with 15 mol% Zr addition made by metal organic chemical vapor deposition (MOCVD). These tapes show pinning force levels as high as 453 GN m −3 at 30 K. An analysis of the properties of 24–28 (Gd, Y)BaCuO tapes with 15 mol% Zr addition showed a lack of correlation between their critical currents at 30 K, 3 T (B ∥ c) and I c values both at 77 K, zero field and at 77 K, 1 T (B ∥ c). However, a strong correlation was found between the critical currents at 30 K, 3 T and at 77 K, 3 T (B ∥ c). It has also been discovered that the minimum critical current (I c, min ) value at 77 K, 3 T has no influence on the I c, min value at 30 K, 3 T, and it in turn depends on the ratio of the I c values in the orientations of field parallel and perpendicular to the c axis at 77 K, 3 T. (paper)

Effects of mixing and stirring on the critical behaviour

International Nuclear Information System (INIS)

Antonov, N V; Hnatich, Michal; Honkonen, Juha

2006-01-01

Stochastic dynamics of a nonconserved scalar order parameter near its critical point, subject to random stirring and mixing, is studied using the field-theoretic renormalization group. The stirring and mixing are modelled by a random external Gaussian noise with the correlation function ∼δ(t - t')k 4-d-y and the divergence-free (due to incompressibility) velocity field, governed by the stochastic Navier-Stokes equation with a random Gaussian force with the correlation function ∝ δ(t-t')k 4-d-y' . Depending on the relations between the exponents y and y' and the space dimensionality d, the model reveals several types of scaling regimes. Some of them are well known (model A of equilibrium critical dynamics and linear passive scalar field advected by a random turbulent flow), but there are three new non-equilibrium regimes (universality classes) associated with new nontrivial fixed points of the renormalization group equations. The corresponding critical dimensions are calculated in the two-loop approximation (second order of the triple expansion in y, y' and ε = 4 - d)

Comparison between 3D dynamics filter technique, field-in-field, electronic compensator in breast cancer; Comparacao entre tecnica 3D com filtro dinamico, field-in-field e compensacao eletronica para cancer de mama

Energy Technology Data Exchange (ETDEWEB)

Trindade, Cassia; Silva, Leonardo P.; Martins, Lais P.; Garcia, Paulo L.; Santos, Maira R.; Bastista, Delano V.S.; Vieira, Anna Myrian M.T.L.; Rocha, Igor M., E-mail: cassiatr@gmail.com [Instituto Nacional de Cancer (INCA), Rio de Janeiro, RJ (Brazil)

2012-12-15

The radiotherapy has been used in a wild scale in breast cancer treatment. With this high demand, new technologies have been developed to improve the dose distribution in the target while reducing the dose delivered in critical organs. In this study, performed with one clinical case, three planning were done for comparison: 3D technique with dynamic filter, 3D with field-in-field technique (forward-planned IMRT) and 3D technique using electronic compensator (ECOMP). The planning were done with a 6MV photon beam using the Eclipse software, version 8.6 (Varian Medical Systems). The PTV was drawn covering the whole breast and the critical organs were: the lung on the irradiated side, the heart, the contralateral breast and the anterior descending coronary artery (LAD). The planning using the compensator technique permitted more homogeneous dose distribution in the target volume. The V20 value of the lung on the irradiated side was 8,3% for the electronic compensator technique, 8,9% for the field-in-field technique and 8,2% for the dynamic filter technique. For the heart the dose range was 15.7 - 139.9 cGy, 16.3 - 148.4 cGy for the dynamic filter technique and 19.6 - 157.0 cGy for the field-in-field technique. The dose gradient was 11% with compensator electronic, 15% dynamic filter technique and 13% with field-in-field. The application of electronic technique in breast cancer treatment allows better dose distribution while reduces dose in critical organs, but in the same time requires a quality assurance. (author)

Reversal of the Upper Critical Field Anisotropy and Spin-Locked Superconductivity in K2Cr3As3

International Nuclear Information System (INIS)

Balakirev, Fedor Fedorovich; Kong, T.; Jaime, Marcelo; McDonald, Ross David; Mielke, Charles H.; Gurevich, A.; Canfield, P. C.; Bud'ko, S. L.

2016-01-01

Recently, superconductivity in K 2 Cr 3 As 3 (T c =6.1 K) was discovered. The crystalline lattice contains an array of weakly coupled, double well [(Cr 3 As 3 ) 2- ] ∞ linkages stretched along the c axis, suggesting the possibility of quasi-one-dimensional superconductivity. Moderately anisotropic upper critical field was revealed in single crystals, with very large initial slopes, dH || c2 /dT=12 T/K along the Cr chains and dH perpendicular c2 /dT =7 T/K perpendicular to the chains. Given the ambiguity of conclusions based on the extrapolations of H c2 (T) measured near T c to low temperatures, we performed high-field measurements of H c2 (T) on K 2 Cr 3 As 3 single crystals in pulsed magnetic fields which enabled us to reveal the full anisotropic H c2 (T) curves from T c down to 600 mK.

Dynamic critical phenomena in two-dimensional fully frustrated Coulomb gas model with disorder

International Nuclear Information System (INIS)

Zhang Wei; Luo Mengbo

2008-01-01

The dynamic critical phenomena near depinning transition in two-dimensional fully frustrated square lattice Coulomb gas model with disorders was studied using Monte Carlo technique. The ground state of the model system with disorder σ=0.3 is a disordered state. The dependence of charge current density J on electric field E was investigated at low temperatures. The nonlinear J-E behavior near critical depinning field can be described by a scaling function proposed for three-dimensional flux line system [M.B. Luo, X. Hu, Phys. Rev. Lett. 98 (2007) 267002]. We evaluated critical exponents and found an Arrhenius creep motion for field region E c /2 c . The scaling law of the depinning transition is also obtained from the scaling function

Passive writers and understanding critics. Institution and interpretation in the research field of the anthropology of literature

Directory of Open Access Journals (Sweden)

Aldona Kopkiewicz

2013-01-01

Full Text Available This essay presents a polemic against the anthropology of literature. The author examines the relation between the ethics of interpretation and the discourse of the anthropology of literature as well as cultural studies. She also shows theoretical conditions under which a textual subject appears to be weak and passive and thus becomes just a field in which a researcher can inscribe various cultural identities. In this way a researcher tries to restitute the subject after its poststructural “death”, but he/she might do that only by mediation through social and cultural identities, which he/she actually examines. On the practical level this entanglement causes a situation in which writers and artists create works that fulfill institutional expectations. It would be therefore necessary to establish to what extent an anthropological approach towards a text enables us to invent new models of subjectivity. Without this it would be difficult to consider literary/cultural studies to be a truly critical discipline based on independent, yet collaborative reflection to be found in theoretical and artistic texts alike.

A Study of Critical Flowrate in the Integral Effect Test Facilities

International Nuclear Information System (INIS)

Kim, Yeongsik; Ryu, Sunguk; Cho, Seok; Yi, Sungjae; Park, Hyunsik

2014-01-01

In earlier studies, most of the information available in the literature was either for a saturated two-phase flow or a sub-cooled water flow at medium pressure conditions, e. g., up to about 7.0 MPa. The choking is regarded as a condition of maximum possible discharge through a given orifice and/or nozzle exit area. A critical flow rate can be achieved at a choking under the given thermo-hydraulic conditions. The critical flow phenomena were studied extensively in both single-phase and two-phase systems because of its importance in the LOCA analyses of light water reactors and in the design of other engineering areas. Park suggested a modified correlation for predicting the critical flow for sub-cooled water through a nozzle. Recently, Park et al. performed an experimental study on a two-phase critical flow with a noncondensable gas at high pressure conditions. Various experiments of critical flow using sub-cooled water were performed for a modeling of break simulators in thermohydraulic integral effect test facilities for light water reactors, e. g., an advanced power reactor 1400MWe (APR1400) and a system-integrated modular advanced reactor (SMART). For the design of break simulators of SBLOCA scenarios, the aspect ratio (L/D) is considered to be a key parameter to determine the shape of a break simulator. In this paper, an investigation of critical flow phenomena was performed especially on break simulators for LOCA scenarios in the integral effect test facilities of KAERI, such as ATLAS and FESTA. In this study, various studies on the critical flow models for sub-cooled and/or saturated water were reviewed. For a comparison among the models for the selected test data, discussions of the comparisons on the effect of the diameters, predictions of critical flow models, and break simulators for SBLOCA in the integral effect test facilities were presented

A Study of Critical Flowrate in the Integral Effect Test Facilities

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeongsik; Ryu, Sunguk; Cho, Seok; Yi, Sungjae; Park, Hyunsik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

In earlier studies, most of the information available in the literature was either for a saturated two-phase flow or a sub-cooled water flow at medium pressure conditions, e. g., up to about 7.0 MPa. The choking is regarded as a condition of maximum possible discharge through a given orifice and/or nozzle exit area. A critical flow rate can be achieved at a choking under the given thermo-hydraulic conditions. The critical flow phenomena were studied extensively in both single-phase and two-phase systems because of its importance in the LOCA analyses of light water reactors and in the design of other engineering areas. Park suggested a modified correlation for predicting the critical flow for sub-cooled water through a nozzle. Recently, Park et al. performed an experimental study on a two-phase critical flow with a noncondensable gas at high pressure conditions. Various experiments of critical flow using sub-cooled water were performed for a modeling of break simulators in thermohydraulic integral effect test facilities for light water reactors, e. g., an advanced power reactor 1400MWe (APR1400) and a system-integrated modular advanced reactor (SMART). For the design of break simulators of SBLOCA scenarios, the aspect ratio (L/D) is considered to be a key parameter to determine the shape of a break simulator. In this paper, an investigation of critical flow phenomena was performed especially on break simulators for LOCA scenarios in the integral effect test facilities of KAERI, such as ATLAS and FESTA. In this study, various studies on the critical flow models for sub-cooled and/or saturated water were reviewed. For a comparison among the models for the selected test data, discussions of the comparisons on the effect of the diameters, predictions of critical flow models, and break simulators for SBLOCA in the integral effect test facilities were presented.

Dimensional Crossover and Its Interplay with In-Plane Anisotropy of Upper Critical Field in β-(BDA-TTP)2SbF6

Science.gov (United States)

Yasuzuka, Syuma; Koga, Hiroaki; Yamamura, Yasuhisa; Saito, Kazuya; Uji, Shinya; Terashima, Taichi; Akutsu, Hiroki; Yamada, Jun-ichi

2017-08-01

Resistance measurements have been performed to investigate the dimensionality and the in-plane anisotropy of the upper critical field (Hc2) for β-(BDA-TTP)2SbF6 in fields H up to 15 T and at temperatures T from 1.5 to 7.5 K, where BDA-TTP stands for 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene. The upper critical fields parallel and perpendicular to the conduction layer are determined and dimensional crossover from anisotropic three-dimensional behavior to two-dimensional behavior is found at around 6 K. When the direction of H is varied within the conducting layer at 6.0 K, Hc2 shows twofold symmetry: Hc2 along the minimum Fermi wave vector (maximum Fermi velocity) is larger than that along the maximum Fermi wave vector (minimum Fermi velocity). The normal-state magnetoresistance has twofold symmetry similar to Hc2 and shows a maximum when the magnetic field is nearly parallel to the maximum Fermi wave vector. This tendency is consistent with the Fermi surface anisotropy. At 3.5 K, we found clear fourfold symmetry of Hc2 despite the fact that the normal-state magnetoresistance shows twofold symmetry arising from the Fermi surface anisotropy. The origin of the fourfold symmetry of Hc2 is discussed in terms of the superconducting gap structure in β-(BDA-TTP)2SbF6.

Dimensional crossover and its interplay with in-plane anisotropy of upper critical field in β-(BDA-TTP)_2SbF_6

International Nuclear Information System (INIS)

Yasuzuka, Syuma; Koga, Hiroaki; Yamamura, Yasuhisa; Saito, Kazuya; Uji, Shinya; Terashima, Taichi; Akutsu, Hiroki; Yamada, Jun-ichi

2017-01-01

Resistance measurements have been performed to investigate the dimensionality and the in-plane anisotropy of the upper critical field (H_c_2) for β-(BDA-TTP)_2SbF_6 in fields H up to 15 T and at temperatures T from 1.5 to 7.5 K, where BDA-TTP stands for 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene. The upper critical fields parallel and perpendicular to the conduction layer are determined and dimensional crossover from anisotropic three-dimensional behavior to two-dimensional behavior is found at around 6 K. When the direction of H is varied within the conducting layer at 6.0 K, H_c_2 shows twofold symmetry: H_c_2 along the minimum Fermi wave vector (maximum Fermi velocity) is larger than that along the maximum Fermi wave vector (minimum Fermi velocity). The normal-state magnetoresistance has twofold symmetry similar to H_c_2 and shows a maximum when the magnetic field is nearly parallel to the maximum Fermi wave vector. This tendency is consistent with the Fermi surface anisotropy. At 3.5 K, we found clear fourfold symmetry of H_c_2 despite the fact that the normal-state magnetoresistance shows twofold symmetry arising from the Fermi surface anisotropy. The origin of the fourfold symmetry of H_c_2 is discussed in terms of the superconducting gap structure in β-(BDA-TTP)_2SbF_6. (author)

The french criticality handbook

International Nuclear Information System (INIS)

Maubert, L.; Puit, J.C.

1987-01-01

The french criticality handbook, published in 1978 by the ''Commissariat a l'Energie Atomique'', is presented with the main targets aimed by the writer and the main choices taken relating to fissile mediums, reflection conditions, dilution curves. The validation of the critical values is presented as one of the most important aspects of this handbook which is mainly intended, in the mind of the author, to specialists well advertised in the field of criticality. The complements which have been introduced since 1978 and those which are foreseen in a near future are also detailed. (author)

Volume pinning force and upper critical field of irradiated Nb3Sn

International Nuclear Information System (INIS)

Maier, P.; Seibt, E.

1981-01-01

Irradiation by neutrons and ions in A15 superconductors (Nb 3 Sn, V 3 Ga) exerts a stronger influence on the pinning behavior than in nonordered alloys (NbTi). In this work it is shown for deuteron irradiated Nb 3 /Sn wires prepared by the bronze process that the dose curve of the volume pinning force P/sub V/ can be conveniently described by a sum of two terms, due to the grain boundary pinning and to the radiation pinning, respectively. After deduction of the contribution by the radiation-induced pinning centers, good agreement is obtained between the measured P/sub V/ values and those calculated using the upper critical field B/sub c/2 and the transition temperature T/sub c/ on the basis of the irradiation fluence. The use of a theoretical relationship between B/sub c/2 and T/sub c/ is supported by measured values. Application to multifilamentary superconductors with high current carrying capabilities simplifies the calculation of P/sub V/, since the radiation induced volume pinning force can be neglected

Differences between two definitions of the critical current of HTS coils

International Nuclear Information System (INIS)

Pitel, Jozef

2013-01-01

Definition of the critical current of a coil made of anisotropic high temperature superconducting conductor is rather complicated and ambiguous, since the magnetic field generated across the winding can differ considerably in relation to both its magnitude and orientation. Two definitions of the critical current of such coils are discussed. The first definition, very often used in calculations to analyze the current carrying capacity, electric field and power dissipation of individual turns, represents an operating current at which an electric field of 1 μV cm −1 appears on one turn. The second definition represents an integral approach, and is used in experiments. This definition introduces the critical current of the coil as an operating current at which an average electric field E s , usually 0.1 μV cm −1 , appears on coil terminals. As an example, the distribution of the critical current and electric field of individual turns in the winding of a BSCCO model coil was analyzed. Critical currents of the coil as a function of an external magnetic field parallel with the coil axis were calculated according to both definitions. The results show that the first definition, which characterizes the winding at the local level, is suitable for HTS coils either operating in self-field or in a low external field, because the differences between the critical currents and n-indices of individual turns are considerable. The second criterion is suitable for the HTS coils operating in high fields, i.e. like high field insert coils. The self-field of a high field insert coil is negligible if the external field is high. As a result, the critical currents of all turns are almost identical, and the anisotropy in I c (B) characteristic plays practically no role. Rather unexpected behavior of the voltage–current characteristic of the model coil is predicted if an external field is applied. (paper)

Static critical phenomena in Co-Ni-Ga ferromagnetic shape memory alloy

International Nuclear Information System (INIS)

Sethi, Brahmananda; Sarma, S.; Srinivasan, A.; Santra, S. B.

2014-01-01

Ferromagnetic shape memory alloys are smart materials because they exhibit temperature driven shape memory effect and magnetic field induced strain. Thus two types of energy, i.e. thermal and magnetic, are used to control their shape memory behaviour. Study of critical phenomenon in such materials has received increased experimental and theoretical attention for better understanding of the magnetic phase transition behavior as well as further development of ferromagnetic shape memory materials. In the present study we report the preparation and characterization of bulk Co 45 Ni 25 Ga 30 alloy, prepared by a sequence of arc melting technique followed by homogenization at 1150 °C for 24 hours and ice-water quenching. Structural and magnetic properties of the alloys were studied by means of X-ray diffraction and vibrating sample magnetometer in an applied field range of ±18 kOe equipped with a high temperature oven. We have determined the critical temperature T C (∼375.5 K) and the critical exponents viz; β=0.40, γ=1.68 and δ=5.2. Asymptotic critical exponents β, γ, and δ obey Widom scaling relation, γ+β=βδ, and the magnetization data satisfy the scaling equation of state for second-order phase transition in the asymptotic critical region

Study of two-phase critical flows through small breaches

International Nuclear Information System (INIS)

Chalant, Jean Marc; Willocx, Marc

1981-06-01

The first part of this academic document reports experimental works performed for the design and realisation of an installation (DALIDA) aimed at the study of critical flow rates through a hole. As this experimental study had to be given up for practical reasons, the authors focused on the theoretical study of this phenomenon. Based on a model proposed by Lackme for critical flows in long tubes, the authors developed a model which could be applied to the case of a tube ended by a hole. Numerical results have been obtained which are still to be experimentally confirmed [fr

R and D study on on-line criticality surveillance system (V)

International Nuclear Information System (INIS)

Yamada, Sumasu

2001-02-01

In view of necessity and importance of criticality surveillance systems for ensuring the safety of nuclear fuel manufacturing and reprocessing plants, 5-year basic studies and 4 year R and D studies on an on-line criticality surveillance system were carried out since 1991. This report is a summary of these series of studies. Noticing that the signal from a neutron detector is random in principle, these series of studies aimed to accumulate knowledge for developing an inexpensive criticality surveillance system with quick response based on the Auto-Regressive Moving Average (ARMA) model identification algorithm. During five-year basic studies on criticality surveillance system since 1991, we obtained knowledge required for developing a criticality surveillance system based on the ARMA model identification algorithm through 1) studies on recursive ARMA model identification algorithms most appropriate for estimating subcriticality form time series data under a steady state condition, 2) studies on pre-processing of signal from neutron detectors, 3) developing a new recursive ARMA model identification algorithm with small time delay to estimate time-dependent subcriticality, 4) proposing a basic concept for the elements required for an on-line criticality surveillance system, and 5) numerical analysis of data from the DCA experiments. During next four-year R and D studies on a criticality surveillance system since 1996, we 1) proposed modules required for a no-line criticality surveillance system, 2) revealed effectiveness of a adaptive digital filter (ADF) algorithm, as an important redundancy to the recursive ARMA model identification algorithm to be used in the signal processing module through numerical analysis of real data, 3) proposed a module of the Feynman-α method over γ ray signal and a fast signal processing module for γ ray signal, 4) developed a line-noise removal filter(Notch filter) and revealed its effectiveness for the DCA data corrupted with power

Determination of critical exponents of inhomogeneous Gd films

Energy Technology Data Exchange (ETDEWEB)

Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Salazar, N.A. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Hovorka, O.; Idigoras, O.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain)

2012-08-15

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T{sub AN}=200, 400, and 500 Degree-Sign C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T{sub C} was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.

Determination of critical exponents of inhomogeneous Gd films

International Nuclear Information System (INIS)

Rosales-Rivera, A.; Salazar, N.A.; Hovorka, O.; Idigoras, O.; Berger, A.

2012-01-01

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T AN =200, 400, and 500 °C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T C was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.

The factors influencing burnout and job satisfaction among critical care nurses: a study of Saudi critical care nurses.

Science.gov (United States)

Alharbi, Jalal; Wilson, Rhonda; Woods, Cindy; Usher, Kim

2016-09-01

The aim of the study was to explore the prevalence of burnout and job satisfaction among Saudi national critical care nurses. Burnout is caused by a number of factors, including personal, organisational and professional issues. Previous literature reports a strong relationship between burnout and job satisfaction among critical care nurses. Little is known about this phenomenon among Saudi national critical care nurses. A convenience sample of 150 Saudi national critical care nurses from three hospitals in Hail, Saudi Arabia were included in a cross-sectional survey. Saudi national critical care registered nurses reported moderate to high levels of burnout in the areas of emotional exhaustion and depersonalisation. Participants also reported a feeling of ambivalence and dissatisfaction with their jobs but were satisfied with the nature of their work. Saudi national critical care nurses experience moderate to high levels of burnout and low levels of job satisfaction. Burnout is a predictor of job satisfaction for Saudi national critical care nurses. These results provide clear evidence of the need for nurse managers and policy makers to devise strategies to help nurses better cope with a stressful work environment, thereby also improving job satisfaction among Saudi national critical care nurses. © 2016 John Wiley & Sons Ltd.

Quantum criticality of one-dimensional multicomponent Fermi gas with strongly attractive interaction

International Nuclear Information System (INIS)

He, Peng; Jiang, Yuzhu; Guan, Xiwen; He, Jinyu

2015-01-01

Quantum criticality of strongly attractive Fermi gas with SU(3) symmetry in one dimension is studied via the thermodynamic Bethe ansatz (TBA) equations. The phase transitions driven by the chemical potential μ, effective magnetic field H 1 , H 2 (chemical potential biases) are analyzed at the quantum criticality. The phase diagram and critical fields are analytically determined by the TBA equations in the zero temperature limit. High accurate equations of state, scaling functions are also obtained analytically for the strong interacting gases. The dynamic exponent z=2 and correlation length exponent ν=1/2 read off the universal scaling form. It turns out that the quantum criticality of the three-component gases involves a sudden change of density of states of one cluster state, two or three cluster states. In general, this method can be adapted to deal with the quantum criticality of multicomponent Fermi gases with SU(N) symmetry. (paper)

Situational awareness and information flow in prehospital emergency medical care from the perspective of paramedic field supervisors: a scenario-based study.

Science.gov (United States)

Norri-Sederholm, Teija; Paakkonen, Heikki; Kurola, Jouni; Saranto, Kaija

2015-01-16

In prehospital emergency medical services, one of the key factors in the successful delivery of appropriate care is the efficient management and supervision of the area's emergency medical services units. Paramedic field supervisors have an important role in this task. One of the key factors in the daily work of paramedic field supervisors is ensuring that they have enough of the right type of information when co-operating with other authorities and making decisions. However, a gap in information sharing still exists especially due to information overload. The aim of this study was to find out what type of critical information paramedic field supervisors need during multi-authority missions in order to manage their emergency medical services area successfully. The study also investigated both the flow of information, and interactions with the paramedic field supervisors and the differences that occur depending on the incident type. Ten paramedic field supervisors from four Finnish rescue departments participated in the study in January-March 2012. The data were collected using semi-structured interviews based on three progressive real-life scenarios and a questionnaire. Data were analysed using deductive content analysis. Data management and analysis were performed using Atlas.ti 7 software. Five critical information categories were formulated: Incident data, Mission status, Area status, Safety at work, and Tactics. Each category's importance varied depending on the incident and on whether it was about information needed or information delivered by the paramedic field supervisors. The main communication equipment used to receive information was the authority radio network (TETRA). However, when delivering information, mobile phones and TETRA were of equal importance. Paramedic field supervisors needed more information relating to area status. Paramedic field supervisors communicate actively with EMS units and other authorities such as Emergency Medical Dispatch

Critical properties of symmetric nanoscale metal-ferroelectric-metal capacitors

International Nuclear Information System (INIS)

Zheng Yue; Cai, M.Q.; Woo, C.H.

2010-01-01

The size, surface and interface effects on the magnitude and stability of spontaneous polarization in a symmetric nanoscale ferroelectric capacitor were studied by analyzing its evolutionary trajectory based on a thermodynamic model. Analytic expressions of the Curie temperature, spontaneous polarization, critical thickness and the Curie-Weiss relation were derived, taking into account the effects of the depolarization field, built-in electric field, interfaces and surfaces. Our results show that the critical properties are not only functions of the ambient temperature, misfit strain and electromechanical boundary conditions, but also depend on the characteristics of electrodes, surfaces and interfaces, through the incomplete charge compensation, near-surface variation of polarization and work function steps of ferroelectric-electrode interfaces, which are adjustable.

Critical Phenomena in Higher Curvature Charged AdS Black Holes

Directory of Open Access Journals (Sweden)

Arindam Lala

2013-01-01

Full Text Available In this paper, we have studied the critical phenomena in higher curvature charged AdS black holes. We have considered Lovelock-Born-Infeld-AdS black hole as an example. The thermodynamics of the black hole have been studied which reveals the onset of a higher-order phase transition in the black hole in the canonical ensemble (fixed charge ensemble framework. We have analytically derived the critical exponents associated with these thermodynamic quantities. We find that our results fit well with the thermodynamic scaling laws and consistent with the mean field theory approximation. The suggestive values of the other two critical exponents associated with the correlation function and correlation length on the critical surface have been derived.

Critical Fluctuations in Spatial Complex Networks

Science.gov (United States)

Bradde, Serena; Caccioli, Fabio; Dall'Asta, Luca; Bianconi, Ginestra

2010-05-01

An anomalous mean-field solution is known to capture the nontrivial phase diagram of the Ising model in annealed complex networks. Nevertheless, the critical fluctuations in random complex networks remain mean field. Here we show that a breakdown of this scenario can be obtained when complex networks are embedded in geometrical spaces. Through the analysis of the Ising model on annealed spatial networks, we reveal, in particular, the spectral properties of networks responsible for critical fluctuations and we generalize the Ginsburg criterion to complex topologies.

[Introduction to critical reading of articles: study design and biases].

Science.gov (United States)

García Villar, C

2015-01-01

The critical evaluation of an article enables professionals to make good use of the new information and therefore has direct repercussions for the benefit of our patients. Before undertaking a detailed critical reading of the chosen article, we need to consider whether the study used the most appropriate design for the question it aimed to answer (i.e., whether the level of evidence is adequate). To do this, we need to know how to classify studies in function of their design (descriptive or analytical; prospective or retrospective; cross-sectional or longitudinal) as well as their correlation with the levels of evidence. In critical reading it is also important to know the main systematic errors or biases that can affect a study. Biases can appear in any phase of a study; they can affect the sample, the development of the study, or the measurement of the results. Copyright © 2014 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

Patient outcomes after critical illness: a systematic review of qualitative studies following hospital discharge.

Science.gov (United States)

Hashem, Mohamed D; Nallagangula, Aparna; Nalamalapu, Swaroopa; Nunna, Krishidhar; Nausran, Utkarsh; Robinson, Karen A; Dinglas, Victor D; Needham, Dale M; Eakin, Michelle N

2016-10-26

There is growing interest in patient outcomes following critical illness, with an increasing number and different types of studies conducted, and a need for synthesis of existing findings to help inform the field. For this purpose we conducted a systematic review of qualitative studies evaluating patient outcomes after hospital discharge for survivors of critical illness. We searched the PubMed, EMBASE, CINAHL, PsycINFO, and CENTRAL databases from inception to June 2015. Studies were eligible for inclusion if the study population was >50 % adults discharged from the ICU, with qualitative evaluation of patient outcomes. Studies were excluded if they focused on specific ICU patient populations or specialty ICUs. Citations were screened in duplicate, and two reviewers extracted data sequentially for each eligible article. Themes related to patient outcome domains were coded and categorized based on the main domains of the Patient Reported Outcomes Measurement Information System (PROMIS) framework. A total of 2735 citations were screened, and 22 full-text articles were eligible, with year of publication ranging from 1995 to 2015. All of the qualitative themes were extracted from eligible studies and then categorized using PROMIS descriptors: satisfaction with life (16 studies), including positive outlook, acceptance, gratitude, independence, boredom, loneliness, and wishing they had not lived; mental health (15 articles), including symptoms of post-traumatic stress disorder, anxiety, depression, and irritability/anger; physical health (14 articles), including mobility, activities of daily living, fatigue, appetite, sensory changes, muscle weakness, and sleep disturbances; social health (seven articles), including changes in friends/family relationships; and ability to participate in social roles and activities (six articles), including hobbies and disability. ICU survivors may experience positive emotions and life satisfaction; however, a wide range of mental

Parametric study of the criticality of natural reactors

International Nuclear Information System (INIS)

Naudet, R.

1978-01-01

Conditions for the criticality of natural reactors are investigated from a general point of view; a parametric study is presented, which expresses the possibility of chain reactions as functions of five parameters: the age of the deposit, the ore's uranium content, the volume of high-grade ore, the neutron capture of the vein of ore and the amount of water associated with the uranium. It is demonstrated that although criticality could theoretically be attained for ages that are not in excess of 1000 to 1200 MA, conditions would have to be exceptionally favorable for it since the deposits are clearly much younger than those at Oklo. The study offers a much better appreciation of the probability for discovery of other natural fissionable reactors

An all-field-range description of the critical current density in superconducting YBCO films

International Nuclear Information System (INIS)

Golovchanskiy, I A; Pan, A V; Shcherbakova, O V; Fedoseev, S A; Dou, S X

2011-01-01

A new critical current density (J c ) model for high-quality YBCO (YBa 2 Cu 3 O 7 ) thin films has been proposed, combining thermally activated flux creep with a vortex pinning potential for columnar defects. The pinning for thermally activated vortices has been described as strong pinning on chains of individual edge dislocations that form low-angle domain boundaries in high-quality YBCO thin films. The model yields an adequate description of the J c behaviour over the whole applied field range, as verified by direct measurements of J c in YBCO thin films grown by pulsed-laser deposition. It also indicates that the effective pinning landscape changes under the influence of the external conditions. Remarkably, the pinning potential obtained from the model is consistent with the values obtained for columnar defects, which confirms the validity of the overall approach.

Super critical water reactors

International Nuclear Information System (INIS)

Dumaz, P.; Antoni, O; Arnoux, P.; Bergeron, A; Renault, C.; Rimpault, G.

2005-01-01

Water is used as a calori-porter and moderator in the most major nuclear centers which are actually in function. In the pressurized water reactor (PWR) and boiling water reactor (BWR), water is maintained under critical point of water (21 bar, 374 Centigrade) which limits the efficiency of thermodynamic cycle of energy conversion (yield gain of about 33%) Crossing the critical point, one can then use s upercritical water , the obtained pressure and temperature allow a significant yield gains. In addition, the supercritical water offers important properties. Particularly there is no more possible coexistence between vapor and liquid. Therefore, we don't have more boiling problem, one of the phenomena which limits the specific power of PWR and BWR. Since 1950s, the reactor of supercritical water was the subject of studies more or less detailed but neglected. From the early 1990s, this type of conception benefits of some additional interests. Therefore, in the international term G eneration IV , the supercritical water reactors had been considered as one of the big options for study as Generation IV reactors. In the CEA, an active city has engaged from 1930 with the participation to a European program: The HPWR (High Performance Light Water Reactor). In this contest, the R and D studies are focused on the fields of neutrons, thermodynamic and materials. The CEA intends to pursue a limited effort of R and D in this field, in the framework of international cooperation, preferring the study of versions of rapid spectrum. (author)

Critical behavior of the dielectric constant in asymmetric fluids.

Science.gov (United States)

Bertrand, C E; Sengers, J V; Anisimov, M A

2011-12-08

By applying a thermodynamic theory that incorporates the concept of complete scaling, we derive the asymptotic temperature dependence of the critical behavior of the dielectric constant above the critical temperature along the critical isochore and below the critical temperature along the coexistence curve. The amplitudes of the singular terms in the temperature expansions are related to the changes of the critical temperature and the critical chemical potential upon the introduction of an electric field. The results of the thermodynamic theory are then compared with the critical behavior implied by the classical Clausius-Mossotti approximation. The Clausius-Mossotti approximation fails to account for any singular temperature dependence of the dielectric constant above the critical temperature. Below the critical temperature it produces an apparent asymmetric critical behavior with singular terms similar to those implied by the thermodynamic theory, but with significantly different coefficients. We conclude that the Clausius-Mossotti approximation only can account for the observed asymptotic critical behavior of the dielectric constant when the dependence of the critical temperature on the electric field is negligibly small. © 2011 American Chemical Society

T-S criticality of black holes with power Maxwell invariant source

Science.gov (United States)

Lin, Ze-Tao; Li, Gu-Qiang; Long, Kun; He, Fang; Mo, Jie-Xiong

2017-09-01

In this paper, we show that black holes with PMI source exhibit the T-S criticality and derive the relevant critical physical quantities analytically. The values of critical quantities for the case s≠1 vary from those for the case s=1, showing the effect of PMI field on the critical phenomena of black holes. When qPMI field does not affect the Maxwell equal area law.

Dynamics of quantum discord in a quantum critical environment

International Nuclear Information System (INIS)

Xi Zhengjun; Li Yongming; Lu Xiaoming; Sun Zhe

2011-01-01

We study the dynamics of quantum discord (QD) of two qubits independently coupled to an Ising spin chain in a transverse field, which exhibits a quantum phase transition. For this model, we drive the corresponding Kraus operators, obtain the analytic results of QD and compare the dynamics of QD with the dynamics of relative entropy of entanglement nearby the critical point. It is shown that the impact of the quantum criticality environment on QD can be concentrated in a very narrow region nearby the critical point, so it supplies an efficient way to detect the critical points. In the vicinity of the critical point, the evolution of QD is shown to be more complicated than that of entanglement. Furthermore, we find that separable states can also be used to reflect the quantum criticality of the environment.

Critical Management Studies: Some Reflections

Directory of Open Access Journals (Sweden)

Rafael Alcadipani

2008-01-01

Full Text Available This paper seeks to challenge some assumptions associated with Critical Management Studies (CMS. This is done based on insights originating from the Actor-Network Theory (ANT, an approach that can be considered as an empirical form of post-structuralism and that has gained prominence in social sciences. Fundamentally, this paper broadly reviews some key CMS ideas associated with this perspective ontology to argue that what CMS usually tends to take as explanation is exactly what has to be explained. Moreover, it discusses CMS’ problematic view of objects and its tendency to neglect how existence is kept and maintained.

Analytical study of a reversed-field pinch with rectangular cross section

International Nuclear Information System (INIS)

Zhang Peng

1990-01-01

An analyic solution of the force-free equation for a toroidal configuration of rectangular cross section is presented. It is shown that the critical value of contraction ratio for the appearance of a reversed field as well as of the ohmic current increases as the elongation of the cross section increases

Improvement of critical currents in Bi-2223 bulk superconductors

International Nuclear Information System (INIS)

Eujen, R.; Brauer, D.J.; Huedepohl, J.

1991-01-01

Potential applications of the high-Tc superconductors for energy transport or high-field magnets require high critical current densities. A limiting factor in polycrystalline oxidic materials is the quality of the grain boundaries. Weak links have been made responsible for the steep decrease in the critical current density j c upon application of even weak magnetic fields of YBa CuO whereas flux creep seems to dominate the obtainable j c values for the Bi-Sr-Ca-Cu-O system (BSCCO) at 77 K. In the lead containing material (BPSCCO) the formation of a porous microstructure is enhanced by the platelike shape of the crystals. Special techniques such as powder-in-tube, hot isostatic pressing, zone melting or application of fluxes have been used in order to improve the grain contacts. A positive influence of fluxes on j c , e.g. by addition of Ca 2 CuO 3 or Ag 2 O, has been reported. In this study we have investigated the influence of various compositions and conditions on the formation of the BSCCO-2223 phase (T c ca. 107 K), the critical current density j c , and the magnet field dependence of the a.c. susceptibility. (orig.)

The Lathrop Wells volcanic center: Status of field and geochronology studies

International Nuclear Information System (INIS)

Crowe, B.; Morley, R.; Wells, S.; Geissman, J.; McDonald, E.; McFadden, L.; Perry, F.; Murrell, M.; Poths, J.; Forman, S.

1993-01-01

The Lathrop Wells volcanic center is located 20 km south of the potential Yucca Mountain site, at the south end of the Yucca Mountain range. It has long been recognized as the youngest basalt center in the region. However, determination of the age and eruptive history of the center has proven problematic. The purpose of this paper is to describe the status of field and geochronology studies of the Lathrop Wells center. Our perspective is that it is critical to assess all possible methods for obtaining cross-checking data to resolve chronology and field problems. It is equally important to consider application of the range of chronology methods available in Quaternary geologic research. Such an approach seeks to increase the confidence in data interpretations through obtaining convergence among separate isotopic, radiogenic, and age-correlated methods. Finally, the assumptions, strengths, and weaknesses of each dating method need to be carefully described to facilitate an impartial evaluation of results

The critical interface

DEFF Research Database (Denmark)

Pold, Søren

2005-01-01

In this paper, I argue that aesthetics might serve the role of critical reflection on representation within the field of computing, and I demonstrate through three analytic examples from computer art how this might look like and what the contribution might be....

Critical Studies, the Liberal Arts, and Journalism Education.

Science.gov (United States)

Parisi, Peter

1992-01-01

Discusses the relationship between journalism education and the liberal arts. Contends that critical, cultural, or qualitative studies provide a powerful focus for linking journalism education more firmly to the liberal arts. (SR)

The Biomantle-Critical Zone Model

Science.gov (United States)

Johnson, D. L.; Lin, H.

2006-12-01

It is a fact that established fields, like geomorphology, soil science, and pedology, which treat near surface and surface processes, are undergoing conceptual changes. Disciplinary self examinations are rife. New practitioners are joining these fields, bringing novel and interdisciplinary ideas. Such new names as "Earth's critical zone," "near surface geophysics," and "weathering engine" are being coined for research groups. Their agendas reflect an effort to integrate and reenergize established fields and break new ground. The new discipline "hydropedology" integrates soil science with hydrologic principles, and recent biodynamic investigations have spawned "biomantle" concepts and principles. One force behind these sea shifts may be retrospectives whereby disciplines periodically re-invent themselves to meet new challenges. Such retrospectives may be manifest in the recent Science issue on "Soils, The Final Frontier" (11 June, 2004), and in recent National Research Council reports that have set challenges to science for the next three decades (Basic Research Opportunities in Earth Science, and Grand Challenges for the Environmental Sciences, both published in 2001). In keeping with such changes, we advocate the integration of biomantle and critical zone concepts into a general model of Earth's soil. (The scope of the model automatically includes the domain of hydropedology.) Our justification is that the integration makes for a more appealing holistic, and realistic, model for the domain of Earth's soil at any scale. The focus is on the biodynamics of the biomantle and water flow within the critical zone. In this general model the biomantle is the epidermis of the critical zone, which extends to the base of the aquifer. We define soil as the outer layer of landforms on planets and similar bodies altered by biological, chemical, and/or physical agents. Because Earth is the only planet with biological agents, as far as we know, it is the only one that has all

Four Tools for Critical Inquiry in History, Social Studies, and Civic Education

OpenAIRE

Bermudez, Angela

2015-01-01

The promotion of critical thinking is an important but elusive goal in history, social studies, and civic education. Teachers often struggle to translate general definitions of critical thinking into specific pedagogical tools to plan learning activities and to observe and interpret student work in these subjects. They also struggle to distinguish between "teaching critical content" and "teaching students to think critically." In this paper, I draw upon scholarship on critical thinking, histo...

ILearning and EHomeStudy: Multimedia Training and Assessments for Field Survey Staff

Directory of Open Access Journals (Sweden)

Charles Loftis

2008-04-01

Full Text Available Survey data collection projects strive to collect high quality data from survey respondents. The quality of the data collected is greatly dependent upon the effectiveness of field interviewers (FIs to conduct inperson screenings and interviews. Training FIs and subsequently assessing their knowledge of project protocol, methods and interviewing techniques is critical to the overall success of any data collection effort. For large surveys, as the number of FIs increase, the cost of inperson training can become prohibitively large. As a cost effective solution to increase the quality of the field data, we developed a suite of web and media based training and assessment tools called iLearning and eHomeStudy for training field staff. Besides saving the project costs associated with inperson training, we are also able to provide refresher trainings throughout the year. This application also enables FIs to view standardized training courses at their convenience and at their own pace. This paper describes the technical details, key features and benefits of this application suite, and also it includes some details on user satisfaction and future directions.

Automated Critical Peak Pricing Field Tests: Program Descriptionand Results

Energy Technology Data Exchange (ETDEWEB)

Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila; Xu, Peng

2006-04-06

California utilities have been exploring the use of critical peak prices (CPP) to help reduce needle peaks in customer end-use loads. CPP is a form of price-responsive demand response (DR). Recent experience has shown that customers have limited knowledge of how to operate their facilities in order to reduce their electricity costs under CPP (Quantum 2004). While the lack of knowledge about how to develop and implement DR control strategies is a barrier to participation in DR programs like CPP, another barrier is the lack of automation of DR systems. During 2003 and 2004, the PIER Demand Response Research Center (DRRC) conducted a series of tests of fully automated electric demand response (Auto-DR) at 18 facilities. Overall, the average of the site-specific average coincident demand reductions was 8% from a variety of building types and facilities. Many electricity customers have suggested that automation will help them institutionalize their electric demand savings and improve their overall response and DR repeatability. This report focuses on and discusses the specific results of the Automated Critical Peak Pricing (Auto-CPP, a specific type of Auto-DR) tests that took place during 2005, which build on the automated demand response (Auto-DR) research conducted through PIER and the DRRC in 2003 and 2004. The long-term goal of this project is to understand the technical opportunities of automating demand response and to remove technical and market impediments to large-scale implementation of automated demand response (Auto-DR) in buildings and industry. A second goal of this research is to understand and identify best practices for DR strategies and opportunities. The specific objectives of the Automated Critical Peak Pricing test were as follows: (1) Demonstrate how an automated notification system for critical peak pricing can be used in large commercial facilities for demand response (DR). (2) Evaluate effectiveness of such a system. (3) Determine how customers

The critical properties of magnetic films

International Nuclear Information System (INIS)

Saber, M.; Ainane, A.; Essaoudi, I.; Miguel, J.J. de

2010-01-01

Within the framework of the transverse spin-1/2 Ising model and by using the effective field theory with a probability distribution technique that accounts for the self spin correlations, we have studied the critical properties of an L-layer film of simple cubic symmetry in which the exchanges strength are assumed to be different from the bulk values in N S surface layers. We derive and illustrate the expressions for the phase diagrams, order parameter profiles and susceptibility. In such films, the critical temperature can shift to either lower or higher temperature compared with the corresponding bulk value. We calculate also some magnetic properties of the film, such as the layer magnetizations, their averages and their profiles and the longitudinal susceptibility of the film. The film longitudinal susceptibility still diverges at the film critical temperature as does the bulk longitudinal susceptibility.

Quantifying cannabis: A field study of marijuana quantity estimation.

Science.gov (United States)

Prince, Mark A; Conner, Bradley T; Pearson, Matthew R

2018-05-17

The assessment of marijuana use quantity poses unique challenges. These challenges have limited research efforts on quantity assessments. However, quantity estimates are critical to detecting associations between marijuana use and outcomes. We examined accuracy of marijuana users' estimations of quantities of marijuana they prepared to ingest and predictors of both how much was prepared for a single dose and the degree of (in)accuracy of participants' estimates. We recruited a sample of 128 regular-to-heavy marijuana users for a field study wherein they prepared and estimated quantities of marijuana flower in a joint or a bowl as well as marijuana concentrate using a dab tool. The vast majority of participants overestimated the quantity of marijuana that they used in their preparations. We failed to find robust predictors of estimation accuracy. Self-reported quantity estimates are inaccurate, which has implications for studying the link between quantity and marijuana use outcomes. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Unconventional Quantum Critical Points

OpenAIRE

Xu, Cenke

2012-01-01

In this paper we review the theory of unconventional quantum critical points that are beyond the Landau's paradigm. Three types of unconventional quantum critical points will be discussed: (1). The transition between topological order and semiclassical spin ordered phase; (2). The transition between topological order and valence bond solid phase; (3). The direct second order transition between different competing orders. We focus on the field theory and universality class of these unconventio...

Deconfined quantum criticality of the O(3) nonlinear σ model in two spatial dimensions: A renormalization-group study

International Nuclear Information System (INIS)

Kim, Ki-Seok

2005-01-01

We investigate the quantum phase transition of the O(3) nonlinear σ model without Berry phase in two spatial dimensions. Utilizing the CP 1 representation of the nonlinear σ model, we obtain an effective action in terms of bosonic spinons interacting via compact U(1) gauge fields. Based on the effective field theory, we find that the bosonic spinons are deconfined to emerge at the quantum critical point of the nonlinear σ model. It is emphasized that the deconfinement of spinons is realized in the absence of Berry phase. This is in contrast to the previous study of Senthil et al. [Science 303, 1490 (2004)], where the Berry phase plays a crucial role, resulting in the deconfinement of spinons. It is the reason why the deconfinement is obtained even in the absence of the Berry phase effect that the quantum critical point is described by the XY ('neutral') fixed point, not the IXY ('charged') fixed point. The IXY fixed point is shown to be unstable against instanton excitations and the instanton excitations are proliferated. At the IXY fixed point it is the Berry phase effect that suppresses the instanton excitations, causing the deconfinement of spinons. On the other hand, the XY fixed point is found to be stable against instanton excitations because an effective internal charge is zero at the neutral XY fixed point. As a result the deconfinement of spinons occurs at the quantum critical point of the O(3) nonlinear σ model in two dimensions

Critical state in the Y-Ba-Cu-O ceramics

International Nuclear Information System (INIS)

Artemov, A.N.; Grishin, A.M.; Korenivskii, V.N.; Ulyanov, A.N.; Khokhlov, V.A.

1990-01-01

This paper reports on the temperature and field dependences of the Y-Ba-Cu-O ceramics susceptibility studied both experimentally and theoretically. These dependence have been used to reconstruct the temperature dependence of the critical current (j c (T) = j c (O)(1 - T/T c1 ) 3/2 , J c (O) = 340 A/cm 2 , T c1 = 94.6 K) and the distribution of the granules with respect to the superconducting transition temperature (with the maximum at T c2 = 95.3 K and ΔT = 1.1 K). Within the critical state concept diamagnetic response of the granular superconductors at fundamental and multiple frequencies has been calculated. The calculation results are in good agreement with the experimentally obtained susceptibility dependences and explain the different dependences of the diamagnetic response on the magnitude of the d.c. field and the amplitude of a.c. field

Personality factors of critical care nurses.

Science.gov (United States)

Levine, C D; Wilson, S F; Guido, G W

1988-07-01

Two hundred members of the American Association of Critical-Care Nurses responded to a mail-out survey done to determine the psychologic profile of critical care nurses in terms of self-esteem, gender identity, and selected personality characteristics. The instruments used were Cattell's 16 PR, the Personal Attributes Questionnaire (PAQ), and the Texas Social Behavior Inventory (TSBI). Their personality factors tended to be aggressive, assertive, competitive, persevering, moralistic, resourceful, and mechanical. The nurses who enjoyed the field most were of the androgynous or masculine type and had high levels of self-esteem. On the basis of these findings, the nurse recruiter or faculty member doing career counseling could assess the personality characteristics, gender identity, and self-esteem levels of interested nurses. The goal would be to identify nurses who would both enjoy the field and remain active in critical care nursing after orientation. The goal could also be to help nurses dissatisfied with critical care nursing to seek means of improving their self-esteem.

Experimental Study on Critical Power in a Hemispherical Narrow Gap

International Nuclear Information System (INIS)

Park, Rae-Joon; Ha, Kwang-Soon; Kim, Sang-Baik; Kim, Hee-Dong; Jeong, Ji-Hwan

2002-01-01

An experimental study of critical heat flux in gap (CHFG) has been performed to investigate the inherent cooling mechanism in a hemispherical narrow gap. The objectives of the CHFG test are to measure critical power from a critical heat removal rate through the hemispherical narrow gap using distilled water with experimental parameters of system pressure and gap width. The CHFG test results have shown that a countercurrent flow limitation (CCFL) brings about local dryout at the small edge region of the upper part and finally global dryout in a hemispherical narrow gap. Increases in the gap width and pressure lead to an increase in critical power. The measured values of critical power are lower than the predictions made by other empirical CHF correlations applicable to flat plate, annuli, and small spherical gaps. The measured data on critical power in the hemispherical narrow gaps have been correlated using nondimensional parameters with a range of approximately ±20%. The developed correlation has been expanded to apply the spherical geometry using the Siemens/KWU correlation

Needed: Critics of Literacy Education with a More Inclusive Perspective

Directory of Open Access Journals (Sweden)

Joseph Sanacore

2007-02-01

Full Text Available Journalists, book authors, and think tank members have been extremely critical of how literacy is presented in schools. Many of these critics who are inexperienced in literacy education believe that educators are inadequately teaching reading and writing. Those most critical of the “inadequate skills perspective” are usually experts in their respective fields, including neuroscience, speech-language pathology, and educational psychology. Not surprisingly, their fields of expertise are not fine-tuned in the field of literacy. These critics are more likely to promote balanced and constructive criticisms if they (a hold graduate degrees in the areas in which they serve as critics, (b collaborate with colleagues who believe in different points of view, (c maintain rigorous peer-review standards before releasing research findings to the media, (d have practical experience in schools, and (e attend professional development sessions concerning big-picture perspectives and make observations in schools where these perspectives have been effectively implemented.

Neutron reflectivity study of critical adsorption. Application to the understanding of environmental mechanisms

International Nuclear Information System (INIS)

Jestin, Jacques

2001-01-01

This study is within the scope of fundamental knowledge transfer to a field case-study, i.e. the understanding of the adsorption properties of binary mixtures against a wall in the case of soil pollution by liquid hydrocarbons. From the theoretical study of critical adsorption, which has been well described in the literature, we carried out experiments on model systems by using neutron techniques. Neutron reflectivity was then applied to the liquid-vapor interface of three different binary mixtures: perfluorohexane-hexane, deuterated methanol-cyclohexane and methanol-deuterated cyclohexane. The experimental data were analysed according to the theoretical prediction of Fisher and De Gennes, along with Liu and Fisher that suggested a power law decrease of the concentration profile (with an exponent equal to 0.52) followed by an exponential function. The characteristic exponent and the amplitude ratios for the methanol-cyclohexane mixtures were found fitted well with theoretical values for the three systems. Only the perfluorohexane-hexane mixture exhibited a particular behavior in the adsorption process that affected the power law amplitude value. This step allowed us to study non critical adsorption and to apply neutrons techniques, e.g. reflectivity and small angles neutrons scattering, to a water-2,5 dimethylpyridine mixture against silica, which is a model system for soils polluted by water/hydrocarbon mixtures. These experiments highlighted new experimental difficulties, which were not fully solved over this study, together with some problems in the analysis that would require specific modelling. Nevertheless, this study shows the capabilities of neutrons techniques to investigate some environmental mechanisms. Moreover, some of the results reported here can be used as a basis for future experiments. (author)

Administrative Aspects of the Criticality Controls Used in Programmes for Basic Criticality Research, Reactor Development and Materials Processing

Energy Technology Data Exchange (ETDEWEB)

Wood, D. P.; Giessing, D. F. [Operational Safety Division, USAEC Albuquerque Operations Office, NM (United States)

1966-05-15

This paper describes the administrative and procedural aspects of criticality controls used by a field office of the United States Atomic Energy Commission in programmes that include reactor criticals, research and materials testing reactors, and power reactor development. Situations encountered include handling, storing, and processing large quantities of uranium-235 and plutonium-239 of various configurations and compositions in laboratories and operations which gather basic criticality data, processing of fissile material, and varied reactor research and development, programmes including fuel materials. Similar situations exist for uranium-233 and plutonium-238 on a smaller laboratory scale. The administrative controls and interactions of the USAEC field office and the operating contractors, who operate these installations for the USAEC, are outlined. Also, the purpose and scope of the direct examination by USAEC personnel of these contractor facilities are analysed. The programme has been in effect for three years and is believed to be successful in maintaining efficient operations and an acceptable low level of risk of inadvertent criticality. Success of this programme is in good measure due to the close working relationship between the staffs of the USAEC field office and the operating contractors. (author)

From critical phenomena to gauge gields

International Nuclear Information System (INIS)

Le Bellac, M.

1988-01-01

In this book the author gives an introduction to the following questions: critical phenomena (Landau theory, renormalization group, two dimensional models); Perturbation theory and renormalization, scalar euclidian field (Feynman diagrams, Callan-Symanzik equations); Quantum theory of scalar fields (path integrals in quantum mechanics and statistical mechanics, green functions and S matrix, quantization of Klein-Gordon field); Gauge theories (quantization of Dirac field and electromagnetic field, quantum electrodynamics, non-abelian gauge theories) [fr

Critical gases for critical issues: CO2 technologies for oral drug delivery.

Science.gov (United States)

Danan, Hana; Esposito, Pierandrea

2014-02-01

In recent years, CO2-based technologies have gained considerable interest in the pharmaceutical industry for their potential applications in drug formulation and drug delivery. The exploitation of peculiar properties of gases under supercritical conditions has been studied in the last 20 years with mixed results. Promising drug-delivery technologies, based on supercritical CO2, have mostly failed when facing challenges of industrial scaleability and economical viability. Nevertheless, a 'second generation' of processes, based on CO2 around and below critical point has been developed, possibly offering technology-based solutions to some of the current issues of pharmaceutical development. In this review, we highlight the most recent advancements in this field, with a particular focus on the potential of CO2-based technologies in addressing critical issues in oral delivery, and briefly discuss the future perspectives of dense CO2-assisted processes as enabling technologies in drug delivery.

mxCSM: A 100-slit, 6-Wavelength Wide-Field Coronal Spectropolarimeter for the Study of the Dynamics and the Magnetic Fields of the Solar Corona

Energy Technology Data Exchange (ETDEWEB)

Lin, Haosheng, E-mail: lin@ifa.hawaii.edu [Institute for Astronomy, University of Hawaii, Pukalani, HI (United States)

2016-03-30

Tremendous progress has been made in the field of observational coronal magnetometry in the first decade of the Twenty-First century. With the successful construction of the Coronal Multichannel Magnetometer (CoMP) instrument, observations of the linear polarization of the coronal emission lines (CELs), which carry information about the azimuthal direction of the coronal magnetic fields, are now routinely available. However, reliable and regular measurements of the circular polarization signals of the CELs remain illusive. The CEL circular polarization signals allow us to infer the magnetic field strength in the corona, and is critically important for our understanding of the solar corona. Current telescopes and instrument can only measure the coronal magnetic field strength over a small field of view. Furthermore, the observations require very long integration time that preclude the study of dynamic events even when only a small field of view is required. This paper describes a new instrument concept that employs large-scale multiplexing technology to enhance the efficiency of current coronal spectropolarimeter by more than two orders of magnitude. This will allow for the instrument to increase the integration time at each spatial location by the same factor, while also achieving a large field of view coverage. We will present the conceptual design of a 100-slit coronal spectropolarimeter that can observe six CELs simultaneously. Instruments based on this concept will allow us to study the evolution of the coronal magnetic field even with coronagraphs with modest aperture.

Effect of geometry structure on critical properties

Science.gov (United States)

Jiang, Qing; Jiang, Xue-fan

1997-02-01

The effective-field renormalization group (EFRG) scheme is utilized to compute critical properties of the transverse Ising model (TIM) in a quantum-spin system. We distinguish differences between lattices of the same coordination number but of different structures and take effects of the first fluctuation correction into account. The improved results for the critical transverse field are obtained for several lattice structures even by considering the smallest possible cluster, which is in good agreement with series results.

Feminist Scholarship: Cross-Disciplinary Connections for Cultivating a Critical Perspective in Kinesiology

Science.gov (United States)