Photonic realization of the relativistic Dirac oscillator

A photonic realization of the Dirac oscillator (DO), i.e. of the relativistic extension of the quantum harmonic oscillator, is proposed for light propagation in fiber Bragg gratings. Transmission spectra clearly show the existence of electron and positron bound states of the DO, corresponding to resonance modes above and below the Bragg frequency, as well as the asymmetry of the energy spectrum for electron and positron branches

The influence of an external magnetic field on the dynamic stress of an elastic conducting one-sided layer with a longitudinal shear crack

We study the interaction of a magnetoelastic shear wave with a curvilinear tunnel crack in an ideally conducting diamagnetic (resp. paramagnetic) one-sided (resp. two-sided) layer in the presence of an external static magnetic field. The bases of the one-sided layer are free of mechanical load, and the rim of the face is clamped or free. The corresponding linearized boundary-value problem of magnetoelasticity is reduced to a singular integrodifferential equation with subsequent implementation on a computer. We give numerical results that characterize the influence of the size of the preliminary magnetic field, the frequencies of the load, the curvature, and the orientation of the crack on the stress intensity factor. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2163

Regularized reconstruction in quantitative SPECT using CT side information from hybrid imaging

A penalized-likelihood (PL) SPECT reconstruction method using a modified regularizer that accounts for anatomical boundary side information was implemented to achieve accurate estimates of both the total target activity and the activity distribution within targets. In both simulations and experimental I-131 phantom studies, reconstructions from (1) penalized likelihood employing CT-side information-based regularization (PL-CT), (2) penalized likelihood with edge preserving regularization (no CT) and (3) penalized likelihood with conventional spatially invariant quadratic regularization (no CT) were compared with (4) ordered subset expectation maximization (OSEM), which is the iterative algorithm conventionally used in clinics for quantitative SPECT. Evaluations included phantom studies with perfect and imperfect side information and studies with uniform and non-uniform activity distributions in the target. For targets with uniform activity, the PL-CT images and profiles were closest to the 'truth', avoided the edge offshoots evident with OSEM and minimized the blurring across boundaries evident with regularization without CT information. Apart from visual comparison, reconstruction accuracy was evaluated using the bias and standard deviation (STD) of the total target activity estimate and the root mean square error (RMSE) of the activity distribution within the target. PL-CT reconstruction reduced both bias and RMSE compared with regularization without side information. When compared with unregularized OSEM, PL-CT reduced RMSE and STD while bias was comparable. For targets with non-uniform activity, these improvements with PL-CT were observed only when the change in activity was matched by a change in the anatomical image and the corresponding inner boundary was also used to control the regularization. In summary, the present work demonstrates the potential of using CT side information to obtain improved estimates of the activity distribution in targets without sacrificing the accuracy of total target activity estimation. The method is best suited for data acquired on hybrid systems where SPECT-CT misregistration is minimized. To demonstrate clinical application, the PL reconstruction with CT-based regularization was applied to data from a patient who underwent SPECT/CT imaging for tumor dosimetry following I-131 radioimmunotherapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85409/1/pmb10_9_007.pd

Convex optimization problem prototyping for image reconstruction in computed tomography with the Chambolle-Pock algorithm

The primal-dual optimization algorithm developed in Chambolle and Pock (CP), 2011 is applied to various convex optimization problems of interest in computed tomography (CT) image reconstruction. This algorithm allows for rapid prototyping of optimization problems for the purpose of designing iterative image reconstruction algorithms for CT. The primal-dual algorithm is briefly summarized in the article, and its potential for prototyping is demonstrated by explicitly deriving CP algorithm instances for many optimization problems relevant to CT. An example application modeling breast CT with low-intensity X-ray illumination is presented.Comment: Resubmitted to Physics in Medicine and Biology. Text has been modified according to referee comments, and typos in the equations have been correcte

Family motivation of supervisors: Exploring the impact on subordinates’ work performance via family supportive supervisor behaviors and work–family balance satisfaction

Family supportive supervisor behaviors (FSSB) have emerged as a powerful resource of informal support for the well-being and development of employees. However, research to date offers limited insight into the antecedents and underlying processes that may trigger FSSBs. We investigate the association between family motivation of supervisors and FSSBs, and how the latter mediates the association between supervisors’ family motivation and subordinates’ work performance. Furthermore, we examine the role of supervisors’ satisfaction with their work–family balance as a contextual variable influencing our proposed associations. We draw on FSSB and perspective taking theory as over-arching frameworks for our hypotheses. Using matched and multisource supervisor-subordinate data collected from an organization in Chile (196 subordinates and 75 supervisors), our findings revealed that FSSBs are mechanisms linking supervisors’ family motivation to subordinates’ work performance. Interestingly, this positive association is moderated by supervisors’ satisfaction with their work–family balance, such that the mediation of FSSBs is stronger for supervisors who are not satisfied with their work–family balance

Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers

Cataloged from PDF version of article.We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. (C) 2011 Optical Society of Americ

Family motivation of supervisors: Exploring the impact on subordinates’ work performance via family supportive supervisor behaviors and work–family balance satisfaction

Family supportive supervisor behaviors (FSSB) have emerged as a powerful resource of informal support for the well-being and development of employees. However, research to date offers limited insight into the antecedents and underlying processes that may trigger FSSBs. We investigate the association between family motivation of supervisors and FSSBs, and how the latter mediates the association between supervisors’ family motivation and subordinates’ work performance. Furthermore, we examine the role of supervisors’ satisfaction with their work–family balance as a contextual variable influencing our proposed associations. We draw on FSSB and perspective taking theory as over-arching frameworks for our hypotheses. Using matched and multisource supervisor-subordinate data collected from an organization in Chile (196 subordinates and 75 supervisors), our findings revealed that FSSBs are mechanisms linking supervisors’ family motivation to subordinates’ work performance. Interestingly, this positive association is moderated by supervisors’ satisfaction with their work–family balance, such that the mediation of FSSBs is stronger for supervisors who are not satisfied with their work–family balance

Diffusive and localization behavior of electromagnetic waves in a two-dimensional random medium

In this paper, we discuss the transport phenomena of electromagnetic waves in a two-dimensional random system which is composed of arrays of electrical dipoles, following the model presented earlier by Erdogan, et al. (J. Opt. Soc. Am. B {\bf 10}, 391 (1993)). A set of self-consistent equations is presented, accounting for the multiple scattering in the system, and is then solved numerically. A strong localization regime is discovered in the frequency domain. The transport properties within, near the edge of and nearly outside the localization regime are investigated for different parameters such as filling factor and system size. The results show that within the localization regime, waves are trapped near the transmitting source. Meanwhile, the diffusive waves follow an intuitive but expected picture. That is, they increase with travelling path as more and more random scattering incurs, followed by a saturation, then start to decay exponentially when the travelling path is large enough, signifying the localization effect. For the cases that the frequencies are near the boundary of or outside the localization regime, the results of diffusive waves are compared with the diffusion approximation, showing less encouraging agreement as in other systems (Asatryan, et al., Phys. Rev. E {\bf 67}, 036605 (2003).)Comment: 8 pages 9 figure

Metoda za raspodjelu pogonske sile električnih vozila sa četiri kotača na kratkotrajno ili polovično skliskim cestama

In this paper, a four-wheel driving force distribution method based on driving force control is proposed. Driving force control is an anti-slip control method, previously proposed by the authors’ research group, which generates appropriate driving force based on the acceleration pedal. However, this control method cannot completely prevent reduction of driving force when a vehicle runs on an extremely slippery road. If the length of a slippery surface is shorter than the vehicle’s wheel base, the total driving force is retained by distributing the shortage of driving force to the wheels that still have traction. On the other hand, when either the left or right side runs on a slippery surface, yaw-moment is suppressed by setting total driving forces of left and right wheels to be the same. Therefore, four-wheel driving force distribution method is proposed for retaining driving force on instantaneous slippery roads, and suppressing yaw-moment on split ones. The effectiveness of the proposed distribution method is verified by simulations and experiments.U ovom radu predložena je metoda za raspodjelu pogonske sile električnih vozila sa četiri kotača temeljena na upravljanju pogonskom silom. Upravljanje pogonskom silom je metoda upravljanja koju je ranije predložila autorova istraživačka grupa, a koristi se za sprječavanje proklizavanja. Ova metoda generira prikladnu pogonsku silu temeljem pritiska na papučicu ubrzanja. Ipak, ova metoda upravljanja ne može u potpunosti spriječiti smanjenje pogonske sile kada vozilo nai.e na ekstremno sklisku cestu. Ako je dužina skliske površine kraća od me.uosovinskog razmaka vozila, ukupna pogonska sila se zadržava redistribucijom manjka pogonske sile na kotače koji i dalje imaju trakciju. S druge strane, kada lijeva ili desna strana vozila nai.e na sklisku površinu, moment zakretanja se potiskuje postavljanjem ukupne pogonske sile lijevih i desnih kotača na jednaki iznos. Dakle, metoda za raspodjelu pogonske sile predložena je za zadržavanje pogonske sile na kratkotrajno skliskim cestama, te za sprječavanje momenta zakretanja na polovično skliskim cestama. Učinkovitost predložene metode verificirana je simulacijski i eksperimentalno