Deriving the exchange times for a model of trap-assisted tunnelling

The work presents a physical model of trap-assisted tunnelling that allows assessing the impact of traps upon the total current through metal/semiconductor heterostructures. The model is based on expressing the occupation probability of the trapping centres by electrons in terms of thermal and tunnelling capture and emission times, commonly referred to as exchange times. The occupation probabilities calculated in this way are then used to evaluate the generation-recombination rates occurring in the continuity equations.

A Maximum-Entropy Method to Estimate Discrete Distributions from Samples Ensuring Nonzero Probabilities

When constructing discrete (binned) distributions from samples of a data set, applications exist where it is desirable to assure that all bins of the sample distribution have nonzero probability. For example, if the sample distribution is part of a predictive model for which we require returning a response for the entire codomain, or if we use Kullback–Leibler divergence to measure the (dis-)agreement of the sample distribution and the original distribution of the variable, which, in the described case, is inconveniently infinite. Several sample-based distribution estimators exist which assure nonzero bin probability, such as adding one counter to each zero-probability bin of the sample histogram, adding a small probability to the sample pdf, smoothing methods such as Kernel-density smoothing, or Bayesian approaches based on the Dirichlet and Multinomial distribution. Here, we suggest and test an approach based on the Clopper–Pearson method, which makes use of the binominal distribution. Based on the sample distribution, confidence intervals for bin-occupation probability are calculated. The mean of each confidence interval is a strictly positive estimator of the true bin-occupation probability and is convergent with increasing sample size. For small samples, it converges towards a uniform distribution, i.e., the method effectively applies a maximum entropy approach. We apply this nonzero method and four alternative sample-based distribution estimators to a range of typical distributions (uniform, Dirac, normal, multimodal, and irregular) and measure the effect with Kullback–Leibler divergence. While the performance of each method strongly depends on the distribution type it is applied to, on average, and especially for small sample sizes, the nonzero, the simple “add one counter”, and the Bayesian Dirichlet-multinomial model show very similar behavior and perform best. We conclude that, when estimating distributions without an a priori idea of their shape, applying one of these methods is favorable.

Excitation probability and effective temperature in the stationary regime of conductivity for Coulomb Glasses

In this paper, we shall illustrate the numerical calculation of the effective temperature in Coulomb glasses by excitation probability provided that the system has been placed in a stationary state after applying a strong electric field. The excitation probability becomes a better alternative than the occupation probability, which has been classically employed to calculate the effective temperature and characterize the thermodynamics of Coulomb glasses out of equilibrium. This is due to the fact that the excitation probability shows better statistics than the occupation probability. In addition, our simulations show that the excitation probability does not depend on the choice of the chemical potential, which critically affects the occupation probability. Our results allow us to propose the excitation probability as a standard procedure to determine the effective temperature in Coulomb glasses as well as in other complex systems such as spin glasses.

Forward Clusters for Degenerate Random Environments

We consider connectivity properties and asymptotic slopes for certain random directed graphs on ℤ2in which the set of points$\mathcal{C}_o$that the origin connects to is always infinite. We obtain conditions under which the complement of$\mathcal{C}_o$has no infinite connected component. Applying these results to one of the most interesting such models leads to an improved lower bound for the critical occupation probability for oriented site percolation on the triangular lattice in two dimensions.

Nest-boxes for Common Swifts Apus apus as compensatory measures in the context of building renovation: efficacy and predictors of occupancy

SummaryCurrently, renovation and thermal insulation of buildings is happening at a high rate in many European countries, driven in part by the political aim to reduce greenhouse gas emissions. Unfortunately, building renovations often lead to a loss of structures, such as accessible cavities, on which synanthropic species, for example house-nesting birds, depend. In Germany, due to legislative regulations, it is a common practice to install nest-boxes as compensation for destroyed nest sites of birds. However, studies on the efficacy of such measures remain sparse. We monitored the occupancy of 477 compensatory nest-boxes for Common Swifts Apus apus, predominantly placed on renovated prefabricated buildings in a city in Germany. We found 24.3% of the boxes occupied by Swifts. On most buildings, the number of occupied boxes was as high as or even higher than the assumed number of breeding sites prior to renovation. Furthermore, in a district where nearly all buildings had been renovated in the past 10 years, we recorded a remarkably high density of Swifts breeding in nest-boxes. Using boosted regression trees, we analysed whether eight different nest-box properties influenced box occupation probability. The number of neighbouring boxes was the most important. Additionally, box age, facade orientation, city district, relative and absolute height, and manner of installation (external/internal) also played a role. Between different nest-box types, we found only negligible differences in occupation probability. Our findings suggest that installing nest-boxes is likely to be an appropriate measure to compensate for nesting sites of Swifts lost during building renovations. Based on our results, we recommend mounting the boxes a few metres apart from each other and close to the roof edge to maximise success. Further studies should be carried out to assess whether our results and conclusions can be confirmed in other situations.

A NOVEL METHOD TO ANALYZE PHASE DIAGRAMS FOR TRAFFICS ON THE CROSSROAD

Traffic flow at a single crossroad consisting of two perpendicular one-lane roads, treated earlier by Ishibashi and Fukui [J. Phys. Soc. Jpn.70, 2793 (2001); 70, 3747 (2001)], has been studied on the basis of the local occupation probability method. However, in this work, based on the novel theoretical analysis and computer simulations, we have studied this crossroad traffic model again and presented the same phase diagrams of traffic flow in the case of various maximum vehicle velocities. We have also derived the flow formulas in all regions in the phase diagrams, which are in good agreement with computer simulation results. Compared with the previous local occupation probability method, our analytical way is simpler and may be widely used for other traffic bottlenecks research.

A MICROSCOPIC PERSPECTIVE ON STRUCTURE OF YRAST BANDS IN 100-112Ru ISOTOPES

The projected shell model (PSM) study of 100 - 112 Ru nuclei is carried out. The reliability of the ground state wave functions is checked by reproducing yrast spectra and electromagnetic properties. The results of calculations indicate that the observed deformation systematics in 100 - 112 Ru isotopes depends on the increase of occupation probability of (1h11/2)ν orbit and the deformation producing tendency of n–p interaction operating between spin orbit partner (SOP) orbits (d5/2)π-(d3/2)ν and (g9/2)π-(g7/2)ν. Besides this, the results on band diagrams show that the yrast spectra in Ru isotopes do not arise from a single intrinsic state only but also from multi-quasiparticle states.