Influence of organic capping layers on the performance of transparent organic light-emitting diodes

We investigate a set of transparent organic LEDs (TOLEDs) with different organic capping layer (OC) thicknesses to understand the capping layer effect. We find that thickness variation of the OC strongly influences the emission properties of TOLEDs and exhibits different trends for top or bottom emission. The external quantum efficiency for the top side can be enhanced by a factor of 63%, but that of the bottom side only by 4% compared to a reference device without an OC. Additionally, we demonstrate that the introduction of the OC is an effective method to control the bottom-to-top emission ratio within a measured range from 2.87 to 6.05.     

Mixing-induced spontaneous supersymmetry breaking

It is conjectured that flavor mixing furnishes a universal mechanism for the spontaneous breaking of supersymmetry. The conjecture is proved explicitly for the mixing of two chiral N=1 supermultiplets and arguments for its general validity are given. That is an instance of the O?Raifeartaigh Lagrangian for which there is no tree-level nor perturbative breaking. Nonetheless, the dynamical breaking occurs due to the vacuum condensate, a mixing-induced nonperturbative effect that lifts the zero point energy.     

Quantum learning algorithms for quantum measurements

We study quantum learning algorithms for quantum measurements. The optimal learning algorithm is derived for arbitrary von Neumann measurements in the case of training with one or two examples. The analysis of the case of three examples reveals that, differently from the learning of unitary gates, the optimal algorithm for learning of quantum measurements cannot be parallelized, and requires quantum memories for the storage of information.     

On super-linear Emden–Fowler type differential equations

We study the second order Emden–Fowler type differential equation

(a(t)|x^′|^αsgnx^′)^′+b(t)|x|^βsgnx=0${(a(t){\left|x^{\prime }\right|}^{\alpha }\mathrm{sgn}{x}^{\prime })}^{\prime }+b(t){|x|}^{\beta }\mathrm{sgn}x=0$

in the super-linear case α<β$\alpha <\beta$. Using a Hölder-type inequality, we resolve the open problem on the possible coexistence on three possible types of nononscillatory solutions (subdominant, intermediate, and dominant solutions). Jointly with this, sufficient conditions for the existence of globally positive intermediate solutions are established. Some of our results are new also for the Emden–Fowler equation.     

Approximate dynamic programming for stochastic N-stage optimization with application to optimal consumption under uncertainty

Stochastic optimization problems with an objective function that is additive over a finite number of stages are addressed. Although Dynamic Programming allows one to formally solve such problems, closed-form solutions can be derived only in particular cases. The search for suboptimal solutions via two approaches is addressed: approximation of the value functions and approximation of the optimal decision policies. The approximations take on the form of linear combinations of basis functions containing adjustable parameters to be optimized together with the coefficients of the combinations. Two kinds of basis functions are considered: Gaussians with varying centers and widths and sigmoids with varying weights and biases. The accuracies of such suboptimal solutions are investigated via estimates of the error propagation through the stages. Upper bounds are derived on the differences between the optimal value of the objective functional and its suboptimal values corresponding to the use at each stage of approximate value functions and approximate policies. Conditions under which the number of basis functions required for a desired approximation accuracy does not grow “too fast” with respect to the dimensions of the state and random vectors are provided. As an example of application, a multidimensional problem of optimal consumption under uncertainty is investigated, where consumers aim at maximizing a social utility function. Numerical simulations are provided, emphasizing computational pros and cons of the two approaches (i.e., value-function approximation and optimal-policy approximation) using the above-mentioned two kinds of basis functions. To investigate the dependencies of the performances on dimensionality, the numerical analysis is performed for various numbers of consumers. In the simulations, discretization techniques exploiting low-discrepancy sequences are used. Both theoretical and numerical results give insights into the possibility of coping with the curse of dimensionality in stochastic optimization problems whose decision strategies depend on large numbers of variables.     

On the automorphism group of inversive planes of odd order

The structure of the fix bundle free automorphism groups of inversive planes of odd order is determined. As a special case of our main result, the automorphism groups with a transitive action on the points of an inversive plane of odd order are essentially determined, and the plane is shown to be miquelian when these have no non-trivial normal subgroups of odd order.     

Color alteration in teeth subjected to different bleaching techniques

This study evaluated the color alteration of teeth subjected to the action of different bleaching agents and the influence of light sources commonly used in association with these products, In GI, the specimens remained immersed in artificial saliva. The specimens in GII were bleached with a 10% carbamide peroxide gel 4 hours/day during 3 weeks; the teeth in the other three groups were subjected to three sessions of three 10-min applications of 35% hydrogen peroxide gel at 7-day intervals. In GIII, no light was used, while in GIV and GV the gel was associated with a quartz-tungsten-halogen light and a LED/laser source, respectively. The teeth color was evaluated before and 7 days after the bleaching sessions by reflectance spectrophotometry. Data were analyzed statistically by ANOVA and Fisher’s test (α = 0.05), and showed that a significant color change was obtained in all treated groups. After the first week of treatment and at the end of it, the bleaching protocols showed similar results. The results of the present study indicate that association of a light source is not necessary to obtain the bleaching effect and that optimal bleaching can be achieved with all techniques tested.     

Realization of a new experimental setup for magnetostrictive actuators

A new setup for the prospective investigation of the active damping properties of magnetostrictive (MST) actuators has been realized. A dynamical finite element analysis has been carried out to meet the design requirements concerning the eigenvalues spectra and the mode shapes of the setup: experimental and numerical results match satisfactorily. The setup has given a clear evidence of the damping capabilities of a MST actuator developed by our group and utilized as a compensator of external harmonic excitations.