951 research outputs found
Robin Hood Gardens and the Rehabilitation of Post-War Mass Housing in London
In London, in the context of a shortfall of homes that has achieved the status of “housing crisis”, the replacement of obsolete social housing stock, inherited from the post-war period of mass production, for housing that satisfies the demands of the private market and the need for more sustainable cities is one of the main issues for the 21st century. Robin Hood Gardens’ demolition will become a paradigm for the positions to be taken respecting urban obsolescence. Across London, one can see examples that show how, by the criteria of contemporary urban planning, the domestic and urban potential of much of the post-war social housing stock makes it difficult for the current owner, the local government, to invest in its refurbishment and to keep its status as social housing
“Inside-out Leadership” Toward Developing Efficacious Leaders Among Academic Deans in State Universities and Colleges
Understanding job performance of academic deans is essential to managing organizations. It is therefore significant to find out job performance of the immediate leaders to measure productivity at work. Learning to navigate within the broader organizational environment and the significant changes in the nature of their workmakes academic dean position stressful and difficult. Along the emotional struggles are with a great sense of loneliness and isolation. Academic deans must turn such struggles into enjoyable tasks because they need to man educational organizations and hold responsible of the activities to achieve the goals placed on their hands.The problem of a dean’s multitudinous responsibilities seemed apparent in modern day educational setting. State Universities and Colleges (SUCs) Region III academic deans were not differently far from the academic deans in general. This research regional in scope was done with the aim at finding out the relationship between Inside-out Leadership and Self-efficacy to the Job Performance of Academic Deans in State and Universities and Colleges (SUCs) in Region III for the A.Y. 2016- 2017. The correlational approach was utilized in this study with three questionnaires using RSLQ for Self-efficacy, GSEQ for Self-efficacy, and APR: Dean Evaluation ProcessQuestionnaire for Job Performance as the instruments used in gathering the pertinent data. Findings revealed that ADs were highly efficacious, and were using inside-out strategies to a great extent but the latter skills were not significant to their job performance.
Keywords: inside-out leadership, self-efficacy, academic deans, job performanc
Investigation of the X(5)-Structure in 176Os using Absolute Transition Probabilities
The investigation of the X(5) symmetry in a different mass region from the well established A = 150 region is a very actual topic in nuclear physics. The first example of an X(5) like nucleus, namely 178Os, outside the A = 150 mass region has been found by Moeller et al.[8,51].
From the energy spectrum, the neighbor nucleus 176}Os is considered as a good candidate for a nucleus where the critical point symmetry X(5) [2] can be observed.
The aim of this work is to test the model predictions based on the X(5) critical point symmetry in the 176Os nucleus.
Reliable and precise lifetimes of excited states in 176Os have been measured for the first time using the Recoil Distance Doppler Shift Method. Lifetime experiments were performed at the GASP array, INFN Legnaro and at the FN Tandem accelerator of the University of Cologne in combination with the Cologne plunger apparatus.
In 176Os, the lifetime of eleven excited states were determined using the Differential Decay-Curve Method. In addition, the lifetime of excited states in 177Os were measured. These states were populated in a weaker reaction channel.
In addition two dedicated experiments were performed to remeasure the lifetime of the first excited 2+ states in 176Os and178Os. The aim was to reduce the uncertainty of the B(E2; 2_1+ -> 0_1+) values, which are normally used to normalize transition strength within a nucleus for the comparison with theoretical models.
The comparisons between the experimental transition quadrupole momenta Qt of 176Os derived from the experimental B(E2) strengths and the predictions of the X(5) model confirm the consistency of an X(5)-like description of this nucleus
Using Eye-Tracking to Explore Preference for High Value Visual Stimuli
Eye-tracking is becoming more prevalent in studying various phenomena in psychology. The physiological behavior of eye gaze can reveal psychological processes that may not be conscious. The current study explored whether gaze behavior can be linked to political attitudes. Participants looked at pictures of political candidates with an audio clip of one of their speeches playing as an eye-tracker recorded their gaze behavior. Participants were asked to rate the candidates on an attitude scale. Results showed that only attitudes toward Donald Trump were correlated with gaze duration. In addition, the survey showed that participants gave significantly more extreme answers (either a 1 or a 6) for Trump. This suggests that gaze behavior may correlate only with strong attitudes. This study introduces a possible new way to study attitudes toward visual stimuli
Numerical methods for radiative and ideal relativistic hydrodynamics applied to the study of gamma-ray bursts
This thesis is devoted to the application of high-resolution numerical methods for relativistic hydrodynamics (RHD) to the study of gamma-ray bursts (GRBs), as well as to the development of new schemes able to describe radiative transfer in relativistic magnetized and unmagnetized flows.
On one side, we have performed RHD simulations of relativistic plasma outbursts within the binary-driven hypernova model, developed throughout the last years in the International Center of Relativistic Astrophysics Network (ICRANet). This model is based on the so-called induced gravitational collapse scenario, proposed to explain the observed temporal coincidence of GRBs and supernovae (SN) of type Ic. This scenario considers a carbon-oxigen star (CO core) forming a tight binary system with a companion neutron star (NS). When the collapse of the CO core produces a type Ic SN, part of the ejected material is accreted by the NS, which in turn collapses and forms a black hole (BH). It has been proposed, although the details of this process are a matter of current research, that this collapse creates an optically thick electron-positron plasma around the BH that expands due to its own internal pressure and originates a GRB. Our work in this context has focused on the description of such expanding plasma and its interaction with the surrounding SN ejecta, for which we have followed a hydrodynamical approach using the open-source code PLUTO. This allowed us to study this process in high-density regions that had not been explored thus far, and to perform consistency checks of the model taking into account both theoretical and observational constraints such as the system’s size, the initial plasma energy, the observed timing and the Lorentz factor of the outbursts. Three different scenarios are here considered: (I) the expansion of the plasma in low-density regions, proposed to produce most of the GRB emission in the prompt phase; (II) a model in which X-ray flares are produced due to the breakout of shocks created when the plasma interacts with high-density regions of the SN ejecta; and (III) a model for the emission of secondary bursts due to the creation of reflected waves caused by the same interaction.
The second part of this thesis is devoted to the main part of our work, which consists in the development of a numerical code for radiative transfer integrated in PLUTO. Our implementation is able to solve the equations of relativistic radiation magnetohydrodynamics (Rad-RMHD) under the so-called M1 closure, which allows the radiation transport to be handled in both the free-streaming and diffusion limits. Since we use frequency-averaged opacities, this approach is unable to describe frequency-dependent phenomena; instead, the main focus is put on the transport of total energy and momentum. To avoid numerical instabilities arising due to the possibly large timescale disparity caused by the radiation–matter interaction terms, the Rad-RMHD equations are integrated following implicit–explicit (IMEX) schemes. In this way, interaction terms are integrated implicitly, whereas transport and all of the remaining source terms are solved explicitly by means of the same Godunov-type solvers included in PLUTO. Among these, we have introduced a new Harten–Lax–van Leer–contact (HLLC) solver for optically thin radiation transport. The code is suitable for multidimensional computations in Cartesian, spherical, and cylindrical coordinates using either a single processor or parallel architectures. Adaptive grid computations are also made possible by means of the CHOMBO library. We explain in this work the implementation of all of these methods, after which we show the code’s performance in several problems of radiative transfer in magnetized and unmagnetized flows. We pay particular attention to the behavior of the solutions in the free-streaming and diffusion limits, and show the efficiency and scalability properties of the code as compared with its usual nonradiative implementation. Finally, we show an application of this code to the mentioned model for X-ray flares
No self-shadowing instability in 2D radiation-hydrodynamical models of irradiated protoplanetary disks
Theoretical models of protoplanetary disks including stellar irradiation
often show a spontaneous amplification of scale height perturbations, produced
by the enhanced absorption of starlight in enlarged regions. In turn, such
regions cast shadows on adjacent zones that consequently cool down and shrink,
eventually leading to an alternating pattern of overheated and shadowed
regions. Previous investigations have proposed this to be a real self-sustained
process, the so-called self-shadowing or thermal wave instability, which could
naturally form frequently observed disk structures such as rings and gaps, and
even potentially enhance the formation of planetesimals. All of these, however,
have assumed in one way or another vertical hydrostatic equilibrium and
instantaneous radiative diffusion throughout the disk. In this work we present
the first study of the stability of accretion disks to self-shadowing that
relaxes these assumptions, relying instead on radiation-hydrodynamical
simulations. We first construct hydrostatic disk configurations by means of an
iterative procedure and show that the formation of a pattern of enlarged and
shadowed regions is a direct consequence of assuming instantaneous radiative
diffusion. We then let these solutions evolve in time, which leads to a fast
damping of the initial shadowing features in layers close to the disk surface.
These thermally relaxed layers grow towards the midplane until all temperature
extrema in the radial direction are erased in the entire disk. Our results
suggest that radiative cooling and gas advection at the disk surface prevent a
self-shadowing instability from forming, by damping temperature perturbations
before these reach lower, optically thick regions.Comment: 26 pages, 19 figures. Accepted for publication in ApJ. Complementary
videos can be found in https://youtu.be/RT8IFe8W13
A study on the success of group formation and cohesiveness in virtual teams using computer-mediated communications
While the Internet is a major business tool nowadays, individuals are still challenged to form team s and collaboration virtually. To evaluate the success of team formation in a virtual setting, this research study assessed the role of different computer – mediated communications (CMC) employed on the success of team formation measured by task performance (TP), team cohesiveness (TC), computer skills (CS) and social bond (SB), while assessing the differences on such relationships when controlled for gender, age, education level, academic major, as well as academic year. This research used analysis of variance (ANOVA) and analysis of covariance (ANCOVA) to address the hypotheses proposed. Using three teams and 140 participants, the results indicated that there is a significance difference in the role of CMC levels employed on the level of perception of CS in team formation. Also, there is a significance difference in the role of CMC levels employed on the levels of TP, when controlled for gender .In addition, there is a significance difference in the role of CMC levels employed (No - CMS/F2F,OLS,&OLS+SNS) on the levels of CS, when controlled for education, academic major and academic year. The results of this study contribute to the body of knowledge by helping organizations identify ways to support effective team formations
Acoustic imaging in confined and noisy environments using double layer Time Reversal and Field Separation Methods
International audienceMany imaging methods cannot localize precisely unstationary sources in confined and noisy environments. In this paper, the use of a Time Reversal acoustic sink (TRS) method is proposed, in conjunction with a Field Separation Method (FSM). The proposed time reversal (TR) process is based on the measurement of the sound pressure field and its normal derivative on a double layer hemispherical antenna, which bounds the region of interest (ROI). These data are time-reversed and numerically back-propagated to a surface, 0.5 cm away from the source plane. As most imaging methods, the efficiency of this process relies on the use of the most suitable Green functions, which depend on the propagating environment. A way to improve the TR process is to transform numerically the confined space problem into a free field case, for which the Green functions are well-known. The proposed FSM consists in expanding the measured fields on the spherical harmonics functions, thus allowing to compute the outgoing waves. This process allows a precise localization and characterization of the source placed under the antenna, using free-field Green functions. Thanks to this method, the influence of reverberation and acoustic fields radiated by sources outside the ROI can be suppressed. The measurements presented in this paper are performed in an anechoic room, using two acoustic sources. The first one to image in the ROI emits a filtered pulse and the second one, placed outside the ROI, is driven by a Gaussian white noise. In order to assess the reconstruction quality of the proposed imaging process, a reference field is measured in an anechoic room on the back-propagation surface, corresponding to the pressure values when the source laying in the ROI is radiating alone. Comparisons with back-propagated pressures using TRS in conjunction with FSM show a good accuracy both in space and time domains
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