DFT study of oxygen-bridged Zn2+ ion pairs in Zn/ZSM-5 zeolites

A cluster model for Zn/ZSM-5 zeolite is proposed, which consists of an oxygen-bridged [Zn–O–Zn]²⁺ moiety attached to two framework aluminum ions of two adjacent ZSM-5 5-rings. Its stability and catalytic activity in ethane dehydrogenation were considered using the DFT method and compared with those for single Zn²⁺ ions in the same rings. It is shown that the oxygen-bridged Zn²⁺ pair is rather reactive towards ethane dissociation and that the rate-limiting step is release of hydrogen.     

Comparison of Non-Equilibrium Green’s Function and Quantum-Corrected Monte Carlo Approaches in Nano MOS Simulation

In this paper, we present a comparative study between non-equilibrium Green’s function and quantum-corrected Monte Carlo approaches for an ultra-short channel MOSFET. As a result, we have found that the both models are equivalent in the simulation of quantum transport in a nano-scale MOSFET. We will also demonstrate that impurity scattering in the source region and plasmon scattering at the drain-end of the channel especially influence the drain current based on the quantum-corrected Monte Carlo approach.     

Angle- and size-dependent characteristics of incoherent Raman and fluorescent scattering by microspheres. 2. Numerical simulation

The results of numerical simulation of inelastic scattering by microspheres with the use of a dipole model are presented. The formulas that are derived speed up the computation, thereby permitting larger-sized microspheres to be studied. The angular scattering cross section and depolarization are calculated for a wide range of size parameters as well as for different orientations of incident wave polarization. Calculations performed with small incremental changes in size permit the influence of morphology-dependent resonance (MDR) on the power and angular distribution of scattered radiation to be studied. TM and TE types of MDR produce enhanced scattering of the incident wave with vertical and horizontal polarization; the corresponding shape of the phase function becomes oscillatory. Special attention is paid to the simulation of backward scattering by water droplets, which is important for Raman lidar applications.     

Observation of3He crystal nucleation from the superfluid phases

A CCD camera operating at T = 65 K was mounted in the vacuum space of our nuclear demagnetization cryostat. This has allowed us to make observations of³He crystals at temperatures below the superfluid phase transitions, in contrast to direct optical observations, which have so far been limited to T 20 mK.1 The good thermal equilibrium provided by the superfluid allows us to nucleate single crystals of³He in the region of the cell visible to the optical system. This occurs either spontaneously (due either to gravitational pressure gradients or local surface defects) or as a result of a small applied heat pulse.     

Sensitivity analysis of LP-MPC cascade control systems

Model predictive control (MPC) has found wide application in the chemical process industry as well as other industrial sectors. Commercial MPC systems are typically implemented in conjunction with a steady-state linear or quadratic programming optimizer, whose key functions are to track the economic optimum and to provide feasible set-points to the model predictive controller. The two-level system is complementary to real-time optimization which typically utilizes more complex models and is executed less frequently. Despite the widespread adoption of LP-MPC systems, occurrences of poor performance have been reported, where large variations in the computed set-points were observed. In this paper, we analyze the sensitivity of the LP solution to variation in the LP model bias, through which feedback to the LP layer occurs. We consider both multi-input, single-output (MISO) and multi-input, multi-output (MIMO) systems. Principles are illustrated through graphical representation as well as case studies. The performance of the two-level LP-MPC closed-loop system is evaluated and explained using results of the LP sensitivity analysis.     

Parameterized code SHARM-3D for radiative transfer over inhomogeneous surfaces

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima-Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom.     

Neural integrator: a sandpile model

We investigated a model for the neural integrator based on hysteretic units connected by positive feedback. Hysteresis is assumed to emerge from the intrinsic properties of the cells. We consider the recurrent networks containing either bistable or multistable neurons. We apply our analysis to the oculomotor velocity-to-position neural integrator that calculates eye positions using the inputs that carry information about eye angular velocity. By analyzing this system in the parameter space, we show the following. The direction of hysteresis in the neuronal response may be reversed for the system with recurrent connections compared to the case of unconnected neurons. Thus, for the NMDA receptor-based bistability, the firing rates after ON saccades may be higher than after OFF saccades for the same eye position. The reversal of hysteresis occurs in this model only when the size of hysteresis differs from neuron to neuron. We also relate the macroscopic leak time constant of the integrator to the rate of microscopic spontaneous noise-driven transitions in the hysteretic units. Finally, we investigate the conditions under which the hysteretic integrator may have no threshold for integration.     

Implementation of the iterative finite-difference time-domain technique for simulation of periodic structures at oblique incidence

In this paper we review a recently developed finite-difference time-domain (FDTD) iterative technique for the analysis of periodic structures at oblique incidence. We show how it can be implemented in FDTD code and estimate required computer memory and time resources. To illustrate performance of our technique we demonstrate the plasmon formation in a thin gold film placed at air/glass interface and calculate reflectance from silicon textured coating at oblique incidence.     

Correction to: Network Effects of International Shocks and Spillovers

Networks and Spatial Economics - The original version of the article unfortunately contained a mistake. The Annex table was distorted and some columns were out of order. The corrected version is...