On the Use of Random Set Theory to Bracket the Results of Monte Carlo Simulations

Based on Random Set Theory, procedures are presented for bracketing the results of Monte Carlo simulations in two notable cases: (i) the calculation of the entire distribution of the dependent variable; (ii) the calculation of the CDF of a particular value of the dependent variable (e.g. reliability analyses). The presented procedures are not intrusive in that they can be equally applied when the functional relationship between the dependent variable and independent variables is known analytically and when it is a complex computer model (black box). Also, the proposed procedures can handle probabilistic (with any type of input joint PDF), interval-valued, set-valued, and random set-valued input information, as well as any combination thereof.When exact or outer bounds on the function image can be calculated, the bounds on the CDF of the dependent variable guarantee 100% confidence, and allow for an explicit and exact evaluation of the error involved in the calculation of the CDF. These bounds are often enough to make decisions, and require a minimal amount of functional evaluations. A procedure for effectively approximating the CDF of the dependent variable is also proposed.An example shows that, compared to Monte Carlo simulations, the number of functional evaluations is reduced by orders of magnitude and that the convergence rate increases tenfold.     

Interface Engineering by Thiazolium Iodide Passivation Towards Reduced Thermal Diffusion and Performance Improvement in Perovskite Solar Cells

Interface engineering has become one of the most facile and effective approaches to improve solar cells performance and its long‐term stability and to retard unwanted side reactions. Three passivating agents are developed which can functionalize the surface and induce hydrophobicity, by employing substituted thiazolium iodide (TMI) for perovskite solar cells fabrication. The role of TMI interfacial layers in microstructure and electro‐optical properties is assessed for structural as well as transient absorption measurements. TMI treatment resulted in V_OC and fill factor enhancement by reducing possible recombination paths at the perovskite/hole selective interface and by reducing the shallow as well as deep traps. These in turn allow to achieve higher performance as compared to the pristine surface. Additionally, the TMI passivated perovskite layer considerably reduces CH₃NH₃⁺ thermal diffusion and degradation induced by humidity. The un‐encapsulated perovskite solar cells employing TMI exhibit a remarkable stability under moisture levels (≈50% RH), retaining ≈95% of the initial photon current efficiency after 800 h of fabrication, paving the way towards a potential scalable endeavor.     

A model‐based abstraction layer for heterogeneous SDN applications

Modern controllers for software‐defined networks (SDN) enable the execution of arbitrary SDN applications (eg, Network Address Translation (NAT), traffic monitors) that may be exploited by an overarching set of services (eg, application‐layer orchestrators) to build even richer services. To this purpose, the above overarching services require a mechanism that allows reading the run‐time state and writing the configuration of arbitrary SDN applications, possibly through a uniform API. Unfortunately, most SDN applications are not designed/implemented by taking into account the possibility to be used as part of higher level service workflows (eg, a complex intrusion prevention system that leverages multiple elementary services as individual components), hence they may not provide an adequate interface that would allow overarching services to exploit their features. This paper addresses this problem by proposing an approach to represent the run‐time state of arbitrary applications, where data are exported according to high‐level model‐based structures. Furthermore, the mapping from the high‐level data model to the actual data representation within the SDN application is enabled by a suite of algorithms that are generic enough to operate independently of the actual source code of the application, thus avoiding undesired and invasive modifications to existing applications. The paper also presents a software framework and a prototype implementing the proposed approach, characterizes the resulting performance, and discusses pros and cons of the proposed approach.     

Perceiving surface slant from deformation of optic flow.

Perceived surface orientation and angular velocity were investigated for orthographic projections of 3-D rotating random-dot planes. It was found that (a) tilt was accurately perceived and (b) slant and angular velocity were systematically misperceived. It was hypothesized that these misperceptions are the product of a heuristic analysis based on the deformation, one of the differential invariants of the first-order optic flow. According to this heuristic, surface attitude and angular velocity are recovered by determining the magnitudes of these parameters that most likely produce the deformation of the velocity field, under the assumption that all slant and angular velocity magnitudes have the same a priori probability. The results of the present investigation support this hypothesis. Residual orientation anisotropies not accounted for by the proposed heuristic were also found. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Numerical Study of the Effect of Verification Core Hole on the Point Bearing Capacity of Drilled Shafts

This paper presents a numerical investigation of the effect of a verification core hole on the point bearing capacity of drilled shafts installed in clay shales. The verification core extracted at the shaft tip may reduce the point bearing capacity of drilled shafts as a result of degradation of clay shales and imperfect core hole infill. Finite-element analyses were conducted using the Mohr-Coulomb model with total stress material parameters estimated from laboratory tests. A series of load-displacement curves was calculated for 1 cycle of air drying and wetting; different drying durations and different core hole conditions were considered; and the point bearing capacity was determined at 3 and 5% shaft diameter displacements. The numerical analyses indicate that the point bearing capacity of drilled shafts with a verification core hole does not decrease for most cases, and the maximum reduction merely reaches 5%. Recommendations are made to reduce the effect of the verification core extracted at the shaft bottom during construction.     

Chemical mapping of individual semiconductor nanostructures

We demonstrate experimentally the power of a novel analytical tool for X-ray spectromicroscopy. This provides a minimally intrusive elemental mapping of surfaces at the nanoscale and holds the promise of remarkable versatility. We have applied our procedure to the characterization of Ge(Si) islands on Si(111) substrates, with the aim of investigating the surface stoichiometry gradients and gaining insight into the intermixing dynamics. By identifying Si-richer edges with respect to the centers, we are able to associate alloying in these islands to surface transport processes.     

Sudden unexpected death in patients with epilepsy receiving renal replacement therapy with dialysis: a 17-year experience at a single institution

Epilepsy is the most common acquired chronic neurological disorder; each year about 1 in a 1000 patients with chronic epilepsy die suddenly, unexpectedly, and without explanation, even with postmortem examination (SUDEP). Seizure incidence is approximately 10% in patients with chronic renal failure and hemodialysis-associated seizure has been considered to be a common complication of people on hemodialysis treatment. Considering this, we evaluated the incidence of seizures in 189 patients under dialytic treatment.     

Alternative Resilience Indices for City Ecosystems Subjected to Natural Hazards

Prompt and efficient responses against natural hazards are needed to build cities capable of withstanding disasters, namely resilient cities. This study aims at presenting and testing synthetic resilience indices over a real urban center threatened by multiple hazards, for which a global overview of city performance is requested. An integrated framework is proposed for quantitative resilience assessment by way of time‐independent synthetic indices. The approach proposed is in accordance to the complex network theory and uses a global indicator of the system connectivity to assess the city functioning also in case of network disruption. Resilience is evaluated as a proxy for systemic urban damage by modeling a city ecosystem as a hybrid social–physical network. Seismic and landslide scenario analyses are performed for the city of Sarno, Italy. A probability‐based approach is used to compute urban vulnerability. Subsequently, to highlight changes in results according to the type of disaster, a recovery strategy is simulated to assess efficiency and damage states in each recovery stage, and urban resilience.     

Enantioselective hydrolysis of some 2-aryloxyalkanoic acid methyl esters and isosteric analogues using a penicillin G acylase-based HPLC monolithic silica column

A technique based on liquid chromatography has been developed to facilitate studies of enantioselectivity in penicillin G acylase (PGA)-catalyzed hydrolysis of some 2-aryloxyalkanoic acid methyl esters and isosteric analogues. PGA was covalently immobilized on an aminopropyl monolithic silica support to create an immobilized HPLC-enzyme reactor. Two sets of experimental data were drawn to calculate the enantioselectivity (E) of the kinetically controlled enantiomer-differentiating reaction, the degree of substrate conversion and the enantiomeric excess of the product. The developed enzymatic reactor was coupled through a switching valve to an achiral analytical column for separation and quantitation of the hydrolysis products. The enantiomeric excess was determined off-line on a PGA-chiral stationary phase. In this way, highly precise E values were determined. A computational study related to the hydrolysis of the considered racemic esters was also carried out in order to unambiguously clarify both the substrate specificity and the enantioselectivity displayed by PGA.     

Analysis of a contention resolution multiple-access algorithm for handling mixed traffic on wireless networks

Existing wireless standards, like DECT and GSM, are based on TDMA. Packet multiple-access algorithms perform statistical multiplexing, leading to greater efficiency than basic TDMA which assigns a fixed amount of channel resources to each user. Moreover, these methods permit one to handle in a more flexible way different kinds of information. Most of the proposed packet access methods, applied to radio networks, are based on slotted ALOHA algorithms. We propose a methodology for applying packet contention resolution multiple-access techniques to wireless networks. The proposed techniques are able to handle the access of mixed traffic types. We define and analyze a multiple-access algorithm for handling the access of a mixed set of users, including a group of speech users and a population of users that generate a random traffic approximated by a stream of Poisson.