Mode I crack tip fields: strain gradient plasticity theory versus J2 flow theory

The mode I crack tip asymptotic response of a solid characterised by strain gradient plasticity is investigated. It is found that elastic strains dominate plastic strains near the crack tip, and thus the Cauchy stress and the strain state are given asymptotically by the elastic K-field. This crack tip elastic zone is embedded within an annular elasto-plastic zone. This feature is predicted by both a crack tip asymptotic analysis and a finite element computation. When small scale yielding applies, three distinct regimes exist: an outer elastic K field, an intermediate elasto-plastic field, and an inner elastic K field. The inner elastic core significantly influences the crack opening profile. Crack tip plasticity is suppressed when the material length scale $\ell$ of the gradient theory is on the order of the plastic zone size estimation, as dictated by the remote stress intensity factor. A generalized J-integral for strain gradient plasticity is stated and used to characterise the asymptotic response ahead of a short crack. Finite element analysis of a cracked three point bend specimen reveals that the crack tip elastic zone persists in the presence of bulk plasticity and an outer J-field

Successful Leadership: Optimizing the Influence of Personality on Work Engagement

Abstract Objective: This paper examines the positive influence that personality has on the level of engagement workers have in their work. By determining the connection between personality characteristics and work engagement, leaders can be proactive in promoting higher levels of engagement by their workers. Background: Engaging in one’s work encompasses the total person and includes elements such as energy, mental resilience, willingness to invest in one’s work, enthusiasm, pride, and the happiness that comes with being involved in work. The level of work engagement of workers in their work has implications for the workers as well as for the organization. Method: Through a review of literature related to personality characteristics and work engagement, the personality characteristics having a positive influence on work engagement are identified. Along with these characteristics, the practical actions associated with these characteristics that have been shown to promote work engagement are discussed. Results: On the basis of literature reviewed, the personality characteristics of conscientiousness, extraversion, and proactive personality were found to have a positive influence on work engagement. Associated with these personality characteristics are a variety of practical actions that impact work engagement. Conclusion: The connection between personality characteristics and engagement in work has been identified. Utilizing practical actions that have been shown to be a positive influence on work engagement is beneficial for the workers as well as for the organization. Application: Leaders can achieve higher levels of success by utilizing the practical actions associated with certain personality characteristics to promote higher levels of work engagement among workers

Züchtungsmethoden in der Diskussion - Brauchen wir Kohl aus Protoplastenfusion?

Bei Kohl aus ökologischem Anbau scheiden sich die Bio-Geister: Kohrabi-, Brokkoli- und Blumenkohlsorten aus Europa und den USA werden zunehmend mit Hilfe umstrittener Züchtungsmethoden wie der gentechnik-nahen Protoplastenfusion angebaut. Werte des Ökolandbaus wie der Erhalt der Artenvielfalt und der Schutz der natürlichen Reproduktionsfähigkeit von Pflanzen werden durch solche Techniken in Frage gestellt. Warum und mit welchem Nutzen sich diese Züchtungsmethode in den letzten Jahren im Gemüseanbau etabliert hat, wird von Fachleuten unterschiedlich beantwortet. Nur mit welchen Konsequenzen? Was sind die Alternativen für Anbau und Handel? Die Protoplastenfusion wird bei Kohl angewendet, um die erbliche Pollensterilität (cytoplasmatic male sterility = CMS) des Rettichs auf verschiedene Kohlarten zu übertragen. Sie erleichtert die Züchtung von Hybriden, die mittlerweile auch im Öko-Landbau weit verbreitet sind - unverdientermaßen, aber das wäre ein weiteres Diskussionsthema..

Spectroscopy of doubly charmed baryons

We study the mass spectrum of baryons with two and three charmed quarks. For double charm baryons the spin splitting is found to be smaller than standard quark-model potential predictions. This splitting is not influenced either by the particular form of the confining potential or by the regularization taken for the contact term of the spin-spin potential. We consistently predict the spectra for triply charmed baryons.Comment: 6 pages, 1 figure, accepted for publication in Phys. Rev.

Smart Content Recognition from Images Using a Mixture of Convolutional Neural Networks

With rapid development of the Internet, web contents become huge. Most of the websites are publicly available, and anyone can access the contents from anywhere such as workplace, home and even schools. Nevertheless, not all the web contents are appropriate for all users, especially children. An example of these contents is pornography images which should be restricted to certain age group. Besides, these images are not safe for work (NSFW) in which employees should not be seen accessing such contents during work. Recently, convolutional neural networks have been successfully applied to many computer vision problems. Inspired by these successes, we propose a mixture of convolutional neural networks for adult content recognition. Unlike other works, our method is formulated on a weighted sum of multiple deep neural network models. The weights of each CNN models are expressed as a linear regression problem learned using Ordinary Least Squares (OLS). Experimental results demonstrate that the proposed model outperforms both single CNN model and the average sum of CNN models in adult content recognition.Comment: To be published in LNEE, Code: github.com/mundher/NSF

Channeling 5-min photospheric oscillations into the solar outer atmosphere through small-scale vertical magnetic flux tubes

We report two-dimensional MHD simulations which demonstrate that photospheric 5-min oscillations can leak into the chromosphere inside small-scale vertical magnetic flux tubes. The results of our numerical experiments are compatible with those inferred from simultaneous spectropolarimetric observations of the photosphere and chromosphere obtained with the Tenerife Infrared Polarimeter (TIP) at 10830 A. We conclude that the efficiency of energy exchange by radiation in the solar photosphere can lead to a significant reduction of the cut-off frequency and may allow for the propagation of the 5 minutes waves vertically into the chromosphere.Comment: accepted by ApJ

One-dimensional metallic behavior of the stripe phase in La2−x_{2-x}Srx_xCuO4_4

Using an exact diagonalization method within the dynamical mean-field theory we study stripe phases in the two-dimensional Hubbard model. We find a crossover at doping $\delta\simeq 0.05$ from diagonal stripes to vertical site-centered stripes with populated domain walls, stable in a broad range of doping, $0.05<\delta<0.17$. The calculated chemical potential shift $\propto -\delta^2$ and the doping dependence of the magnetic incommensurability are in quantitative agreement with the experimental results for doped La$_{2-x}$Sr$_x$CuO$_4$. The electronic structure shows one-dimensional metallic behavior along the domain walls, and explains the suppression of spectral weight along the Brillouin zone diagonal.Comment: 4 pages, 4 figure

Pattern formation during diffusion limited transformations in solids

We develop a description of diffusion limited growth in solid-solid transformations, which are strongly influenced by elastic effects. Density differences and structural transformations provoke stresses at interfaces, which affect the phase equilibrium conditions. We formulate equations for the interface kinetics similar to dendritic growth and study the growth of a stable phase from a metastable solid in both a channel geometry and in free space. We perform sharp interface calculations based on Green's function methods and phase field simulations, supplemented by analytical investigations. For pure dilatational transformations we find a single growing finger with symmetry breaking at higher driving forces, whereas for shear transformations the emergence of twin structures can be favorable. We predict the steady state shapes and propagation velocities, which can be higher than in conventional dendritic growth.Comment: submitted to Philosophical Magazin

Spin correlations in Ca3Co2O6: A polarised-neutron diffraction and Monte Carlo study

We present polarised-neutron diffraction measurements of the Ising-like spin-chain compound Ca3Co2O6 above and below the magnetic ordering temperature TN. Below TN, a clear evolution from a single-phase spin-density wave (SDW) structure to a mixture of SDW and commensurate antiferromagnet (CAFM) structures is observed on cooling. For a rapidly-cooled sample, the majority phase at low temperature is the SDW, while if the cooling is performed sufficiently slowly, then the SDW and the CAFM structure coexist between 1.5 and 10 K. Above TN, we use Monte Carlo methods to analyse the magnetic diffuse scattering data. We show that both intra- and inter-chain correlations persist above TN, but are essentially decoupled. Intra-chain correlations resemble the ferromagnetic Ising model, while inter-chain correlations resemble the frustrated triangular-lattice antiferromagnet. Using previously-published bulk property measurements and our neutron diffraction data, we obtain values of the ferromagnetic and antiferromagnetic exchange interactions and the single-ion anisotropy.Comment: 10 pages, 7 figure